* [PATCH v3 01/52] CPU hotplug: Add lockdep annotations to get/put_online_cpus()
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
@ 2014-03-10 20:34 ` Srivatsa S. Bhat
2014-03-10 20:34 ` [PATCH v3 02/52] CPU hotplug: Provide lockless versions of callback registration functions Srivatsa S. Bhat
` (52 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:34 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, Gautham R. Shenoy, walken, linux, linux-pm,
linux-kernel, linuxppc-dev, Srivatsa S. Bhat, tj, paulmck,
Ingo Molnar
From: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Add lockdep annotations for get/put_online_cpus() and
cpu_hotplug_begin()/cpu_hotplug_end().
Cc: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
kernel/cpu.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/kernel/cpu.c b/kernel/cpu.c
index deff2e6..33caf5e 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -19,6 +19,7 @@
#include <linux/mutex.h>
#include <linux/gfp.h>
#include <linux/suspend.h>
+#include <linux/lockdep.h>
#include "smpboot.h"
@@ -57,17 +58,30 @@ static struct {
* an ongoing cpu hotplug operation.
*/
int refcount;
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+ struct lockdep_map dep_map;
+#endif
} cpu_hotplug = {
.active_writer = NULL,
.lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
.refcount = 0,
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+ .dep_map = {.name = "cpu_hotplug.lock" },
+#endif
};
+/* Lockdep annotations for get/put_online_cpus() and cpu_hotplug_begin/end() */
+#define cpuhp_lock_acquire_read() lock_map_acquire_read(&cpu_hotplug.dep_map)
+#define cpuhp_lock_acquire() lock_map_acquire(&cpu_hotplug.dep_map)
+#define cpuhp_lock_release() lock_map_release(&cpu_hotplug.dep_map)
+
void get_online_cpus(void)
{
might_sleep();
if (cpu_hotplug.active_writer == current)
return;
+ cpuhp_lock_acquire_read();
mutex_lock(&cpu_hotplug.lock);
cpu_hotplug.refcount++;
mutex_unlock(&cpu_hotplug.lock);
@@ -87,6 +101,7 @@ void put_online_cpus(void)
if (!--cpu_hotplug.refcount && unlikely(cpu_hotplug.active_writer))
wake_up_process(cpu_hotplug.active_writer);
mutex_unlock(&cpu_hotplug.lock);
+ cpuhp_lock_release();
}
EXPORT_SYMBOL_GPL(put_online_cpus);
@@ -117,6 +132,7 @@ void cpu_hotplug_begin(void)
{
cpu_hotplug.active_writer = current;
+ cpuhp_lock_acquire();
for (;;) {
mutex_lock(&cpu_hotplug.lock);
if (likely(!cpu_hotplug.refcount))
@@ -131,6 +147,7 @@ void cpu_hotplug_done(void)
{
cpu_hotplug.active_writer = NULL;
mutex_unlock(&cpu_hotplug.lock);
+ cpuhp_lock_release();
}
/*
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 02/52] CPU hotplug: Provide lockless versions of callback registration functions
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
2014-03-10 20:34 ` [PATCH v3 01/52] CPU hotplug: Add lockdep annotations to get/put_online_cpus() Srivatsa S. Bhat
@ 2014-03-10 20:34 ` Srivatsa S. Bhat
2014-03-10 20:34 ` [PATCH v3 03/52] Doc/cpu-hotplug: Specify race-free way to register CPU hotplug callbacks Srivatsa S. Bhat
` (51 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:34 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, Peter Zijlstra,
Rafael J. Wysocki, linux-kernel, Ingo Molnar, linuxppc-dev,
Srivatsa S. Bhat, Oleg Nesterov, tj, Toshi Kani, Thomas Gleixner,
paulmck, Andrew Morton
The following method of CPU hotplug callback registration is not safe
due to the possibility of an ABBA deadlock involving the cpu_add_remove_lock
and the cpu_hotplug.lock.
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
The deadlock is shown below:
CPU 0 CPU 1
----- -----
Acquire cpu_hotplug.lock
[via get_online_cpus()]
CPU online/offline operation
takes cpu_add_remove_lock
[via cpu_maps_update_begin()]
Try to acquire
cpu_add_remove_lock
[via register_cpu_notifier()]
CPU online/offline operation
tries to acquire cpu_hotplug.lock
[via cpu_hotplug_begin()]
*** DEADLOCK! ***
The problem here is that callback registration takes the locks in one order
whereas the CPU hotplug operations take the same locks in the opposite order.
To avoid this issue and to provide a race-free method to register CPU hotplug
callbacks (along with initialization of already online CPUs), introduce new
variants of the callback registration APIs that simply register the callbacks
without holding the cpu_add_remove_lock during the registration. That way,
we can avoid the ABBA scenario. However, we will need to hold the
cpu_add_remove_lock throughout the entire critical section, to protect updates
to the callback/notifier chain.
This can be achieved by writing the callback registration code as follows:
cpu_maps_update_begin(); [ or cpu_notifier_register_begin(); see below ]
for_each_online_cpu(cpu)
init_cpu(cpu);
/* This doesn't take the cpu_add_remove_lock */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_maps_update_done(); [ or cpu_notifier_register_done(); see below ]
Note that we can't use get_online_cpus() here instead of cpu_maps_update_begin()
because the cpu_hotplug.lock is dropped during the invocation of CPU_POST_DEAD
notifiers, and hence get_online_cpus() cannot provide the necessary
synchronization to protect the callback/notifier chains against concurrent
reads and writes. On the other hand, since the cpu_add_remove_lock protects
the entire hotplug operation (including CPU_POST_DEAD), we can use
cpu_maps_update_begin/done() to guarantee proper synchronization.
Also, since cpu_maps_update_begin/done() is like a super-set of
get/put_online_cpus(), the former naturally protects the critical sections
from concurrent hotplug operations.
Since the names cpu_maps_update_begin/done() don't make much sense in CPU
hotplug callback registration scenarios, we'll introduce new APIs named
cpu_notifier_register_begin/done() and map them to cpu_maps_update_begin/done().
In summary, introduce the lockless variants of un/register_cpu_notifier() and
also export the cpu_notifier_register_begin/done() APIs for use by modules.
This way, we provide a race-free way to register hotplug callbacks as well as
perform initialization for the CPUs that are already online.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Toshi Kani <toshi.kani@hp.com>
Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
include/linux/cpu.h | 47 +++++++++++++++++++++++++++++++++++++++++++++++
kernel/cpu.c | 21 +++++++++++++++++++--
2 files changed, 66 insertions(+), 2 deletions(-)
diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 03e235ad..488d6eb 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -122,26 +122,46 @@ enum {
{ .notifier_call = fn, .priority = pri }; \
register_cpu_notifier(&fn##_nb); \
}
+
+#define __cpu_notifier(fn, pri) { \
+ static struct notifier_block fn##_nb = \
+ { .notifier_call = fn, .priority = pri }; \
+ __register_cpu_notifier(&fn##_nb); \
+}
#else /* #if defined(CONFIG_HOTPLUG_CPU) || !defined(MODULE) */
#define cpu_notifier(fn, pri) do { (void)(fn); } while (0)
+#define __cpu_notifier(fn, pri) do { (void)(fn); } while (0)
#endif /* #else #if defined(CONFIG_HOTPLUG_CPU) || !defined(MODULE) */
+
#ifdef CONFIG_HOTPLUG_CPU
extern int register_cpu_notifier(struct notifier_block *nb);
+extern int __register_cpu_notifier(struct notifier_block *nb);
extern void unregister_cpu_notifier(struct notifier_block *nb);
+extern void __unregister_cpu_notifier(struct notifier_block *nb);
#else
#ifndef MODULE
extern int register_cpu_notifier(struct notifier_block *nb);
+extern int __register_cpu_notifier(struct notifier_block *nb);
#else
static inline int register_cpu_notifier(struct notifier_block *nb)
{
return 0;
}
+
+static inline int __register_cpu_notifier(struct notifier_block *nb)
+{
+ return 0;
+}
#endif
static inline void unregister_cpu_notifier(struct notifier_block *nb)
{
}
+
+static inline void __unregister_cpu_notifier(struct notifier_block *nb)
+{
+}
#endif
int cpu_up(unsigned int cpu);
@@ -149,19 +169,32 @@ void notify_cpu_starting(unsigned int cpu);
extern void cpu_maps_update_begin(void);
extern void cpu_maps_update_done(void);
+#define cpu_notifier_register_begin cpu_maps_update_begin
+#define cpu_notifier_register_done cpu_maps_update_done
+
#else /* CONFIG_SMP */
#define cpu_notifier(fn, pri) do { (void)(fn); } while (0)
+#define __cpu_notifier(fn, pri) do { (void)(fn); } while (0)
static inline int register_cpu_notifier(struct notifier_block *nb)
{
return 0;
}
+static inline int __register_cpu_notifier(struct notifier_block *nb)
+{
+ return 0;
+}
+
static inline void unregister_cpu_notifier(struct notifier_block *nb)
{
}
+static inline void __unregister_cpu_notifier(struct notifier_block *nb)
+{
+}
+
static inline void cpu_maps_update_begin(void)
{
}
@@ -170,6 +203,14 @@ static inline void cpu_maps_update_done(void)
{
}
+static inline void cpu_notifier_register_begin(void)
+{
+}
+
+static inline void cpu_notifier_register_done(void)
+{
+}
+
#endif /* CONFIG_SMP */
extern struct bus_type cpu_subsys;
@@ -183,8 +224,11 @@ extern void put_online_cpus(void);
extern void cpu_hotplug_disable(void);
extern void cpu_hotplug_enable(void);
#define hotcpu_notifier(fn, pri) cpu_notifier(fn, pri)
+#define __hotcpu_notifier(fn, pri) __cpu_notifier(fn, pri)
#define register_hotcpu_notifier(nb) register_cpu_notifier(nb)
+#define __register_hotcpu_notifier(nb) __register_cpu_notifier(nb)
#define unregister_hotcpu_notifier(nb) unregister_cpu_notifier(nb)
+#define __unregister_hotcpu_notifier(nb) __unregister_cpu_notifier(nb)
void clear_tasks_mm_cpumask(int cpu);
int cpu_down(unsigned int cpu);
@@ -197,9 +241,12 @@ static inline void cpu_hotplug_done(void) {}
#define cpu_hotplug_disable() do { } while (0)
#define cpu_hotplug_enable() do { } while (0)
#define hotcpu_notifier(fn, pri) do { (void)(fn); } while (0)
+#define __hotcpu_notifier(fn, pri) do { (void)(fn); } while (0)
/* These aren't inline functions due to a GCC bug. */
#define register_hotcpu_notifier(nb) ({ (void)(nb); 0; })
+#define __register_hotcpu_notifier(nb) ({ (void)(nb); 0; })
#define unregister_hotcpu_notifier(nb) ({ (void)(nb); })
+#define __unregister_hotcpu_notifier(nb) ({ (void)(nb); })
#endif /* CONFIG_HOTPLUG_CPU */
#ifdef CONFIG_PM_SLEEP_SMP
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 33caf5e..a9e710e 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -28,18 +28,23 @@
static DEFINE_MUTEX(cpu_add_remove_lock);
/*
- * The following two API's must be used when attempting
- * to serialize the updates to cpu_online_mask, cpu_present_mask.
+ * The following two APIs (cpu_maps_update_begin/done) must be used when
+ * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
+ * The APIs cpu_notifier_register_begin/done() must be used to protect CPU
+ * hotplug callback (un)registration performed using __register_cpu_notifier()
+ * or __unregister_cpu_notifier().
*/
void cpu_maps_update_begin(void)
{
mutex_lock(&cpu_add_remove_lock);
}
+EXPORT_SYMBOL(cpu_notifier_register_begin);
void cpu_maps_update_done(void)
{
mutex_unlock(&cpu_add_remove_lock);
}
+EXPORT_SYMBOL(cpu_notifier_register_done);
static RAW_NOTIFIER_HEAD(cpu_chain);
@@ -183,6 +188,11 @@ int __ref register_cpu_notifier(struct notifier_block *nb)
return ret;
}
+int __ref __register_cpu_notifier(struct notifier_block *nb)
+{
+ return raw_notifier_chain_register(&cpu_chain, nb);
+}
+
static int __cpu_notify(unsigned long val, void *v, int nr_to_call,
int *nr_calls)
{
@@ -206,6 +216,7 @@ static void cpu_notify_nofail(unsigned long val, void *v)
BUG_ON(cpu_notify(val, v));
}
EXPORT_SYMBOL(register_cpu_notifier);
+EXPORT_SYMBOL(__register_cpu_notifier);
void __ref unregister_cpu_notifier(struct notifier_block *nb)
{
@@ -215,6 +226,12 @@ void __ref unregister_cpu_notifier(struct notifier_block *nb)
}
EXPORT_SYMBOL(unregister_cpu_notifier);
+void __ref __unregister_cpu_notifier(struct notifier_block *nb)
+{
+ raw_notifier_chain_unregister(&cpu_chain, nb);
+}
+EXPORT_SYMBOL(__unregister_cpu_notifier);
+
/**
* clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
* @cpu: a CPU id
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 03/52] Doc/cpu-hotplug: Specify race-free way to register CPU hotplug callbacks
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
2014-03-10 20:34 ` [PATCH v3 01/52] CPU hotplug: Add lockdep annotations to get/put_online_cpus() Srivatsa S. Bhat
2014-03-10 20:34 ` [PATCH v3 02/52] CPU hotplug: Provide lockless versions of callback registration functions Srivatsa S. Bhat
@ 2014-03-10 20:34 ` Srivatsa S. Bhat
2014-03-10 20:34 ` [PATCH v3 04/52] CPU hotplug, perf: Fix CPU hotplug callback registration Srivatsa S. Bhat
` (50 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:34 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, Rob Landley, linux-pm, linux-doc,
linux-kernel, linuxppc-dev, Srivatsa S. Bhat, tj, paulmck,
Ingo Molnar
Recommend the usage of the new CPU hotplug callback registration APIs
(__register_cpu_notifier() etc), when subsystems need to also perform
initialization for already online CPUs. Provide examples of correct
and race-free ways of achieving this, and point out the kinds of code
that are error-prone.
Cc: Rob Landley <rob@landley.net>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-doc@vger.kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
Documentation/cpu-hotplug.txt | 45 +++++++++++++++++++++++++++++++++++++++++
1 file changed, 45 insertions(+)
diff --git a/Documentation/cpu-hotplug.txt b/Documentation/cpu-hotplug.txt
index be675d2..a0b005d 100644
--- a/Documentation/cpu-hotplug.txt
+++ b/Documentation/cpu-hotplug.txt
@@ -312,12 +312,57 @@ things will happen if a notifier in path sent a BAD notify code.
Q: I don't see my action being called for all CPUs already up and running?
A: Yes, CPU notifiers are called only when new CPUs are on-lined or offlined.
If you need to perform some action for each cpu already in the system, then
+ do this:
for_each_online_cpu(i) {
foobar_cpu_callback(&foobar_cpu_notifier, CPU_UP_PREPARE, i);
foobar_cpu_callback(&foobar_cpu_notifier, CPU_ONLINE, i);
}
+ However, if you want to register a hotplug callback, as well as perform
+ some initialization for CPUs that are already online, then do this:
+
+ Version 1: (Correct)
+ ---------
+
+ cpu_notifier_register_begin();
+
+ for_each_online_cpu(i) {
+ foobar_cpu_callback(&foobar_cpu_notifier,
+ CPU_UP_PREPARE, i);
+ foobar_cpu_callback(&foobar_cpu_notifier,
+ CPU_ONLINE, i);
+ }
+
+ /* Note the use of the double underscored version of the API */
+ __register_cpu_notifier(&foobar_cpu_notifier);
+
+ cpu_notifier_register_done();
+
+ Note that the following code is *NOT* the right way to achieve this,
+ because it is prone to an ABBA deadlock between the cpu_add_remove_lock
+ and the cpu_hotplug.lock.
+
+ Version 2: (Wrong!)
+ ---------
+
+ get_online_cpus();
+
+ for_each_online_cpu(i) {
+ foobar_cpu_callback(&foobar_cpu_notifier,
+ CPU_UP_PREPARE, i);
+ foobar_cpu_callback(&foobar_cpu_notifier,
+ CPU_ONLINE, i);
+ }
+
+ register_cpu_notifier(&foobar_cpu_notifier);
+
+ put_online_cpus();
+
+ So always use the first version shown above when you want to register
+ callbacks as well as initialize the already online CPUs.
+
+
Q: If i would like to develop cpu hotplug support for a new architecture,
what do i need at a minimum?
A: The following are what is required for CPU hotplug infrastructure to work
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 04/52] CPU hotplug, perf: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (2 preceding siblings ...)
2014-03-10 20:34 ` [PATCH v3 03/52] Doc/cpu-hotplug: Specify race-free way to register CPU hotplug callbacks Srivatsa S. Bhat
@ 2014-03-10 20:34 ` Srivatsa S. Bhat
2014-03-10 20:34 ` [PATCH v3 05/52] ia64, salinfo: Fix " Srivatsa S. Bhat
` (49 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:34 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, Arnaldo Carvalho de Melo,
linux-pm, Peter Zijlstra, linux-kernel, linuxppc-dev,
Paul Mackerras, Srivatsa S. Bhat, tj, paulmck, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the perf subsystem's hotplug notifier by using this latter form of
callback registration.
Also provide a bare-bones version of perf_cpu_notifier() that doesn't
invoke the notifiers for the already online CPUs. This would be useful
for subsystems that need to perform a different set of initialization
for the already online CPUs, or don't need the initialization altogether.
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
include/linux/perf_event.h | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index e56b07f..3356abc 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -835,6 +835,8 @@ do { \
{ .notifier_call = fn, .priority = CPU_PRI_PERF }; \
unsigned long cpu = smp_processor_id(); \
unsigned long flags; \
+ \
+ cpu_notifier_register_begin(); \
fn(&fn##_nb, (unsigned long)CPU_UP_PREPARE, \
(void *)(unsigned long)cpu); \
local_irq_save(flags); \
@@ -843,9 +845,21 @@ do { \
local_irq_restore(flags); \
fn(&fn##_nb, (unsigned long)CPU_ONLINE, \
(void *)(unsigned long)cpu); \
- register_cpu_notifier(&fn##_nb); \
+ __register_cpu_notifier(&fn##_nb); \
+ cpu_notifier_register_done(); \
} while (0)
+/*
+ * Bare-bones version of perf_cpu_notifier(), which doesn't invoke the
+ * callback for already online CPUs.
+ */
+#define __perf_cpu_notifier(fn) \
+do { \
+ static struct notifier_block fn##_nb = \
+ { .notifier_call = fn, .priority = CPU_PRI_PERF }; \
+ \
+ __register_cpu_notifier(&fn##_nb); \
+} while (0)
struct perf_pmu_events_attr {
struct device_attribute attr;
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 05/52] ia64, salinfo: Fix hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (3 preceding siblings ...)
2014-03-10 20:34 ` [PATCH v3 04/52] CPU hotplug, perf: Fix CPU hotplug callback registration Srivatsa S. Bhat
@ 2014-03-10 20:34 ` Srivatsa S. Bhat
2014-03-10 20:34 ` [PATCH v3 06/52] ia64, palinfo: Fix CPU " Srivatsa S. Bhat
` (48 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:34 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, linux-kernel,
Fenghua Yu, linuxppc-dev, Tony Luck, Srivatsa S. Bhat, tj,
linux-ia64, paulmck, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the salinfo code in ia64 by using this latter form of callback
registration.
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-ia64@vger.kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
arch/ia64/kernel/salinfo.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/ia64/kernel/salinfo.c b/arch/ia64/kernel/salinfo.c
index 960a396..ee9719e 100644
--- a/arch/ia64/kernel/salinfo.c
+++ b/arch/ia64/kernel/salinfo.c
@@ -635,6 +635,8 @@ salinfo_init(void)
(void *)salinfo_entries[i].feature);
}
+ cpu_notifier_register_begin();
+
for (i = 0; i < ARRAY_SIZE(salinfo_log_name); i++) {
data = salinfo_data + i;
data->type = i;
@@ -669,7 +671,9 @@ salinfo_init(void)
salinfo_timer.function = &salinfo_timeout;
add_timer(&salinfo_timer);
- register_hotcpu_notifier(&salinfo_cpu_notifier);
+ __register_hotcpu_notifier(&salinfo_cpu_notifier);
+
+ cpu_notifier_register_done();
return 0;
}
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 06/52] ia64, palinfo: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (4 preceding siblings ...)
2014-03-10 20:34 ` [PATCH v3 05/52] ia64, salinfo: Fix " Srivatsa S. Bhat
@ 2014-03-10 20:34 ` Srivatsa S. Bhat
2014-03-10 20:34 ` [PATCH v3 07/52] ia64, topology: " Srivatsa S. Bhat
` (47 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:34 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, linux-kernel,
Fenghua Yu, linuxppc-dev, Tony Luck, Srivatsa S. Bhat, tj,
linux-ia64, paulmck, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the palinfo code in ia64 by using this latter form of callback
registration.
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-ia64@vger.kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
arch/ia64/kernel/palinfo.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/ia64/kernel/palinfo.c b/arch/ia64/kernel/palinfo.c
index ab33328..c39c3cd 100644
--- a/arch/ia64/kernel/palinfo.c
+++ b/arch/ia64/kernel/palinfo.c
@@ -996,13 +996,17 @@ palinfo_init(void)
if (!palinfo_dir)
return -ENOMEM;
+ cpu_notifier_register_begin();
+
/* Create palinfo dirs in /proc for all online cpus */
for_each_online_cpu(i) {
create_palinfo_proc_entries(i);
}
/* Register for future delivery via notify registration */
- register_hotcpu_notifier(&palinfo_cpu_notifier);
+ __register_hotcpu_notifier(&palinfo_cpu_notifier);
+
+ cpu_notifier_register_done();
return 0;
}
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 07/52] ia64, topology: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (5 preceding siblings ...)
2014-03-10 20:34 ` [PATCH v3 06/52] ia64, palinfo: Fix CPU " Srivatsa S. Bhat
@ 2014-03-10 20:34 ` Srivatsa S. Bhat
2014-03-10 20:35 ` [PATCH v3 08/52] ia64, err-inject: " Srivatsa S. Bhat
` (46 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:34 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, linux-kernel,
Fenghua Yu, linuxppc-dev, Tony Luck, Srivatsa S. Bhat, tj,
linux-ia64, paulmck, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the topology code in ia64 by using this latter form of callback
registration.
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-ia64@vger.kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
arch/ia64/kernel/topology.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/ia64/kernel/topology.c b/arch/ia64/kernel/topology.c
index ca69a5a..f295f9a 100644
--- a/arch/ia64/kernel/topology.c
+++ b/arch/ia64/kernel/topology.c
@@ -454,12 +454,16 @@ static int __init cache_sysfs_init(void)
{
int i;
+ cpu_notifier_register_begin();
+
for_each_online_cpu(i) {
struct device *sys_dev = get_cpu_device((unsigned int)i);
cache_add_dev(sys_dev);
}
- register_hotcpu_notifier(&cache_cpu_notifier);
+ __register_hotcpu_notifier(&cache_cpu_notifier);
+
+ cpu_notifier_register_done();
return 0;
}
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 08/52] ia64, err-inject: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (6 preceding siblings ...)
2014-03-10 20:34 ` [PATCH v3 07/52] ia64, topology: " Srivatsa S. Bhat
@ 2014-03-10 20:35 ` Srivatsa S. Bhat
2014-03-10 20:35 ` [PATCH v3 09/52] arm, hw-breakpoint: " Srivatsa S. Bhat
` (45 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:35 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, linux-kernel,
Fenghua Yu, linuxppc-dev, Tony Luck, Srivatsa S. Bhat, tj,
linux-ia64, paulmck, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the error injection code in ia64 by using this latter form of callback
registration.
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-ia64@vger.kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
arch/ia64/kernel/err_inject.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
diff --git a/arch/ia64/kernel/err_inject.c b/arch/ia64/kernel/err_inject.c
index f59c0b8..0c161ed 100644
--- a/arch/ia64/kernel/err_inject.c
+++ b/arch/ia64/kernel/err_inject.c
@@ -269,12 +269,17 @@ err_inject_init(void)
#ifdef ERR_INJ_DEBUG
printk(KERN_INFO "Enter error injection driver.\n");
#endif
+
+ cpu_notifier_register_begin();
+
for_each_online_cpu(i) {
err_inject_cpu_callback(&err_inject_cpu_notifier, CPU_ONLINE,
(void *)(long)i);
}
- register_hotcpu_notifier(&err_inject_cpu_notifier);
+ __register_hotcpu_notifier(&err_inject_cpu_notifier);
+
+ cpu_notifier_register_done();
return 0;
}
@@ -288,11 +293,17 @@ err_inject_exit(void)
#ifdef ERR_INJ_DEBUG
printk(KERN_INFO "Exit error injection driver.\n");
#endif
+
+ cpu_notifier_register_begin();
+
for_each_online_cpu(i) {
sys_dev = get_cpu_device(i);
sysfs_remove_group(&sys_dev->kobj, &err_inject_attr_group);
}
- unregister_hotcpu_notifier(&err_inject_cpu_notifier);
+
+ __unregister_hotcpu_notifier(&err_inject_cpu_notifier);
+
+ cpu_notifier_register_done();
}
module_init(err_inject_init);
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 09/52] arm, hw-breakpoint: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (7 preceding siblings ...)
2014-03-10 20:35 ` [PATCH v3 08/52] ia64, err-inject: " Srivatsa S. Bhat
@ 2014-03-10 20:35 ` Srivatsa S. Bhat
2014-03-10 20:35 ` [PATCH v3 10/52] arm, kvm: " Srivatsa S. Bhat
` (44 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:35 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, Russell King, linux-pm, Will Deacon,
linux-kernel, linuxppc-dev, Srivatsa S. Bhat, tj, paulmck,
Ingo Molnar, linux-arm-kernel
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the hw-breakpoint code in arm by using this latter form of callback
registration.
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
arch/arm/kernel/hw_breakpoint.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c
index 3d44660..3702de8 100644
--- a/arch/arm/kernel/hw_breakpoint.c
+++ b/arch/arm/kernel/hw_breakpoint.c
@@ -1072,6 +1072,8 @@ static int __init arch_hw_breakpoint_init(void)
core_num_brps = get_num_brps();
core_num_wrps = get_num_wrps();
+ cpu_notifier_register_begin();
+
/*
* We need to tread carefully here because DBGSWENABLE may be
* driven low on this core and there isn't an architected way to
@@ -1088,6 +1090,7 @@ static int __init arch_hw_breakpoint_init(void)
if (!cpumask_empty(&debug_err_mask)) {
core_num_brps = 0;
core_num_wrps = 0;
+ cpu_notifier_register_done();
return 0;
}
@@ -1107,7 +1110,10 @@ static int __init arch_hw_breakpoint_init(void)
TRAP_HWBKPT, "breakpoint debug exception");
/* Register hotplug and PM notifiers. */
- register_cpu_notifier(&dbg_reset_nb);
+ __register_cpu_notifier(&dbg_reset_nb);
+
+ cpu_notifier_register_done();
+
pm_init();
return 0;
}
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 10/52] arm, kvm: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (8 preceding siblings ...)
2014-03-10 20:35 ` [PATCH v3 09/52] arm, hw-breakpoint: " Srivatsa S. Bhat
@ 2014-03-10 20:35 ` Srivatsa S. Bhat
2014-03-12 23:21 ` Christoffer Dall
2014-03-10 20:35 ` [PATCH v3 11/52] s390, cacheinfo: " Srivatsa S. Bhat
` (43 subsequent siblings)
53 siblings, 1 reply; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:35 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, Russell King, kvm, linux-pm,
Gleb Natapov, linux-kernel, kvmarm, linuxppc-dev,
linux-arm-kernel, Srivatsa S. Bhat, tj, Paolo Bonzini, paulmck,
Ingo Molnar, Christoffer Dall
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the kvm code in arm by using this latter form of callback registration.
Cc: Christoffer Dall <christoffer.dall@linaro.org>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: kvmarm@lists.cs.columbia.edu
Cc: kvm@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
arch/arm/kvm/arm.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index bd18bb8..f0e50a0 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -1051,21 +1051,26 @@ int kvm_arch_init(void *opaque)
}
}
+ cpu_notifier_register_begin();
+
err = init_hyp_mode();
if (err)
goto out_err;
- err = register_cpu_notifier(&hyp_init_cpu_nb);
+ err = __register_cpu_notifier(&hyp_init_cpu_nb);
if (err) {
kvm_err("Cannot register HYP init CPU notifier (%d)\n", err);
goto out_err;
}
+ cpu_notifier_register_done();
+
hyp_cpu_pm_init();
kvm_coproc_table_init();
return 0;
out_err:
+ cpu_notifier_register_done();
return err;
}
^ permalink raw reply related [flat|nested] 63+ messages in thread* Re: [PATCH v3 10/52] arm, kvm: Fix CPU hotplug callback registration
2014-03-10 20:35 ` [PATCH v3 10/52] arm, kvm: " Srivatsa S. Bhat
@ 2014-03-12 23:21 ` Christoffer Dall
2014-03-14 5:43 ` Srivatsa S. Bhat
0 siblings, 1 reply; 63+ messages in thread
From: Christoffer Dall @ 2014-03-12 23:21 UTC (permalink / raw)
To: Srivatsa S. Bhat
Cc: ego, kvm, peterz, linux-kernel, linuxppc-dev, paulus, walken,
kvmarm, linux-arch, linux, mingo, marc.zyngier, paulmck,
linux-pm, Gleb Natapov, rusty, tglx, linux-arm-kernel, rjw, oleg,
tj, Paolo Bonzini, akpm
On Tue, Mar 11, 2014 at 02:05:38AM +0530, Srivatsa S. Bhat wrote:
> Subsystems that want to register CPU hotplug callbacks, as well as perform
> initialization for the CPUs that are already online, often do it as shown
> below:
>
> get_online_cpus();
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> register_cpu_notifier(&foobar_cpu_notifier);
>
> put_online_cpus();
>
> This is wrong, since it is prone to ABBA deadlocks involving the
> cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
> with CPU hotplug operations).
>
> Instead, the correct and race-free way of performing the callback
> registration is:
>
> cpu_notifier_register_begin();
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> /* Note the use of the double underscored version of the API */
> __register_cpu_notifier(&foobar_cpu_notifier);
>
> cpu_notifier_register_done();
>
>
> Fix the kvm code in arm by using this latter form of callback registration.
>
> Cc: Christoffer Dall <christoffer.dall@linaro.org>
> Cc: Gleb Natapov <gleb@kernel.org>
> Cc: Russell King <linux@arm.linux.org.uk>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: kvmarm@lists.cs.columbia.edu
> Cc: kvm@vger.kernel.org
> Cc: linux-arm-kernel@lists.infradead.org
> Acked-by: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
> ---
>
> arch/arm/kvm/arm.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index bd18bb8..f0e50a0 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -1051,21 +1051,26 @@ int kvm_arch_init(void *opaque)
> }
> }
>
> + cpu_notifier_register_begin();
> +
> err = init_hyp_mode();
> if (err)
> goto out_err;
>
> - err = register_cpu_notifier(&hyp_init_cpu_nb);
> + err = __register_cpu_notifier(&hyp_init_cpu_nb);
> if (err) {
> kvm_err("Cannot register HYP init CPU notifier (%d)\n", err);
> goto out_err;
> }
>
> + cpu_notifier_register_done();
> +
> hyp_cpu_pm_init();
>
> kvm_coproc_table_init();
> return 0;
> out_err:
> + cpu_notifier_register_done();
> return err;
> }
>
>
Just so we're clear, the existing code was simply racy as not prone to
deadlocks, right?
This makes it clear that the test above for compatible CPUs can be quite
easily evaded by using CPU hotplug, but we don't really have a good
solution for handling that yet... Hmmm, grumble grumble, I guess if you
hotplug unsupported CPUs on a KVM/ARM system for now, stuff will break.
In any case:
Acked-by: Christoffer Dall <christoffer.dall@linaro.org>
^ permalink raw reply [flat|nested] 63+ messages in thread* Re: [PATCH v3 10/52] arm, kvm: Fix CPU hotplug callback registration
2014-03-12 23:21 ` Christoffer Dall
@ 2014-03-14 5:43 ` Srivatsa S. Bhat
2014-03-14 19:10 ` Christoffer Dall
0 siblings, 1 reply; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-14 5:43 UTC (permalink / raw)
To: Christoffer Dall
Cc: ego, kvm, peterz, linux-kernel, linuxppc-dev, paulus, walken,
kvmarm, linux-arch, linux, mingo, marc.zyngier, paulmck,
linux-pm, Gleb Natapov, rusty, tglx, linux-arm-kernel, rjw, oleg,
tj, Paolo Bonzini, akpm
On 03/13/2014 04:51 AM, Christoffer Dall wrote:
> On Tue, Mar 11, 2014 at 02:05:38AM +0530, Srivatsa S. Bhat wrote:
>> Subsystems that want to register CPU hotplug callbacks, as well as perform
>> initialization for the CPUs that are already online, often do it as shown
>> below:
>>
>> get_online_cpus();
>>
>> for_each_online_cpu(cpu)
>> init_cpu(cpu);
>>
>> register_cpu_notifier(&foobar_cpu_notifier);
>>
>> put_online_cpus();
>>
>> This is wrong, since it is prone to ABBA deadlocks involving the
>> cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
>> with CPU hotplug operations).
>>
>> Instead, the correct and race-free way of performing the callback
>> registration is:
>>
>> cpu_notifier_register_begin();
>>
>> for_each_online_cpu(cpu)
>> init_cpu(cpu);
>>
>> /* Note the use of the double underscored version of the API */
>> __register_cpu_notifier(&foobar_cpu_notifier);
>>
>> cpu_notifier_register_done();
>>
>>
>> Fix the kvm code in arm by using this latter form of callback registration.
>>
>> Cc: Christoffer Dall <christoffer.dall@linaro.org>
>> Cc: Gleb Natapov <gleb@kernel.org>
>> Cc: Russell King <linux@arm.linux.org.uk>
>> Cc: Ingo Molnar <mingo@kernel.org>
>> Cc: kvmarm@lists.cs.columbia.edu
>> Cc: kvm@vger.kernel.org
>> Cc: linux-arm-kernel@lists.infradead.org
>> Acked-by: Paolo Bonzini <pbonzini@redhat.com>
>> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
>> ---
>>
>> arch/arm/kvm/arm.c | 7 ++++++-
>> 1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
>> index bd18bb8..f0e50a0 100644
>> --- a/arch/arm/kvm/arm.c
>> +++ b/arch/arm/kvm/arm.c
>> @@ -1051,21 +1051,26 @@ int kvm_arch_init(void *opaque)
>> }
>> }
>>
>> + cpu_notifier_register_begin();
>> +
>> err = init_hyp_mode();
>> if (err)
>> goto out_err;
>>
>> - err = register_cpu_notifier(&hyp_init_cpu_nb);
>> + err = __register_cpu_notifier(&hyp_init_cpu_nb);
>> if (err) {
>> kvm_err("Cannot register HYP init CPU notifier (%d)\n", err);
>> goto out_err;
>> }
>>
>> + cpu_notifier_register_done();
>> +
>> hyp_cpu_pm_init();
>>
>> kvm_coproc_table_init();
>> return 0;
>> out_err:
>> + cpu_notifier_register_done();
>> return err;
>> }
>>
>>
>
> Just so we're clear, the existing code was simply racy as not prone to
> deadlocks, right?
>
> This makes it clear that the test above for compatible CPUs can be quite
> easily evaded by using CPU hotplug, but we don't really have a good
> solution for handling that yet... Hmmm, grumble grumble, I guess if you
> hotplug unsupported CPUs on a KVM/ARM system for now, stuff will break.
>
In this particular case, there was no deadlock possibility, rather the
existing code had insufficient synchronization against CPU hotplug.
init_hyp_mode() would invoke cpu_init_hyp_mode() on currently online CPUs
using on_each_cpu(). If a CPU came online after this point and before calling
register_cpu_notifier(), that CPU would remain uninitialized because this
subsystem would miss the hot-online event. This patch fixes this bug and
also uses the new synchronization method (instead of get/put_online_cpus())
to ensure that we don't deadlock with CPU hotplug.
> In any case:
> Acked-by: Christoffer Dall <christoffer.dall@linaro.org>
>
Thanks a lot!
Regards,
Srivatsa S. Bhat
^ permalink raw reply [flat|nested] 63+ messages in thread* Re: [PATCH v3 10/52] arm, kvm: Fix CPU hotplug callback registration
2014-03-14 5:43 ` Srivatsa S. Bhat
@ 2014-03-14 19:10 ` Christoffer Dall
2014-03-18 10:23 ` [UPDATED PATCH " Srivatsa S. Bhat
0 siblings, 1 reply; 63+ messages in thread
From: Christoffer Dall @ 2014-03-14 19:10 UTC (permalink / raw)
To: Srivatsa S. Bhat
Cc: ego, kvm, peterz, linux-kernel, linuxppc-dev, paulus, walken,
kvmarm, linux-arch, linux, mingo, marc.zyngier, paulmck,
linux-pm, Gleb Natapov, rusty, tglx, linux-arm-kernel, rjw, oleg,
tj, Paolo Bonzini, akpm
On Fri, Mar 14, 2014 at 11:13:29AM +0530, Srivatsa S. Bhat wrote:
> On 03/13/2014 04:51 AM, Christoffer Dall wrote:
> > On Tue, Mar 11, 2014 at 02:05:38AM +0530, Srivatsa S. Bhat wrote:
> >> Subsystems that want to register CPU hotplug callbacks, as well as perform
> >> initialization for the CPUs that are already online, often do it as shown
> >> below:
> >>
> >> get_online_cpus();
> >>
> >> for_each_online_cpu(cpu)
> >> init_cpu(cpu);
> >>
> >> register_cpu_notifier(&foobar_cpu_notifier);
> >>
> >> put_online_cpus();
> >>
> >> This is wrong, since it is prone to ABBA deadlocks involving the
> >> cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
> >> with CPU hotplug operations).
> >>
> >> Instead, the correct and race-free way of performing the callback
> >> registration is:
> >>
> >> cpu_notifier_register_begin();
> >>
> >> for_each_online_cpu(cpu)
> >> init_cpu(cpu);
> >>
> >> /* Note the use of the double underscored version of the API */
> >> __register_cpu_notifier(&foobar_cpu_notifier);
> >>
> >> cpu_notifier_register_done();
> >>
> >>
> >> Fix the kvm code in arm by using this latter form of callback registration.
> >>
> >> Cc: Christoffer Dall <christoffer.dall@linaro.org>
> >> Cc: Gleb Natapov <gleb@kernel.org>
> >> Cc: Russell King <linux@arm.linux.org.uk>
> >> Cc: Ingo Molnar <mingo@kernel.org>
> >> Cc: kvmarm@lists.cs.columbia.edu
> >> Cc: kvm@vger.kernel.org
> >> Cc: linux-arm-kernel@lists.infradead.org
> >> Acked-by: Paolo Bonzini <pbonzini@redhat.com>
> >> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
> >> ---
> >>
> >> arch/arm/kvm/arm.c | 7 ++++++-
> >> 1 file changed, 6 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> >> index bd18bb8..f0e50a0 100644
> >> --- a/arch/arm/kvm/arm.c
> >> +++ b/arch/arm/kvm/arm.c
> >> @@ -1051,21 +1051,26 @@ int kvm_arch_init(void *opaque)
> >> }
> >> }
> >>
> >> + cpu_notifier_register_begin();
> >> +
> >> err = init_hyp_mode();
> >> if (err)
> >> goto out_err;
> >>
> >> - err = register_cpu_notifier(&hyp_init_cpu_nb);
> >> + err = __register_cpu_notifier(&hyp_init_cpu_nb);
> >> if (err) {
> >> kvm_err("Cannot register HYP init CPU notifier (%d)\n", err);
> >> goto out_err;
> >> }
> >>
> >> + cpu_notifier_register_done();
> >> +
> >> hyp_cpu_pm_init();
> >>
> >> kvm_coproc_table_init();
> >> return 0;
> >> out_err:
> >> + cpu_notifier_register_done();
> >> return err;
> >> }
> >>
> >>
> >
> > Just so we're clear, the existing code was simply racy as not prone to
> > deadlocks, right?
> >
> > This makes it clear that the test above for compatible CPUs can be quite
> > easily evaded by using CPU hotplug, but we don't really have a good
> > solution for handling that yet... Hmmm, grumble grumble, I guess if you
> > hotplug unsupported CPUs on a KVM/ARM system for now, stuff will break.
> >
>
> In this particular case, there was no deadlock possibility, rather the
> existing code had insufficient synchronization against CPU hotplug.
>
> init_hyp_mode() would invoke cpu_init_hyp_mode() on currently online CPUs
> using on_each_cpu(). If a CPU came online after this point and before calling
> register_cpu_notifier(), that CPU would remain uninitialized because this
> subsystem would miss the hot-online event. This patch fixes this bug and
> also uses the new synchronization method (instead of get/put_online_cpus())
> to ensure that we don't deadlock with CPU hotplug.
>
Yes, that was my conclusion as well. Thanks for clarifying. (It could
be noted in the commit message as well if you should feel so inclined).
> > In any case:
> > Acked-by: Christoffer Dall <christoffer.dall@linaro.org>
> >
>
> Thanks a lot!
>
Thanks,
-Christoffer
^ permalink raw reply [flat|nested] 63+ messages in thread* [UPDATED PATCH v3 10/52] arm, kvm: Fix CPU hotplug callback registration
2014-03-14 19:10 ` Christoffer Dall
@ 2014-03-18 10:23 ` Srivatsa S. Bhat
2014-03-18 22:08 ` Christoffer Dall
0 siblings, 1 reply; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-18 10:23 UTC (permalink / raw)
To: Christoffer Dall
Cc: ego, kvm, peterz, oleg, linuxppc-dev, paulus, walken, mingo,
linux-arch, linux, kvmarm, Gleb Natapov, paulmck, linux-pm,
marc.zyngier, rusty, tglx, linux-arm-kernel, rjw, linux-kernel,
tj, Paolo Bonzini, akpm
On 03/15/2014 12:40 AM, Christoffer Dall wrote:
> On Fri, Mar 14, 2014 at 11:13:29AM +0530, Srivatsa S. Bhat wrote:
>> On 03/13/2014 04:51 AM, Christoffer Dall wrote:
>>> On Tue, Mar 11, 2014 at 02:05:38AM +0530, Srivatsa S. Bhat wrote:
>>>> Subsystems that want to register CPU hotplug callbacks, as well as perform
>>>> initialization for the CPUs that are already online, often do it as shown
>>>> below:
>>>>
[...]
>>> Just so we're clear, the existing code was simply racy as not prone to
>>> deadlocks, right?
>>>
>>> This makes it clear that the test above for compatible CPUs can be quite
>>> easily evaded by using CPU hotplug, but we don't really have a good
>>> solution for handling that yet... Hmmm, grumble grumble, I guess if you
>>> hotplug unsupported CPUs on a KVM/ARM system for now, stuff will break.
>>>
>>
>> In this particular case, there was no deadlock possibility, rather the
>> existing code had insufficient synchronization against CPU hotplug.
>>
>> init_hyp_mode() would invoke cpu_init_hyp_mode() on currently online CPUs
>> using on_each_cpu(). If a CPU came online after this point and before calling
>> register_cpu_notifier(), that CPU would remain uninitialized because this
>> subsystem would miss the hot-online event. This patch fixes this bug and
>> also uses the new synchronization method (instead of get/put_online_cpus())
>> to ensure that we don't deadlock with CPU hotplug.
>>
>
> Yes, that was my conclusion as well. Thanks for clarifying. (It could
> be noted in the commit message as well if you should feel so inclined).
>
Please find the patch with updated changelog (and your Ack) below.
(No changes in code).
From: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Subject: [PATCH] arm, kvm: Fix CPU hotplug callback registration
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
In the existing arm kvm code, there is no synchronization with CPU hotplug
to avoid missing the hotplug events that might occur after invoking
init_hyp_mode() and before calling register_cpu_notifier(). Fix this bug
and also use the new synchronization method (instead of get/put_online_cpus())
to ensure that we don't deadlock with CPU hotplug.
Cc: Gleb Natapov <gleb@kernel.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: kvmarm@lists.cs.columbia.edu
Cc: kvm@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
arch/arm/kvm/arm.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index bd18bb8..f0e50a0 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -1051,21 +1051,26 @@ int kvm_arch_init(void *opaque)
}
}
+ cpu_notifier_register_begin();
+
err = init_hyp_mode();
if (err)
goto out_err;
- err = register_cpu_notifier(&hyp_init_cpu_nb);
+ err = __register_cpu_notifier(&hyp_init_cpu_nb);
if (err) {
kvm_err("Cannot register HYP init CPU notifier (%d)\n", err);
goto out_err;
}
+ cpu_notifier_register_done();
+
hyp_cpu_pm_init();
kvm_coproc_table_init();
return 0;
out_err:
+ cpu_notifier_register_done();
return err;
}
^ permalink raw reply related [flat|nested] 63+ messages in thread* Re: [UPDATED PATCH v3 10/52] arm, kvm: Fix CPU hotplug callback registration
2014-03-18 10:23 ` [UPDATED PATCH " Srivatsa S. Bhat
@ 2014-03-18 22:08 ` Christoffer Dall
0 siblings, 0 replies; 63+ messages in thread
From: Christoffer Dall @ 2014-03-18 22:08 UTC (permalink / raw)
To: Srivatsa S. Bhat
Cc: ego, kvm, peterz, oleg, linuxppc-dev, Paul Mackerras,
Michel Lespinasse, mingo, linux-arch, Russell King, kvmarm,
Gleb Natapov, Paul McKenney, linux-pm, Marc Zyngier,
Rusty Russell, Thomas Gleixner, linux-arm-kernel, rjw,
linux-kernel, tj, Paolo Bonzini, akpm
On 18 March 2014 03:23, Srivatsa S. Bhat
<srivatsa.bhat@linux.vnet.ibm.com> wrote:
> On 03/15/2014 12:40 AM, Christoffer Dall wrote:
>> On Fri, Mar 14, 2014 at 11:13:29AM +0530, Srivatsa S. Bhat wrote:
>>> On 03/13/2014 04:51 AM, Christoffer Dall wrote:
>>>> On Tue, Mar 11, 2014 at 02:05:38AM +0530, Srivatsa S. Bhat wrote:
>>>>> Subsystems that want to register CPU hotplug callbacks, as well as perform
>>>>> initialization for the CPUs that are already online, often do it as shown
>>>>> below:
>>>>>
> [...]
>>>> Just so we're clear, the existing code was simply racy as not prone to
>>>> deadlocks, right?
>>>>
>>>> This makes it clear that the test above for compatible CPUs can be quite
>>>> easily evaded by using CPU hotplug, but we don't really have a good
>>>> solution for handling that yet... Hmmm, grumble grumble, I guess if you
>>>> hotplug unsupported CPUs on a KVM/ARM system for now, stuff will break.
>>>>
>>>
>>> In this particular case, there was no deadlock possibility, rather the
>>> existing code had insufficient synchronization against CPU hotplug.
>>>
>>> init_hyp_mode() would invoke cpu_init_hyp_mode() on currently online CPUs
>>> using on_each_cpu(). If a CPU came online after this point and before calling
>>> register_cpu_notifier(), that CPU would remain uninitialized because this
>>> subsystem would miss the hot-online event. This patch fixes this bug and
>>> also uses the new synchronization method (instead of get/put_online_cpus())
>>> to ensure that we don't deadlock with CPU hotplug.
>>>
>>
>> Yes, that was my conclusion as well. Thanks for clarifying. (It could
>> be noted in the commit message as well if you should feel so inclined).
>>
>
> Please find the patch with updated changelog (and your Ack) below.
> (No changes in code).
>
perfect, thanks!
> From: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
> Subject: [PATCH] arm, kvm: Fix CPU hotplug callback registration
>
> Subsystems that want to register CPU hotplug callbacks, as well as perform
> initialization for the CPUs that are already online, often do it as shown
> below:
>
> get_online_cpus();
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> register_cpu_notifier(&foobar_cpu_notifier);
>
> put_online_cpus();
>
> This is wrong, since it is prone to ABBA deadlocks involving the
> cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
> with CPU hotplug operations).
>
> Instead, the correct and race-free way of performing the callback
> registration is:
>
> cpu_notifier_register_begin();
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> /* Note the use of the double underscored version of the API */
> __register_cpu_notifier(&foobar_cpu_notifier);
>
> cpu_notifier_register_done();
>
>
> In the existing arm kvm code, there is no synchronization with CPU hotplug
> to avoid missing the hotplug events that might occur after invoking
> init_hyp_mode() and before calling register_cpu_notifier(). Fix this bug
> and also use the new synchronization method (instead of get/put_online_cpus())
> to ensure that we don't deadlock with CPU hotplug.
>
> Cc: Gleb Natapov <gleb@kernel.org>
> Cc: Russell King <linux@arm.linux.org.uk>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: kvmarm@lists.cs.columbia.edu
> Cc: kvm@vger.kernel.org
> Cc: linux-arm-kernel@lists.infradead.org
> Acked-by: Paolo Bonzini <pbonzini@redhat.com>
> Acked-by: Christoffer Dall <christoffer.dall@linaro.org>
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
> ---
>
> arch/arm/kvm/arm.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index bd18bb8..f0e50a0 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -1051,21 +1051,26 @@ int kvm_arch_init(void *opaque)
> }
> }
>
> + cpu_notifier_register_begin();
> +
> err = init_hyp_mode();
> if (err)
> goto out_err;
>
> - err = register_cpu_notifier(&hyp_init_cpu_nb);
> + err = __register_cpu_notifier(&hyp_init_cpu_nb);
> if (err) {
> kvm_err("Cannot register HYP init CPU notifier (%d)\n", err);
> goto out_err;
> }
>
> + cpu_notifier_register_done();
> +
> hyp_cpu_pm_init();
>
> kvm_coproc_table_init();
> return 0;
> out_err:
> + cpu_notifier_register_done();
> return err;
> }
>
>
>
^ permalink raw reply [flat|nested] 63+ messages in thread
* [PATCH v3 11/52] s390, cacheinfo: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (9 preceding siblings ...)
2014-03-10 20:35 ` [PATCH v3 10/52] arm, kvm: " Srivatsa S. Bhat
@ 2014-03-10 20:35 ` Srivatsa S. Bhat
2014-03-10 20:35 ` [PATCH v3 12/52] s390, smp: " Srivatsa S. Bhat
` (42 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:35 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, linux-s390,
Heiko Carstens, linux-kernel, Ingo Molnar, linuxppc-dev,
Srivatsa S. Bhat, tj, paulmck, Martin Schwidefsky
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the cacheinfo code in s390 by using this latter form of callback
registration.
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-s390@vger.kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
arch/s390/kernel/cache.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/s390/kernel/cache.c b/arch/s390/kernel/cache.c
index 3a414c0..c0b03c2 100644
--- a/arch/s390/kernel/cache.c
+++ b/arch/s390/kernel/cache.c
@@ -378,9 +378,12 @@ static int __init cache_init(void)
if (!test_facility(34))
return 0;
cache_build_info();
+
+ cpu_notifier_register_begin();
for_each_online_cpu(cpu)
cache_add_cpu(cpu);
- hotcpu_notifier(cache_hotplug, 0);
+ __hotcpu_notifier(cache_hotplug, 0);
+ cpu_notifier_register_done();
return 0;
}
device_initcall(cache_init);
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 12/52] s390, smp: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (10 preceding siblings ...)
2014-03-10 20:35 ` [PATCH v3 11/52] s390, cacheinfo: " Srivatsa S. Bhat
@ 2014-03-10 20:35 ` Srivatsa S. Bhat
2014-03-10 20:36 ` [PATCH v3 13/52] sparc, sysfs: " Srivatsa S. Bhat
` (41 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:35 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, linux-s390,
Heiko Carstens, linux-kernel, Ingo Molnar, linuxppc-dev,
Srivatsa S. Bhat, tj, Thomas Gleixner, paulmck,
Martin Schwidefsky
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the smp code in s390 by using this latter form of callback registration.
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-s390@vger.kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
arch/s390/kernel/smp.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index a7125b6..e10be35 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -1057,19 +1057,24 @@ static DEVICE_ATTR(rescan, 0200, NULL, rescan_store);
static int __init s390_smp_init(void)
{
- int cpu, rc;
+ int cpu, rc = 0;
- hotcpu_notifier(smp_cpu_notify, 0);
#ifdef CONFIG_HOTPLUG_CPU
rc = device_create_file(cpu_subsys.dev_root, &dev_attr_rescan);
if (rc)
return rc;
#endif
+ cpu_notifier_register_begin();
for_each_present_cpu(cpu) {
rc = smp_add_present_cpu(cpu);
if (rc)
- return rc;
+ goto out;
}
- return 0;
+
+ __hotcpu_notifier(smp_cpu_notify, 0);
+
+out:
+ cpu_notifier_register_done();
+ return rc;
}
subsys_initcall(s390_smp_init);
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 13/52] sparc, sysfs: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (11 preceding siblings ...)
2014-03-10 20:35 ` [PATCH v3 12/52] s390, smp: " Srivatsa S. Bhat
@ 2014-03-10 20:36 ` Srivatsa S. Bhat
2014-03-10 20:36 ` [PATCH v3 14/52] powerpc, " Srivatsa S. Bhat
` (40 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:36 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, sparclinux, walken, linux, linux-pm,
linux-kernel, David S. Miller, linuxppc-dev, Srivatsa S. Bhat,
tj, paulmck, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the sysfs code in sparc by using this latter form of callback
registration.
Cc: Ingo Molnar <mingo@kernel.org>
Cc: sparclinux@vger.kernel.org
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
arch/sparc/kernel/sysfs.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/sparc/kernel/sysfs.c b/arch/sparc/kernel/sysfs.c
index c21c673..a364000 100644
--- a/arch/sparc/kernel/sysfs.c
+++ b/arch/sparc/kernel/sysfs.c
@@ -300,7 +300,7 @@ static int __init topology_init(void)
check_mmu_stats();
- register_cpu_notifier(&sysfs_cpu_nb);
+ cpu_notifier_register_begin();
for_each_possible_cpu(cpu) {
struct cpu *c = &per_cpu(cpu_devices, cpu);
@@ -310,6 +310,10 @@ static int __init topology_init(void)
register_cpu_online(cpu);
}
+ __register_cpu_notifier(&sysfs_cpu_nb);
+
+ cpu_notifier_register_done();
+
return 0;
}
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 14/52] powerpc, sysfs: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (12 preceding siblings ...)
2014-03-10 20:36 ` [PATCH v3 13/52] sparc, sysfs: " Srivatsa S. Bhat
@ 2014-03-10 20:36 ` Srivatsa S. Bhat
2014-03-10 20:36 ` [PATCH v3 15/52] x86, msr: " Srivatsa S. Bhat
` (39 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:36 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, Olof Johansson,
linux-kernel, Wang Dongsheng, linuxppc-dev, Madhavan Srinivasan,
Paul Mackerras, Srivatsa S. Bhat, tj, paulmck, linuxppc-dev,
Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the sysfs code in powerpc by using this latter form of callback
registration.
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Olof Johansson <olof@lixom.net>
Cc: Wang Dongsheng <dongsheng.wang@freescale.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linuxppc-dev@lists.ozlabs.org
Acked-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
arch/powerpc/kernel/sysfs.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c
index 97e1dc9..d90d4b7 100644
--- a/arch/powerpc/kernel/sysfs.c
+++ b/arch/powerpc/kernel/sysfs.c
@@ -975,7 +975,8 @@ static int __init topology_init(void)
int cpu;
register_nodes();
- register_cpu_notifier(&sysfs_cpu_nb);
+
+ cpu_notifier_register_begin();
for_each_possible_cpu(cpu) {
struct cpu *c = &per_cpu(cpu_devices, cpu);
@@ -999,6 +1000,11 @@ static int __init topology_init(void)
if (cpu_online(cpu))
register_cpu_online(cpu);
}
+
+ __register_cpu_notifier(&sysfs_cpu_nb);
+
+ cpu_notifier_register_done();
+
#ifdef CONFIG_PPC64
sysfs_create_dscr_default();
#endif /* CONFIG_PPC64 */
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 15/52] x86, msr: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (13 preceding siblings ...)
2014-03-10 20:36 ` [PATCH v3 14/52] powerpc, " Srivatsa S. Bhat
@ 2014-03-10 20:36 ` Srivatsa S. Bhat
2014-03-10 20:36 ` [PATCH v3 16/52] x86, cpuid: " Srivatsa S. Bhat
` (38 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:36 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, x86, linux-kernel,
linuxppc-dev, Srivatsa S. Bhat, H. Peter Anvin, tj,
Thomas Gleixner, paulmck, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the msr code in x86 by using this latter form of callback registration.
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: x86@kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
arch/x86/kernel/msr.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c
index 05266b5..c9603ac 100644
--- a/arch/x86/kernel/msr.c
+++ b/arch/x86/kernel/msr.c
@@ -259,14 +259,15 @@ static int __init msr_init(void)
goto out_chrdev;
}
msr_class->devnode = msr_devnode;
- get_online_cpus();
+
+ cpu_notifier_register_begin();
for_each_online_cpu(i) {
err = msr_device_create(i);
if (err != 0)
goto out_class;
}
- register_hotcpu_notifier(&msr_class_cpu_notifier);
- put_online_cpus();
+ __register_hotcpu_notifier(&msr_class_cpu_notifier);
+ cpu_notifier_register_done();
err = 0;
goto out;
@@ -275,7 +276,7 @@ out_class:
i = 0;
for_each_online_cpu(i)
msr_device_destroy(i);
- put_online_cpus();
+ cpu_notifier_register_done();
class_destroy(msr_class);
out_chrdev:
__unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
@@ -286,13 +287,14 @@ out:
static void __exit msr_exit(void)
{
int cpu = 0;
- get_online_cpus();
+
+ cpu_notifier_register_begin();
for_each_online_cpu(cpu)
msr_device_destroy(cpu);
class_destroy(msr_class);
__unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
- unregister_hotcpu_notifier(&msr_class_cpu_notifier);
- put_online_cpus();
+ __unregister_hotcpu_notifier(&msr_class_cpu_notifier);
+ cpu_notifier_register_done();
}
module_init(msr_init);
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 16/52] x86, cpuid: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (14 preceding siblings ...)
2014-03-10 20:36 ` [PATCH v3 15/52] x86, msr: " Srivatsa S. Bhat
@ 2014-03-10 20:36 ` Srivatsa S. Bhat
2014-03-10 20:36 ` [PATCH v3 17/52] x86, vsyscall: " Srivatsa S. Bhat
` (37 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:36 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, x86, linux-kernel,
linuxppc-dev, Srivatsa S. Bhat, H. Peter Anvin, tj,
Thomas Gleixner, paulmck, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the cpuid code in x86 by using this latter form of callback registration.
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: x86@kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
arch/x86/kernel/cpuid.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kernel/cpuid.c b/arch/x86/kernel/cpuid.c
index 7d9481c..3225ae6c 100644
--- a/arch/x86/kernel/cpuid.c
+++ b/arch/x86/kernel/cpuid.c
@@ -198,14 +198,15 @@ static int __init cpuid_init(void)
goto out_chrdev;
}
cpuid_class->devnode = cpuid_devnode;
- get_online_cpus();
+
+ cpu_notifier_register_begin();
for_each_online_cpu(i) {
err = cpuid_device_create(i);
if (err != 0)
goto out_class;
}
- register_hotcpu_notifier(&cpuid_class_cpu_notifier);
- put_online_cpus();
+ __register_hotcpu_notifier(&cpuid_class_cpu_notifier);
+ cpu_notifier_register_done();
err = 0;
goto out;
@@ -215,7 +216,7 @@ out_class:
for_each_online_cpu(i) {
cpuid_device_destroy(i);
}
- put_online_cpus();
+ cpu_notifier_register_done();
class_destroy(cpuid_class);
out_chrdev:
__unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
@@ -227,13 +228,13 @@ static void __exit cpuid_exit(void)
{
int cpu = 0;
- get_online_cpus();
+ cpu_notifier_register_begin();
for_each_online_cpu(cpu)
cpuid_device_destroy(cpu);
class_destroy(cpuid_class);
__unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
- unregister_hotcpu_notifier(&cpuid_class_cpu_notifier);
- put_online_cpus();
+ __unregister_hotcpu_notifier(&cpuid_class_cpu_notifier);
+ cpu_notifier_register_done();
}
module_init(cpuid_init);
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 17/52] x86, vsyscall: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (15 preceding siblings ...)
2014-03-10 20:36 ` [PATCH v3 16/52] x86, cpuid: " Srivatsa S. Bhat
@ 2014-03-10 20:36 ` Srivatsa S. Bhat
2014-03-10 20:36 ` [PATCH v3 18/52] x86, intel, uncore: " Srivatsa S. Bhat
` (36 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:36 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, x86, linux-kernel,
linuxppc-dev, Srivatsa S. Bhat, H. Peter Anvin, tj,
Thomas Gleixner, paulmck, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the vsyscall code in x86 by using this latter form of callback
registration.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
arch/x86/kernel/vsyscall_64.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c
index 1f96f93..556eaf2 100644
--- a/arch/x86/kernel/vsyscall_64.c
+++ b/arch/x86/kernel/vsyscall_64.c
@@ -393,9 +393,13 @@ static int __init vsyscall_init(void)
{
BUG_ON(VSYSCALL_ADDR(0) != __fix_to_virt(VSYSCALL_FIRST_PAGE));
+ cpu_notifier_register_begin();
+
on_each_cpu(cpu_vsyscall_init, NULL, 1);
/* notifier priority > KVM */
- hotcpu_notifier(cpu_vsyscall_notifier, 30);
+ __hotcpu_notifier(cpu_vsyscall_notifier, 30);
+
+ cpu_notifier_register_done();
return 0;
}
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 18/52] x86, intel, uncore: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (16 preceding siblings ...)
2014-03-10 20:36 ` [PATCH v3 17/52] x86, vsyscall: " Srivatsa S. Bhat
@ 2014-03-10 20:36 ` Srivatsa S. Bhat
2014-03-10 20:37 ` [PATCH v3 19/52] x86, mce: " Srivatsa S. Bhat
` (35 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:36 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, Arnaldo Carvalho de Melo,
linux-pm, Peter Zijlstra, x86, linux-kernel, linuxppc-dev,
Paul Mackerras, Srivatsa S. Bhat, H. Peter Anvin, tj,
Thomas Gleixner, paulmck, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the uncore code in intel-x86 by using this latter form of callback
registration.
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
arch/x86/kernel/cpu/perf_event_intel_uncore.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event_intel_uncore.c b/arch/x86/kernel/cpu/perf_event_intel_uncore.c
index c88f7f4..e90183d 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_uncore.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_uncore.c
@@ -3816,7 +3816,7 @@ static int __init uncore_cpu_init(void)
if (ret)
return ret;
- get_online_cpus();
+ cpu_notifier_register_begin();
for_each_online_cpu(cpu) {
int i, phys_id = topology_physical_package_id(cpu);
@@ -3835,9 +3835,9 @@ static int __init uncore_cpu_init(void)
}
on_each_cpu(uncore_cpu_setup, NULL, 1);
- register_cpu_notifier(&uncore_cpu_nb);
+ __register_cpu_notifier(&uncore_cpu_nb);
- put_online_cpus();
+ cpu_notifier_register_done();
return 0;
}
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 19/52] x86, mce: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (17 preceding siblings ...)
2014-03-10 20:36 ` [PATCH v3 18/52] x86, intel, uncore: " Srivatsa S. Bhat
@ 2014-03-10 20:37 ` Srivatsa S. Bhat
2014-03-10 20:37 ` [PATCH v3 20/52] x86, therm_throt.c: " Srivatsa S. Bhat
` (34 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:37 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, x86, linux-kernel,
linuxppc-dev, Tony Luck, Borislav Petkov, Srivatsa S. Bhat,
H. Peter Anvin, tj, Thomas Gleixner, paulmck, Ingo Molnar,
linux-edac
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the mce code in x86 by using this latter form of callback registration.
Cc: Tony Luck <tony.luck@intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: linux-edac@vger.kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
arch/x86/kernel/cpu/mcheck/mce.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 4d5419b..9b7734b 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -2434,14 +2434,18 @@ static __init int mcheck_init_device(void)
if (err)
return err;
+ cpu_notifier_register_begin();
for_each_online_cpu(i) {
err = mce_device_create(i);
- if (err)
+ if (err) {
+ cpu_notifier_register_done();
return err;
+ }
}
register_syscore_ops(&mce_syscore_ops);
- register_hotcpu_notifier(&mce_cpu_notifier);
+ __register_hotcpu_notifier(&mce_cpu_notifier);
+ cpu_notifier_register_done();
/* register character device /dev/mcelog */
misc_register(&mce_chrdev_device);
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 20/52] x86, therm_throt.c: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (18 preceding siblings ...)
2014-03-10 20:37 ` [PATCH v3 19/52] x86, mce: " Srivatsa S. Bhat
@ 2014-03-10 20:37 ` Srivatsa S. Bhat
2014-03-10 20:37 ` [PATCH v3 21/52] x86, therm_throt.c: Remove unused therm_cpu_lock Srivatsa S. Bhat
` (33 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:37 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, x86, linux-kernel,
linuxppc-dev, Tony Luck, Borislav Petkov, Srivatsa S. Bhat,
H. Peter Anvin, tj, Thomas Gleixner, paulmck, Ingo Molnar,
linux-edac
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the thermal throttle code in x86 by using this latter form of callback
registration.
Cc: Tony Luck <tony.luck@intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: linux-edac@vger.kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
arch/x86/kernel/cpu/mcheck/therm_throt.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/cpu/mcheck/therm_throt.c b/arch/x86/kernel/cpu/mcheck/therm_throt.c
index 3eec7de..e05dfa3 100644
--- a/arch/x86/kernel/cpu/mcheck/therm_throt.c
+++ b/arch/x86/kernel/cpu/mcheck/therm_throt.c
@@ -319,7 +319,7 @@ static __init int thermal_throttle_init_device(void)
if (!atomic_read(&therm_throt_en))
return 0;
- register_hotcpu_notifier(&thermal_throttle_cpu_notifier);
+ cpu_notifier_register_begin();
#ifdef CONFIG_HOTPLUG_CPU
mutex_lock(&therm_cpu_lock);
@@ -333,6 +333,9 @@ static __init int thermal_throttle_init_device(void)
mutex_unlock(&therm_cpu_lock);
#endif
+ __register_hotcpu_notifier(&thermal_throttle_cpu_notifier);
+ cpu_notifier_register_done();
+
return 0;
}
device_initcall(thermal_throttle_init_device);
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 21/52] x86, therm_throt.c: Remove unused therm_cpu_lock
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (19 preceding siblings ...)
2014-03-10 20:37 ` [PATCH v3 20/52] x86, therm_throt.c: " Srivatsa S. Bhat
@ 2014-03-10 20:37 ` Srivatsa S. Bhat
2014-03-10 20:37 ` [PATCH v3 22/52] x86, amd, ibs: Fix CPU hotplug callback registration Srivatsa S. Bhat
` (32 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:37 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, x86, linux-kernel,
linuxppc-dev, Tony Luck, Borislav Petkov, Srivatsa S. Bhat,
H. Peter Anvin, tj, Thomas Gleixner, paulmck, Ingo Molnar,
linux-edac
After fixing the CPU hotplug callback registration code, the callbacks
invoked for each online CPU, during the initialization phase in
thermal_throttle_init_device(), can no longer race with the actual CPU
hotplug notifier callbacks (in thermal_throttle_cpu_callback). Hence the
therm_cpu_lock is unnecessary now. Remove it.
Cc: Tony Luck <tony.luck@intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: linux-edac@vger.kernel.org
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
arch/x86/kernel/cpu/mcheck/therm_throt.c | 13 -------------
1 file changed, 13 deletions(-)
diff --git a/arch/x86/kernel/cpu/mcheck/therm_throt.c b/arch/x86/kernel/cpu/mcheck/therm_throt.c
index e05dfa3..d921b7e 100644
--- a/arch/x86/kernel/cpu/mcheck/therm_throt.c
+++ b/arch/x86/kernel/cpu/mcheck/therm_throt.c
@@ -271,9 +271,6 @@ static void thermal_throttle_remove_dev(struct device *dev)
sysfs_remove_group(&dev->kobj, &thermal_attr_group);
}
-/* Mutex protecting device creation against CPU hotplug: */
-static DEFINE_MUTEX(therm_cpu_lock);
-
/* Get notified when a cpu comes on/off. Be hotplug friendly. */
static int
thermal_throttle_cpu_callback(struct notifier_block *nfb,
@@ -289,18 +286,14 @@ thermal_throttle_cpu_callback(struct notifier_block *nfb,
switch (action) {
case CPU_UP_PREPARE:
case CPU_UP_PREPARE_FROZEN:
- mutex_lock(&therm_cpu_lock);
err = thermal_throttle_add_dev(dev, cpu);
- mutex_unlock(&therm_cpu_lock);
WARN_ON(err);
break;
case CPU_UP_CANCELED:
case CPU_UP_CANCELED_FROZEN:
case CPU_DEAD:
case CPU_DEAD_FROZEN:
- mutex_lock(&therm_cpu_lock);
thermal_throttle_remove_dev(dev);
- mutex_unlock(&therm_cpu_lock);
break;
}
return notifier_from_errno(err);
@@ -321,17 +314,11 @@ static __init int thermal_throttle_init_device(void)
cpu_notifier_register_begin();
-#ifdef CONFIG_HOTPLUG_CPU
- mutex_lock(&therm_cpu_lock);
-#endif
/* connect live CPUs to sysfs */
for_each_online_cpu(cpu) {
err = thermal_throttle_add_dev(get_cpu_device(cpu), cpu);
WARN_ON(err);
}
-#ifdef CONFIG_HOTPLUG_CPU
- mutex_unlock(&therm_cpu_lock);
-#endif
__register_hotcpu_notifier(&thermal_throttle_cpu_notifier);
cpu_notifier_register_done();
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 22/52] x86, amd, ibs: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (20 preceding siblings ...)
2014-03-10 20:37 ` [PATCH v3 21/52] x86, therm_throt.c: Remove unused therm_cpu_lock Srivatsa S. Bhat
@ 2014-03-10 20:37 ` Srivatsa S. Bhat
2014-03-10 20:37 ` [PATCH v3 23/52] x86, intel, cacheinfo: " Srivatsa S. Bhat
` (31 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:37 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, Arnaldo Carvalho de Melo,
linux-pm, Peter Zijlstra, x86, linux-kernel, linuxppc-dev,
Paul Mackerras, Srivatsa S. Bhat, H. Peter Anvin, tj,
Thomas Gleixner, paulmck, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the amd-ibs code in x86 by using this latter form of callback
registration.
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
arch/x86/kernel/cpu/perf_event_amd_ibs.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event_amd_ibs.c b/arch/x86/kernel/cpu/perf_event_amd_ibs.c
index 4b8e4d3..4c36bbe 100644
--- a/arch/x86/kernel/cpu/perf_event_amd_ibs.c
+++ b/arch/x86/kernel/cpu/perf_event_amd_ibs.c
@@ -926,13 +926,13 @@ static __init int amd_ibs_init(void)
goto out;
perf_ibs_pm_init();
- get_online_cpus();
+ cpu_notifier_register_begin();
ibs_caps = caps;
/* make ibs_caps visible to other cpus: */
smp_mb();
- perf_cpu_notifier(perf_ibs_cpu_notifier);
smp_call_function(setup_APIC_ibs, NULL, 1);
- put_online_cpus();
+ __perf_cpu_notifier(perf_ibs_cpu_notifier);
+ cpu_notifier_register_done();
ret = perf_event_ibs_init();
out:
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 23/52] x86, intel, cacheinfo: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (21 preceding siblings ...)
2014-03-10 20:37 ` [PATCH v3 22/52] x86, amd, ibs: Fix CPU hotplug callback registration Srivatsa S. Bhat
@ 2014-03-10 20:37 ` Srivatsa S. Bhat
2014-03-10 20:38 ` [PATCH v3 24/52] x86, intel, rapl: " Srivatsa S. Bhat
` (30 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:37 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, x86, linux-kernel,
linuxppc-dev, Borislav Petkov, Srivatsa S. Bhat, H. Peter Anvin,
tj, Thomas Gleixner, paulmck, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the intel cacheinfo code in x86 by using this latter form of callback
registration.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: Borislav Petkov <bp@suse.de>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
arch/x86/kernel/cpu/intel_cacheinfo.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kernel/cpu/intel_cacheinfo.c b/arch/x86/kernel/cpu/intel_cacheinfo.c
index 0641113..a952e9c 100644
--- a/arch/x86/kernel/cpu/intel_cacheinfo.c
+++ b/arch/x86/kernel/cpu/intel_cacheinfo.c
@@ -1225,21 +1225,24 @@ static struct notifier_block cacheinfo_cpu_notifier = {
static int __init cache_sysfs_init(void)
{
- int i;
+ int i, err = 0;
if (num_cache_leaves == 0)
return 0;
+ cpu_notifier_register_begin();
for_each_online_cpu(i) {
- int err;
struct device *dev = get_cpu_device(i);
err = cache_add_dev(dev);
if (err)
- return err;
+ goto out;
}
- register_hotcpu_notifier(&cacheinfo_cpu_notifier);
- return 0;
+ __register_hotcpu_notifier(&cacheinfo_cpu_notifier);
+
+out:
+ cpu_notifier_register_done();
+ return err;
}
device_initcall(cache_sysfs_init);
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 24/52] x86, intel, rapl: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (22 preceding siblings ...)
2014-03-10 20:37 ` [PATCH v3 23/52] x86, intel, cacheinfo: " Srivatsa S. Bhat
@ 2014-03-10 20:38 ` Srivatsa S. Bhat
2014-03-10 20:38 ` [PATCH v3 25/52] x86, amd, uncore: " Srivatsa S. Bhat
` (29 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:38 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, Arnaldo Carvalho de Melo,
linux-pm, Peter Zijlstra, x86, linux-kernel, linuxppc-dev,
Paul Mackerras, Srivatsa S. Bhat, H. Peter Anvin, tj,
Thomas Gleixner, paulmck, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the intel rapl code in x86 by using this latter form of callback
registration.
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
arch/x86/kernel/cpu/perf_event_intel_rapl.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event_intel_rapl.c b/arch/x86/kernel/cpu/perf_event_intel_rapl.c
index 5ad35ad..059218e 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_rapl.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_rapl.c
@@ -646,19 +646,20 @@ static int __init rapl_pmu_init(void)
/* unsupported */
return 0;
}
- get_online_cpus();
+
+ cpu_notifier_register_begin();
for_each_online_cpu(cpu) {
rapl_cpu_prepare(cpu);
rapl_cpu_init(cpu);
}
- perf_cpu_notifier(rapl_cpu_notifier);
+ __perf_cpu_notifier(rapl_cpu_notifier);
ret = perf_pmu_register(&rapl_pmu_class, "power", -1);
if (WARN_ON(ret)) {
pr_info("RAPL PMU detected, registration failed (%d), RAPL PMU disabled\n", ret);
- put_online_cpus();
+ cpu_notifier_register_done();
return -1;
}
@@ -672,7 +673,7 @@ static int __init rapl_pmu_init(void)
hweight32(rapl_cntr_mask),
ktime_to_ms(pmu->timer_interval));
- put_online_cpus();
+ cpu_notifier_register_done();
return 0;
}
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 25/52] x86, amd, uncore: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (23 preceding siblings ...)
2014-03-10 20:38 ` [PATCH v3 24/52] x86, intel, rapl: " Srivatsa S. Bhat
@ 2014-03-10 20:38 ` Srivatsa S. Bhat
2014-03-10 20:38 ` [PATCH v3 26/52] x86, hpet: " Srivatsa S. Bhat
` (28 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:38 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, Arnaldo Carvalho de Melo,
linux-pm, Peter Zijlstra, x86, linux-kernel, linuxppc-dev,
Paul Mackerras, Srivatsa S. Bhat, H. Peter Anvin, tj,
Thomas Gleixner, paulmck, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the amd-uncore code in x86 by using this latter form of callback
registration.
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
arch/x86/kernel/cpu/perf_event_amd_uncore.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event_amd_uncore.c b/arch/x86/kernel/cpu/perf_event_amd_uncore.c
index 754291a..3bbdf4c 100644
--- a/arch/x86/kernel/cpu/perf_event_amd_uncore.c
+++ b/arch/x86/kernel/cpu/perf_event_amd_uncore.c
@@ -531,15 +531,16 @@ static int __init amd_uncore_init(void)
if (ret)
return -ENODEV;
- get_online_cpus();
+ cpu_notifier_register_begin();
+
/* init cpus already online before registering for hotplug notifier */
for_each_online_cpu(cpu) {
amd_uncore_cpu_up_prepare(cpu);
smp_call_function_single(cpu, init_cpu_already_online, NULL, 1);
}
- register_cpu_notifier(&amd_uncore_cpu_notifier_block);
- put_online_cpus();
+ __register_cpu_notifier(&amd_uncore_cpu_notifier_block);
+ cpu_notifier_register_done();
return 0;
}
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 26/52] x86, hpet: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (24 preceding siblings ...)
2014-03-10 20:38 ` [PATCH v3 25/52] x86, amd, uncore: " Srivatsa S. Bhat
@ 2014-03-10 20:38 ` Srivatsa S. Bhat
2014-03-10 20:38 ` [PATCH v3 27/52] x86, pci, amd-bus: " Srivatsa S. Bhat
` (27 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:38 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, x86, linux-kernel,
linuxppc-dev, Srivatsa S. Bhat, H. Peter Anvin, tj,
Thomas Gleixner, paulmck, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the hpet code in x86 by using this latter form of callback registration.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
arch/x86/kernel/hpet.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
index da85a8e..d89382b 100644
--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -943,12 +943,14 @@ static __init int hpet_late_init(void)
if (boot_cpu_has(X86_FEATURE_ARAT))
return 0;
+ cpu_notifier_register_begin();
for_each_online_cpu(cpu) {
hpet_cpuhp_notify(NULL, CPU_ONLINE, (void *)(long)cpu);
}
/* This notifier should be called after workqueue is ready */
- hotcpu_notifier(hpet_cpuhp_notify, -20);
+ __hotcpu_notifier(hpet_cpuhp_notify, -20);
+ cpu_notifier_register_done();
return 0;
}
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 27/52] x86, pci, amd-bus: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (25 preceding siblings ...)
2014-03-10 20:38 ` [PATCH v3 26/52] x86, hpet: " Srivatsa S. Bhat
@ 2014-03-10 20:38 ` Srivatsa S. Bhat
2014-03-10 20:38 ` [PATCH v3 28/52] x86, oprofile, nmi: " Srivatsa S. Bhat
` (26 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:38 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, linux-pci, x86,
linux-kernel, linuxppc-dev, Srivatsa S. Bhat, H. Peter Anvin, tj,
Thomas Gleixner, paulmck, Bjorn Helgaas, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the amd-bus code in x86 by using this latter form of callback
registration.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: linux-pci@vger.kernel.org
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
arch/x86/pci/amd_bus.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/x86/pci/amd_bus.c b/arch/x86/pci/amd_bus.c
index a48be98..f05cbf0 100644
--- a/arch/x86/pci/amd_bus.c
+++ b/arch/x86/pci/amd_bus.c
@@ -380,10 +380,13 @@ static int __init pci_io_ecs_init(void)
if (early_pci_allowed())
pci_enable_pci_io_ecs();
- register_cpu_notifier(&amd_cpu_notifier);
+ cpu_notifier_register_begin();
for_each_online_cpu(cpu)
amd_cpu_notify(&amd_cpu_notifier, (unsigned long)CPU_ONLINE,
(void *)(long)cpu);
+ __register_cpu_notifier(&amd_cpu_notifier);
+ cpu_notifier_register_done();
+
pci_probe |= PCI_HAS_IO_ECS;
return 0;
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 28/52] x86, oprofile, nmi: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (26 preceding siblings ...)
2014-03-10 20:38 ` [PATCH v3 27/52] x86, pci, amd-bus: " Srivatsa S. Bhat
@ 2014-03-10 20:38 ` Srivatsa S. Bhat
2014-03-10 20:39 ` [PATCH v3 29/52] x86, kvm: " Srivatsa S. Bhat
` (25 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:38 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, x86, linux-kernel,
linuxppc-dev, Srivatsa S. Bhat, H. Peter Anvin, tj,
Robert Richter, Thomas Gleixner, paulmck, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the oprofile code in x86 by using this latter form of callback
registration. But retain the calls to get/put_online_cpus(), since they are
used in other places as well, to protect the variables 'nmi_enabled' and
'ctr_running'. Strictly speaking, this is not necessary since
cpu_notifier_register_begin/done() provide a stronger synchronization
with CPU hotplug than get/put_online_cpus(). However, let's retain the
calls to get/put_online_cpus() to be consistent with the other call-sites.
By nesting get/put_online_cpus() *inside* cpu_notifier_register_begin/done(),
we avoid the ABBA deadlock possibility mentioned above.
Cc: Robert Richter <rric@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
arch/x86/oprofile/nmi_int.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
diff --git a/arch/x86/oprofile/nmi_int.c b/arch/x86/oprofile/nmi_int.c
index 6890d84..379e8bd 100644
--- a/arch/x86/oprofile/nmi_int.c
+++ b/arch/x86/oprofile/nmi_int.c
@@ -494,14 +494,19 @@ static int nmi_setup(void)
if (err)
goto fail;
+ cpu_notifier_register_begin();
+
+ /* Use get/put_online_cpus() to protect 'nmi_enabled' */
get_online_cpus();
- register_cpu_notifier(&oprofile_cpu_nb);
nmi_enabled = 1;
/* make nmi_enabled visible to the nmi handler: */
smp_mb();
on_each_cpu(nmi_cpu_setup, NULL, 1);
+ __register_cpu_notifier(&oprofile_cpu_nb);
put_online_cpus();
+ cpu_notifier_register_done();
+
return 0;
fail:
free_msrs();
@@ -512,12 +517,18 @@ static void nmi_shutdown(void)
{
struct op_msrs *msrs;
+ cpu_notifier_register_begin();
+
+ /* Use get/put_online_cpus() to protect 'nmi_enabled' & 'ctr_running' */
get_online_cpus();
- unregister_cpu_notifier(&oprofile_cpu_nb);
on_each_cpu(nmi_cpu_shutdown, NULL, 1);
nmi_enabled = 0;
ctr_running = 0;
+ __unregister_cpu_notifier(&oprofile_cpu_nb);
put_online_cpus();
+
+ cpu_notifier_register_done();
+
/* make variables visible to the nmi handler: */
smp_mb();
unregister_nmi_handler(NMI_LOCAL, "oprofile");
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 29/52] x86, kvm: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (27 preceding siblings ...)
2014-03-10 20:38 ` [PATCH v3 28/52] x86, oprofile, nmi: " Srivatsa S. Bhat
@ 2014-03-10 20:39 ` Srivatsa S. Bhat
2014-03-10 20:39 ` [PATCH v3 30/52] arm64, hw_breakpoint.c: " Srivatsa S. Bhat
` (24 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:39 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, kvm, linux-pm, Gleb Natapov, x86,
linux-kernel, linuxppc-dev, Srivatsa S. Bhat, H. Peter Anvin, tj,
Paolo Bonzini, Thomas Gleixner, paulmck, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the kvm code in x86 by using this latter form of callback registration.
Cc: Gleb Natapov <gleb@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: kvm@vger.kernel.org
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
arch/x86/kvm/x86.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2b85784..4db6f56 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5365,7 +5365,8 @@ static void kvm_timer_init(void)
int cpu;
max_tsc_khz = tsc_khz;
- register_hotcpu_notifier(&kvmclock_cpu_notifier_block);
+
+ cpu_notifier_register_begin();
if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) {
#ifdef CONFIG_CPU_FREQ
struct cpufreq_policy policy;
@@ -5382,6 +5383,10 @@ static void kvm_timer_init(void)
pr_debug("kvm: max_tsc_khz = %ld\n", max_tsc_khz);
for_each_online_cpu(cpu)
smp_call_function_single(cpu, tsc_khz_changed, NULL, 1);
+
+ __register_hotcpu_notifier(&kvmclock_cpu_notifier_block);
+ cpu_notifier_register_done();
+
}
static DEFINE_PER_CPU(struct kvm_vcpu *, current_vcpu);
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 30/52] arm64, hw_breakpoint.c: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (28 preceding siblings ...)
2014-03-10 20:39 ` [PATCH v3 29/52] x86, kvm: " Srivatsa S. Bhat
@ 2014-03-10 20:39 ` Srivatsa S. Bhat
2014-03-10 20:39 ` [PATCH v3 31/52] arm64, debug-monitors: " Srivatsa S. Bhat
` (23 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:39 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, Catalin Marinas,
Will Deacon, linux-kernel, linuxppc-dev, Lorenzo Pieralisi,
Srivatsa S. Bhat, tj, paulmck, Ingo Molnar, linux-arm-kernel
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the hw-breakpoint code in arm64 by using this latter form of callback
registration.
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Lorenzo Pieralisi <Lorenzo.Pieralisi@arm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
arch/arm64/kernel/hw_breakpoint.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_breakpoint.c
index f17f581..bee7897 100644
--- a/arch/arm64/kernel/hw_breakpoint.c
+++ b/arch/arm64/kernel/hw_breakpoint.c
@@ -913,6 +913,8 @@ static int __init arch_hw_breakpoint_init(void)
pr_info("found %d breakpoint and %d watchpoint registers.\n",
core_num_brps, core_num_wrps);
+ cpu_notifier_register_begin();
+
/*
* Reset the breakpoint resources. We assume that a halting
* debugger will leave the world in a nice state for us.
@@ -927,7 +929,10 @@ static int __init arch_hw_breakpoint_init(void)
TRAP_HWBKPT, "hw-watchpoint handler");
/* Register hotplug notifier. */
- register_cpu_notifier(&hw_breakpoint_reset_nb);
+ __register_cpu_notifier(&hw_breakpoint_reset_nb);
+
+ cpu_notifier_register_done();
+
/* Register cpu_suspend hw breakpoint restore hook */
cpu_suspend_set_dbg_restorer(hw_breakpoint_reset);
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 31/52] arm64, debug-monitors: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (29 preceding siblings ...)
2014-03-10 20:39 ` [PATCH v3 30/52] arm64, hw_breakpoint.c: " Srivatsa S. Bhat
@ 2014-03-10 20:39 ` Srivatsa S. Bhat
2014-03-10 20:39 ` [PATCH v3 32/52] powercap, intel-rapl: " Srivatsa S. Bhat
` (22 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:39 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, Catalin Marinas,
Will Deacon, linux-kernel, linuxppc-dev, Srivatsa S. Bhat, tj,
Russell King, paulmck, Ingo Molnar, linux-arm-kernel
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the debug-monitors code in arm64 by using this latter form of callback
registration.
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
arch/arm64/kernel/debug-monitors.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c
index 636ba8b..c985531 100644
--- a/arch/arm64/kernel/debug-monitors.c
+++ b/arch/arm64/kernel/debug-monitors.c
@@ -155,12 +155,16 @@ static struct notifier_block os_lock_nb = {
static int debug_monitors_init(void)
{
+ cpu_notifier_register_begin();
+
/* Clear the OS lock. */
smp_call_function(clear_os_lock, NULL, 1);
clear_os_lock(NULL);
/* Register hotplug handler. */
- register_cpu_notifier(&os_lock_nb);
+ __register_cpu_notifier(&os_lock_nb);
+
+ cpu_notifier_register_done();
return 0;
}
postcore_initcall(debug_monitors_init);
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 32/52] powercap, intel-rapl: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (30 preceding siblings ...)
2014-03-10 20:39 ` [PATCH v3 31/52] arm64, debug-monitors: " Srivatsa S. Bhat
@ 2014-03-10 20:39 ` Srivatsa S. Bhat
2014-03-12 22:27 ` Jacob Pan
2014-03-10 20:39 ` [PATCH v3 33/52] scsi, bnx2i: " Srivatsa S. Bhat
` (21 subsequent siblings)
53 siblings, 1 reply; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:39 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, Rafael J. Wysocki,
linux-kernel, linuxppc-dev, Jacob Pan, Srivatsa S. Bhat,
Srinivas Pandruvada, tj, paulmck, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the intel-rapl code in the powercap driver by using this latter form
of callback registration. But retain the calls to get/put_online_cpus(),
since they also protect the function rapl_cleanup_data(). By nesting
get/put_online_cpus() *inside* cpu_notifier_register_begin/done(), we avoid
the ABBA deadlock possibility mentioned above.
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
drivers/powercap/intel_rapl.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/powercap/intel_rapl.c b/drivers/powercap/intel_rapl.c
index 3c67683..d6c74c1 100644
--- a/drivers/powercap/intel_rapl.c
+++ b/drivers/powercap/intel_rapl.c
@@ -1369,6 +1369,9 @@ static int __init rapl_init(void)
return -ENODEV;
}
+
+ cpu_notifier_register_begin();
+
/* prevent CPU hotplug during detection */
get_online_cpus();
ret = rapl_detect_topology();
@@ -1380,20 +1383,23 @@ static int __init rapl_init(void)
ret = -ENODEV;
goto done;
}
- register_hotcpu_notifier(&rapl_cpu_notifier);
+ __register_hotcpu_notifier(&rapl_cpu_notifier);
done:
put_online_cpus();
+ cpu_notifier_register_done();
return ret;
}
static void __exit rapl_exit(void)
{
+ cpu_notifier_register_begin();
get_online_cpus();
- unregister_hotcpu_notifier(&rapl_cpu_notifier);
+ __unregister_hotcpu_notifier(&rapl_cpu_notifier);
rapl_unregister_powercap();
rapl_cleanup_data();
put_online_cpus();
+ cpu_notifier_register_done();
}
module_init(rapl_init);
^ permalink raw reply related [flat|nested] 63+ messages in thread* Re: [PATCH v3 32/52] powercap, intel-rapl: Fix CPU hotplug callback registration
2014-03-10 20:39 ` [PATCH v3 32/52] powercap, intel-rapl: " Srivatsa S. Bhat
@ 2014-03-12 22:27 ` Jacob Pan
0 siblings, 0 replies; 63+ messages in thread
From: Jacob Pan @ 2014-03-12 22:27 UTC (permalink / raw)
To: Srivatsa S. Bhat
Cc: linux-arch, ego, walken, linux, akpm, linux-pm, peterz, rusty,
rjw, oleg, linux-kernel, linuxppc-dev, paulus,
Srinivas Pandruvada, tj, tglx, paulmck, mingo
On Tue, 11 Mar 2014 02:09:26 +0530
"Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com> wrote:
> Subsystems that want to register CPU hotplug callbacks, as well as
> perform initialization for the CPUs that are already online, often do
> it as shown below:
>
> get_online_cpus();
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> register_cpu_notifier(&foobar_cpu_notifier);
>
> put_online_cpus();
>
> This is wrong, since it is prone to ABBA deadlocks involving the
> cpu_add_remove_lock and the cpu_hotplug.lock (when running
> concurrently with CPU hotplug operations).
>
> Instead, the correct and race-free way of performing the callback
> registration is:
>
> cpu_notifier_register_begin();
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> /* Note the use of the double underscored version of the API
> */ __register_cpu_notifier(&foobar_cpu_notifier);
>
> cpu_notifier_register_done();
>
>
> Fix the intel-rapl code in the powercap driver by using this latter
> form of callback registration. But retain the calls to
> get/put_online_cpus(), since they also protect the function
> rapl_cleanup_data(). By nesting get/put_online_cpus() *inside*
> cpu_notifier_register_begin/done(), we avoid the ABBA deadlock
> possibility mentioned above.
>
> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
> Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
> Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
> Cc: Ingo Molnar <mingo@kernel.org>
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
> ---
>
Tested-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> drivers/powercap/intel_rapl.c | 10 ++++++++--
> 1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/powercap/intel_rapl.c
> b/drivers/powercap/intel_rapl.c index 3c67683..d6c74c1 100644
> --- a/drivers/powercap/intel_rapl.c
> +++ b/drivers/powercap/intel_rapl.c
> @@ -1369,6 +1369,9 @@ static int __init rapl_init(void)
>
> return -ENODEV;
> }
> +
> + cpu_notifier_register_begin();
> +
> /* prevent CPU hotplug during detection */
> get_online_cpus();
> ret = rapl_detect_topology();
> @@ -1380,20 +1383,23 @@ static int __init rapl_init(void)
> ret = -ENODEV;
> goto done;
> }
> - register_hotcpu_notifier(&rapl_cpu_notifier);
> + __register_hotcpu_notifier(&rapl_cpu_notifier);
> done:
> put_online_cpus();
> + cpu_notifier_register_done();
>
> return ret;
> }
>
> static void __exit rapl_exit(void)
> {
> + cpu_notifier_register_begin();
> get_online_cpus();
> - unregister_hotcpu_notifier(&rapl_cpu_notifier);
> + __unregister_hotcpu_notifier(&rapl_cpu_notifier);
> rapl_unregister_powercap();
> rapl_cleanup_data();
> put_online_cpus();
> + cpu_notifier_register_done();
> }
>
> module_init(rapl_init);
>
[Jacob Pan]
^ permalink raw reply [flat|nested] 63+ messages in thread
* [PATCH v3 33/52] scsi, bnx2i: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (31 preceding siblings ...)
2014-03-10 20:39 ` [PATCH v3 32/52] powercap, intel-rapl: " Srivatsa S. Bhat
@ 2014-03-10 20:39 ` Srivatsa S. Bhat
2014-03-10 20:39 ` [PATCH v3 34/52] scsi, bnx2fc: " Srivatsa S. Bhat
` (20 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:39 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-scsi, linux-pm,
linux-kernel, James E.J. Bottomley, linuxppc-dev,
Srivatsa S. Bhat, tj, paulmck, Eddie Wai, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the bnx2i code in scsi by using this latter form of callback registration.
Cc: Eddie Wai <eddie.wai@broadcom.com>
Cc: "James E.J. Bottomley" <JBottomley@parallels.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-scsi@vger.kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
drivers/scsi/bnx2i/bnx2i_init.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/drivers/scsi/bnx2i/bnx2i_init.c b/drivers/scsi/bnx2i/bnx2i_init.c
index 34c294b..80c03b4 100644
--- a/drivers/scsi/bnx2i/bnx2i_init.c
+++ b/drivers/scsi/bnx2i/bnx2i_init.c
@@ -537,11 +537,15 @@ static int __init bnx2i_mod_init(void)
p->iothread = NULL;
}
+ cpu_notifier_register_begin();
+
for_each_online_cpu(cpu)
bnx2i_percpu_thread_create(cpu);
/* Initialize per CPU interrupt thread */
- register_hotcpu_notifier(&bnx2i_cpu_notifier);
+ __register_hotcpu_notifier(&bnx2i_cpu_notifier);
+
+ cpu_notifier_register_done();
return 0;
@@ -581,11 +585,15 @@ static void __exit bnx2i_mod_exit(void)
}
mutex_unlock(&bnx2i_dev_lock);
- unregister_hotcpu_notifier(&bnx2i_cpu_notifier);
+ cpu_notifier_register_begin();
for_each_online_cpu(cpu)
bnx2i_percpu_thread_destroy(cpu);
+ __unregister_hotcpu_notifier(&bnx2i_cpu_notifier);
+
+ cpu_notifier_register_done();
+
iscsi_unregister_transport(&bnx2i_iscsi_transport);
cnic_unregister_driver(CNIC_ULP_ISCSI);
}
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 34/52] scsi, bnx2fc: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (32 preceding siblings ...)
2014-03-10 20:39 ` [PATCH v3 33/52] scsi, bnx2i: " Srivatsa S. Bhat
@ 2014-03-10 20:39 ` Srivatsa S. Bhat
2014-03-10 20:39 ` [PATCH v3 35/52] scsi, fcoe: " Srivatsa S. Bhat
` (19 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:39 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-scsi, linux-pm,
linux-kernel, James E.J. Bottomley, linuxppc-dev,
Srivatsa S. Bhat, tj, paulmck, Eddie Wai, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the bnx2fc code in scsi by using this latter form of callback
registration.
Cc: Eddie Wai <eddie.wai@broadcom.com>
Cc: "James E.J. Bottomley" <JBottomley@parallels.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-scsi@vger.kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
drivers/scsi/bnx2fc/bnx2fc_fcoe.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/drivers/scsi/bnx2fc/bnx2fc_fcoe.c b/drivers/scsi/bnx2fc/bnx2fc_fcoe.c
index 9b94850..c4ec235 100644
--- a/drivers/scsi/bnx2fc/bnx2fc_fcoe.c
+++ b/drivers/scsi/bnx2fc/bnx2fc_fcoe.c
@@ -2586,12 +2586,16 @@ static int __init bnx2fc_mod_init(void)
spin_lock_init(&p->fp_work_lock);
}
+ cpu_notifier_register_begin();
+
for_each_online_cpu(cpu) {
bnx2fc_percpu_thread_create(cpu);
}
/* Initialize per CPU interrupt thread */
- register_hotcpu_notifier(&bnx2fc_cpu_notifier);
+ __register_hotcpu_notifier(&bnx2fc_cpu_notifier);
+
+ cpu_notifier_register_done();
cnic_register_driver(CNIC_ULP_FCOE, &bnx2fc_cnic_cb);
@@ -2656,13 +2660,17 @@ static void __exit bnx2fc_mod_exit(void)
if (l2_thread)
kthread_stop(l2_thread);
- unregister_hotcpu_notifier(&bnx2fc_cpu_notifier);
+ cpu_notifier_register_begin();
/* Destroy per cpu threads */
for_each_online_cpu(cpu) {
bnx2fc_percpu_thread_destroy(cpu);
}
+ __unregister_hotcpu_notifier(&bnx2fc_cpu_notifier);
+
+ cpu_notifier_register_done();
+
destroy_workqueue(bnx2fc_wq);
/*
* detach from scsi transport
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 35/52] scsi, fcoe: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (33 preceding siblings ...)
2014-03-10 20:39 ` [PATCH v3 34/52] scsi, bnx2fc: " Srivatsa S. Bhat
@ 2014-03-10 20:39 ` Srivatsa S. Bhat
2014-03-10 20:39 ` [PATCH v3 36/52] zsmalloc: " Srivatsa S. Bhat
` (18 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:39 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-scsi, Robert Love,
linux-pm, linux-kernel, James E.J. Bottomley, fcoe-devel,
linuxppc-dev, Srivatsa S. Bhat, tj, paulmck, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the fcoe code in scsi by using this latter form of callback registration.
Cc: Robert Love <robert.w.love@intel.com>
Cc: "James E.J. Bottomley" <JBottomley@parallels.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: fcoe-devel@open-fcoe.org
Cc: linux-scsi@vger.kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
drivers/scsi/fcoe/fcoe.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
diff --git a/drivers/scsi/fcoe/fcoe.c b/drivers/scsi/fcoe/fcoe.c
index f317000..d5e105b 100644
--- a/drivers/scsi/fcoe/fcoe.c
+++ b/drivers/scsi/fcoe/fcoe.c
@@ -2633,14 +2633,18 @@ static int __init fcoe_init(void)
skb_queue_head_init(&p->fcoe_rx_list);
}
+ cpu_notifier_register_begin();
+
for_each_online_cpu(cpu)
fcoe_percpu_thread_create(cpu);
/* Initialize per CPU interrupt thread */
- rc = register_hotcpu_notifier(&fcoe_cpu_notifier);
+ rc = __register_hotcpu_notifier(&fcoe_cpu_notifier);
if (rc)
goto out_free;
+ cpu_notifier_register_done();
+
/* Setup link change notification */
fcoe_dev_setup();
@@ -2655,6 +2659,9 @@ out_free:
for_each_online_cpu(cpu) {
fcoe_percpu_thread_destroy(cpu);
}
+
+ cpu_notifier_register_done();
+
mutex_unlock(&fcoe_config_mutex);
destroy_workqueue(fcoe_wq);
return rc;
@@ -2687,11 +2694,15 @@ static void __exit fcoe_exit(void)
}
rtnl_unlock();
- unregister_hotcpu_notifier(&fcoe_cpu_notifier);
+ cpu_notifier_register_begin();
for_each_online_cpu(cpu)
fcoe_percpu_thread_destroy(cpu);
+ __unregister_hotcpu_notifier(&fcoe_cpu_notifier);
+
+ cpu_notifier_register_done();
+
mutex_unlock(&fcoe_config_mutex);
/*
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 36/52] zsmalloc: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (34 preceding siblings ...)
2014-03-10 20:39 ` [PATCH v3 35/52] scsi, fcoe: " Srivatsa S. Bhat
@ 2014-03-10 20:39 ` Srivatsa S. Bhat
2014-03-14 6:41 ` Minchan Kim
2014-03-10 20:40 ` [PATCH v3 37/52] acpi-cpufreq: " Srivatsa S. Bhat
` (17 subsequent siblings)
53 siblings, 1 reply; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:39 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, Minchan Kim,
linux-kernel, linux-mm, linuxppc-dev, Srivatsa S. Bhat, tj,
paulmck, Ingo Molnar, Nitin Gupta
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the zsmalloc code by using this latter form of callback registration.
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-mm@kvack.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
mm/zsmalloc.c | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index c03ca5e..36b4591 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -814,21 +814,32 @@ static void zs_exit(void)
{
int cpu;
+ cpu_notifier_register_begin();
+
for_each_online_cpu(cpu)
zs_cpu_notifier(NULL, CPU_DEAD, (void *)(long)cpu);
- unregister_cpu_notifier(&zs_cpu_nb);
+ __unregister_cpu_notifier(&zs_cpu_nb);
+
+ cpu_notifier_register_done();
}
static int zs_init(void)
{
int cpu, ret;
- register_cpu_notifier(&zs_cpu_nb);
+ cpu_notifier_register_begin();
+
+ __register_cpu_notifier(&zs_cpu_nb);
for_each_online_cpu(cpu) {
ret = zs_cpu_notifier(NULL, CPU_UP_PREPARE, (void *)(long)cpu);
- if (notifier_to_errno(ret))
+ if (notifier_to_errno(ret)) {
+ cpu_notifier_register_done();
goto fail;
+ }
}
+
+ cpu_notifier_register_done();
+
return 0;
fail:
zs_exit();
^ permalink raw reply related [flat|nested] 63+ messages in thread* Re: [PATCH v3 36/52] zsmalloc: Fix CPU hotplug callback registration
2014-03-10 20:39 ` [PATCH v3 36/52] zsmalloc: " Srivatsa S. Bhat
@ 2014-03-14 6:41 ` Minchan Kim
0 siblings, 0 replies; 63+ messages in thread
From: Minchan Kim @ 2014-03-14 6:41 UTC (permalink / raw)
To: Srivatsa S. Bhat
Cc: linux-arch, ego, walken, linux, akpm, linux-pm, peterz, rusty,
rjw, oleg, linux-kernel, linux-mm, linuxppc-dev, paulus, tj,
tglx, paulmck, mingo, Nitin Gupta
On Tue, Mar 11, 2014 at 02:09:59AM +0530, Srivatsa S. Bhat wrote:
> Subsystems that want to register CPU hotplug callbacks, as well as perform
> initialization for the CPUs that are already online, often do it as shown
> below:
>
> get_online_cpus();
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> register_cpu_notifier(&foobar_cpu_notifier);
>
> put_online_cpus();
>
> This is wrong, since it is prone to ABBA deadlocks involving the
> cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
> with CPU hotplug operations).
>
> Instead, the correct and race-free way of performing the callback
> registration is:
>
> cpu_notifier_register_begin();
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> /* Note the use of the double underscored version of the API */
> __register_cpu_notifier(&foobar_cpu_notifier);
>
> cpu_notifier_register_done();
>
>
> Fix the zsmalloc code by using this latter form of callback registration.
>
> Cc: Minchan Kim <minchan@kernel.org>
> Cc: Nitin Gupta <ngupta@vflare.org>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: linux-mm@kvack.org
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Thanks.
--
Kind regards,
Minchan Kim
^ permalink raw reply [flat|nested] 63+ messages in thread
* [PATCH v3 37/52] acpi-cpufreq: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (35 preceding siblings ...)
2014-03-10 20:39 ` [PATCH v3 36/52] zsmalloc: " Srivatsa S. Bhat
@ 2014-03-10 20:40 ` Srivatsa S. Bhat
2014-03-10 20:40 ` [PATCH v3 38/52] drivers/base/topology.c: " Srivatsa S. Bhat
` (16 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:40 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, Viresh Kumar,
Rafael J. Wysocki, linux-kernel, cpufreq, linuxppc-dev,
Srivatsa S. Bhat, tj, paulmck, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the acpi-cpufreq code by using this latter form of callback registration.
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: cpufreq@vger.kernel.org
Cc: linux-pm@vger.kernel.org
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
drivers/cpufreq/acpi-cpufreq.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
index 18448a7..245ae078e 100644
--- a/drivers/cpufreq/acpi-cpufreq.c
+++ b/drivers/cpufreq/acpi-cpufreq.c
@@ -907,15 +907,16 @@ static void __init acpi_cpufreq_boost_init(void)
acpi_cpufreq_driver.boost_supported = true;
acpi_cpufreq_driver.boost_enabled = boost_state(0);
- get_online_cpus();
+
+ cpu_notifier_register_begin();
/* Force all MSRs to the same value */
boost_set_msrs(acpi_cpufreq_driver.boost_enabled,
cpu_online_mask);
- register_cpu_notifier(&boost_nb);
+ __register_cpu_notifier(&boost_nb);
- put_online_cpus();
+ cpu_notifier_register_done();
}
}
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 38/52] drivers/base/topology.c: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (36 preceding siblings ...)
2014-03-10 20:40 ` [PATCH v3 37/52] acpi-cpufreq: " Srivatsa S. Bhat
@ 2014-03-10 20:40 ` Srivatsa S. Bhat
2014-03-10 20:40 ` [PATCH v3 39/52] clocksource, dummy-timer: " Srivatsa S. Bhat
` (15 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:40 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, Greg Kroah-Hartman,
linux-kernel, linuxppc-dev, Srivatsa S. Bhat, tj, paulmck,
Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the topology code by using this latter form of callback registration.
Cc: Ingo Molnar <mingo@kernel.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
drivers/base/topology.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/drivers/base/topology.c b/drivers/base/topology.c
index 94ffee3..a738d10 100644
--- a/drivers/base/topology.c
+++ b/drivers/base/topology.c
@@ -161,16 +161,20 @@ static int topology_cpu_callback(struct notifier_block *nfb,
static int topology_sysfs_init(void)
{
int cpu;
- int rc;
+ int rc = 0;
+
+ cpu_notifier_register_begin();
for_each_online_cpu(cpu) {
rc = topology_add_dev(cpu);
if (rc)
- return rc;
+ goto out;
}
- hotcpu_notifier(topology_cpu_callback, 0);
+ __hotcpu_notifier(topology_cpu_callback, 0);
- return 0;
+out:
+ cpu_notifier_register_done();
+ return rc;
}
device_initcall(topology_sysfs_init);
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 39/52] clocksource, dummy-timer: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (37 preceding siblings ...)
2014-03-10 20:40 ` [PATCH v3 38/52] drivers/base/topology.c: " Srivatsa S. Bhat
@ 2014-03-10 20:40 ` Srivatsa S. Bhat
2014-03-10 20:40 ` [PATCH v3 40/52] intel-idle: " Srivatsa S. Bhat
` (14 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:40 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, Daniel Lezcano,
linux-kernel, linuxppc-dev, Srivatsa S. Bhat, tj,
Thomas Gleixner, paulmck, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the clocksource dummy-timer code by using this latter form of callback
registration.
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
drivers/clocksource/dummy_timer.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/drivers/clocksource/dummy_timer.c b/drivers/clocksource/dummy_timer.c
index b3eb582..ad35725 100644
--- a/drivers/clocksource/dummy_timer.c
+++ b/drivers/clocksource/dummy_timer.c
@@ -56,14 +56,19 @@ static struct notifier_block dummy_timer_cpu_nb = {
static int __init dummy_timer_register(void)
{
- int err = register_cpu_notifier(&dummy_timer_cpu_nb);
+ int err = 0;
+
+ cpu_notifier_register_begin();
+ err = __register_cpu_notifier(&dummy_timer_cpu_nb);
if (err)
- return err;
+ goto out;
/* We won't get a call on the boot CPU, so register immediately */
if (num_possible_cpus() > 1)
dummy_timer_setup();
- return 0;
+out:
+ cpu_notifier_register_done();
+ return err;
}
early_initcall(dummy_timer_register);
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 40/52] intel-idle: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (38 preceding siblings ...)
2014-03-10 20:40 ` [PATCH v3 39/52] clocksource, dummy-timer: " Srivatsa S. Bhat
@ 2014-03-10 20:40 ` Srivatsa S. Bhat
2014-03-10 20:40 ` [PATCH v3 41/52] oprofile, nmi-timer: " Srivatsa S. Bhat
` (13 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:40 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, Rafael J. Wysocki,
linux-kernel, linuxppc-dev, Srivatsa S. Bhat, tj, paulmck,
Ingo Molnar, Len Brown
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the intel-idle code by using this latter form of callback registration.
Cc: Len Brown <lenb@kernel.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-pm@vger.kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
drivers/idle/intel_idle.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index 8e1939f..51493ed 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -681,14 +681,19 @@ static int __init intel_idle_init(void)
if (intel_idle_cpuidle_devices == NULL)
return -ENOMEM;
+ cpu_notifier_register_begin();
+
for_each_online_cpu(i) {
retval = intel_idle_cpu_init(i);
if (retval) {
+ cpu_notifier_register_done();
cpuidle_unregister_driver(&intel_idle_driver);
return retval;
}
}
- register_cpu_notifier(&cpu_hotplug_notifier);
+ __register_cpu_notifier(&cpu_hotplug_notifier);
+
+ cpu_notifier_register_done();
return 0;
}
@@ -698,10 +703,13 @@ static void __exit intel_idle_exit(void)
intel_idle_cpuidle_devices_uninit();
cpuidle_unregister_driver(&intel_idle_driver);
+ cpu_notifier_register_begin();
if (lapic_timer_reliable_states != LAPIC_TIMER_ALWAYS_RELIABLE)
on_each_cpu(__setup_broadcast_timer, (void *)false, 1);
- unregister_cpu_notifier(&cpu_hotplug_notifier);
+ __unregister_cpu_notifier(&cpu_hotplug_notifier);
+
+ cpu_notifier_register_done();
return;
}
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 41/52] oprofile, nmi-timer: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (39 preceding siblings ...)
2014-03-10 20:40 ` [PATCH v3 40/52] intel-idle: " Srivatsa S. Bhat
@ 2014-03-10 20:40 ` Srivatsa S. Bhat
2014-03-10 20:40 ` [PATCH v3 42/52] octeon, watchdog: " Srivatsa S. Bhat
` (12 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:40 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, linux-kernel,
linuxppc-dev, Srivatsa S. Bhat, tj, Robert Richter, paulmck,
Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the nmi-timer code in oprofile by using this latter form of callback
registration.
Cc: Robert Richter <rric@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
drivers/oprofile/nmi_timer_int.c | 23 +++++++++++++----------
1 file changed, 13 insertions(+), 10 deletions(-)
diff --git a/drivers/oprofile/nmi_timer_int.c b/drivers/oprofile/nmi_timer_int.c
index 76f1c93..9559829 100644
--- a/drivers/oprofile/nmi_timer_int.c
+++ b/drivers/oprofile/nmi_timer_int.c
@@ -108,8 +108,8 @@ static void nmi_timer_shutdown(void)
struct perf_event *event;
int cpu;
- get_online_cpus();
- unregister_cpu_notifier(&nmi_timer_cpu_nb);
+ cpu_notifier_register_begin();
+ __unregister_cpu_notifier(&nmi_timer_cpu_nb);
for_each_possible_cpu(cpu) {
event = per_cpu(nmi_timer_events, cpu);
if (!event)
@@ -119,7 +119,7 @@ static void nmi_timer_shutdown(void)
perf_event_release_kernel(event);
}
- put_online_cpus();
+ cpu_notifier_register_done();
}
static int nmi_timer_setup(void)
@@ -132,20 +132,23 @@ static int nmi_timer_setup(void)
do_div(period, HZ);
nmi_timer_attr.sample_period = period;
- get_online_cpus();
- err = register_cpu_notifier(&nmi_timer_cpu_nb);
+ cpu_notifier_register_begin();
+ err = __register_cpu_notifier(&nmi_timer_cpu_nb);
if (err)
goto out;
+
/* can't attach events to offline cpus: */
for_each_online_cpu(cpu) {
err = nmi_timer_start_cpu(cpu);
- if (err)
- break;
+ if (err) {
+ cpu_notifier_register_done();
+ nmi_timer_shutdown();
+ return err;
+ }
}
- if (err)
- nmi_timer_shutdown();
+
out:
- put_online_cpus();
+ cpu_notifier_register_done();
return err;
}
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 42/52] octeon, watchdog: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (40 preceding siblings ...)
2014-03-10 20:40 ` [PATCH v3 41/52] oprofile, nmi-timer: " Srivatsa S. Bhat
@ 2014-03-10 20:40 ` Srivatsa S. Bhat
2014-03-10 20:40 ` [PATCH v3 43/52] thermal, x86-pkg-temp: " Srivatsa S. Bhat
` (11 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:40 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-watchdog, linux-pm,
linux-kernel, linuxppc-dev, Wim Van Sebroeck, Srivatsa S. Bhat,
tj, paulmck, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the watchdog code in octeon by using this latter form of callback
registration.
Cc: Wim Van Sebroeck <wim@iguana.be>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-watchdog@vger.kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
drivers/watchdog/octeon-wdt-main.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/drivers/watchdog/octeon-wdt-main.c b/drivers/watchdog/octeon-wdt-main.c
index 4612088..4baf2d7 100644
--- a/drivers/watchdog/octeon-wdt-main.c
+++ b/drivers/watchdog/octeon-wdt-main.c
@@ -708,10 +708,13 @@ static int __init octeon_wdt_init(void)
cpumask_clear(&irq_enabled_cpus);
+ cpu_notifier_register_begin();
for_each_online_cpu(cpu)
octeon_wdt_setup_interrupt(cpu);
- register_hotcpu_notifier(&octeon_wdt_cpu_notifier);
+ __register_hotcpu_notifier(&octeon_wdt_cpu_notifier);
+ cpu_notifier_register_done();
+
out:
return ret;
}
@@ -725,7 +728,8 @@ static void __exit octeon_wdt_cleanup(void)
misc_deregister(&octeon_wdt_miscdev);
- unregister_hotcpu_notifier(&octeon_wdt_cpu_notifier);
+ cpu_notifier_register_begin();
+ __unregister_hotcpu_notifier(&octeon_wdt_cpu_notifier);
for_each_online_cpu(cpu) {
int core = cpu2core(cpu);
@@ -734,6 +738,9 @@ static void __exit octeon_wdt_cleanup(void)
/* Free the interrupt handler */
free_irq(OCTEON_IRQ_WDOG0 + core, octeon_wdt_poke_irq);
}
+
+ cpu_notifier_register_done();
+
/*
* Disable the boot-bus memory, the code it points to is soon
* to go missing.
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 43/52] thermal, x86-pkg-temp: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (41 preceding siblings ...)
2014-03-10 20:40 ` [PATCH v3 42/52] octeon, watchdog: " Srivatsa S. Bhat
@ 2014-03-10 20:40 ` Srivatsa S. Bhat
2014-03-10 20:41 ` [PATCH v3 44/52] hwmon, coretemp: " Srivatsa S. Bhat
` (10 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:40 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, linux-kernel,
Eduardo Valentin, linuxppc-dev, Srivatsa S. Bhat, tj, Zhang Rui,
paulmck, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the thermal x86-pkg-temp code by using this latter form of callback
registration.
Cc: Zhang Rui <rui.zhang@intel.com>
Cc: Eduardo Valentin <eduardo.valentin@ti.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-pm@vger.kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
drivers/thermal/x86_pkg_temp_thermal.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/drivers/thermal/x86_pkg_temp_thermal.c b/drivers/thermal/x86_pkg_temp_thermal.c
index 081fd7e..9ea3d9d 100644
--- a/drivers/thermal/x86_pkg_temp_thermal.c
+++ b/drivers/thermal/x86_pkg_temp_thermal.c
@@ -590,12 +590,12 @@ static int __init pkg_temp_thermal_init(void)
platform_thermal_package_rate_control =
pkg_temp_thermal_platform_thermal_rate_control;
- get_online_cpus();
+ cpu_notifier_register_begin();
for_each_online_cpu(i)
if (get_core_online(i))
goto err_ret;
- register_hotcpu_notifier(&pkg_temp_thermal_notifier);
- put_online_cpus();
+ __register_hotcpu_notifier(&pkg_temp_thermal_notifier);
+ cpu_notifier_register_done();
pkg_temp_debugfs_init(); /* Don't care if fails */
@@ -604,7 +604,7 @@ static int __init pkg_temp_thermal_init(void)
err_ret:
for_each_online_cpu(i)
put_core_offline(i);
- put_online_cpus();
+ cpu_notifier_register_done();
kfree(pkg_work_scheduled);
platform_thermal_package_notify = NULL;
platform_thermal_package_rate_control = NULL;
@@ -617,8 +617,8 @@ static void __exit pkg_temp_thermal_exit(void)
struct phy_dev_entry *phdev, *n;
int i;
- get_online_cpus();
- unregister_hotcpu_notifier(&pkg_temp_thermal_notifier);
+ cpu_notifier_register_begin();
+ __unregister_hotcpu_notifier(&pkg_temp_thermal_notifier);
mutex_lock(&phy_dev_list_mutex);
list_for_each_entry_safe(phdev, n, &phy_dev_list, list) {
/* Retore old MSR value for package thermal interrupt */
@@ -636,7 +636,7 @@ static void __exit pkg_temp_thermal_exit(void)
for_each_online_cpu(i)
cancel_delayed_work_sync(
&per_cpu(pkg_temp_thermal_threshold_work, i));
- put_online_cpus();
+ cpu_notifier_register_done();
kfree(pkg_work_scheduled);
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 44/52] hwmon, coretemp: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (42 preceding siblings ...)
2014-03-10 20:40 ` [PATCH v3 43/52] thermal, x86-pkg-temp: " Srivatsa S. Bhat
@ 2014-03-10 20:41 ` Srivatsa S. Bhat
2014-03-10 20:41 ` [PATCH v3 45/52] hwmon, via-cputemp: " Srivatsa S. Bhat
` (9 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:41 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, linux-kernel,
Fenghua Yu, lm-sensors, linuxppc-dev, Guenter Roeck,
Srivatsa S. Bhat, tj, paulmck, Ingo Molnar, Jean Delvare
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the hwmon coretemp code by using this latter form of callback
registration.
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Jean Delvare <jdelvare@suse.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: lm-sensors@lm-sensors.org
Acked-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
drivers/hwmon/coretemp.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c
index bbb0b0d..746a6ad 100644
--- a/drivers/hwmon/coretemp.c
+++ b/drivers/hwmon/coretemp.c
@@ -849,20 +849,20 @@ static int __init coretemp_init(void)
if (err)
goto exit;
- get_online_cpus();
+ cpu_notifier_register_begin();
for_each_online_cpu(i)
get_core_online(i);
#ifndef CONFIG_HOTPLUG_CPU
if (list_empty(&pdev_list)) {
- put_online_cpus();
+ cpu_notifier_register_done();
err = -ENODEV;
goto exit_driver_unreg;
}
#endif
- register_hotcpu_notifier(&coretemp_cpu_notifier);
- put_online_cpus();
+ __register_hotcpu_notifier(&coretemp_cpu_notifier);
+ cpu_notifier_register_done();
return 0;
#ifndef CONFIG_HOTPLUG_CPU
@@ -877,8 +877,8 @@ static void __exit coretemp_exit(void)
{
struct pdev_entry *p, *n;
- get_online_cpus();
- unregister_hotcpu_notifier(&coretemp_cpu_notifier);
+ cpu_notifier_register_begin();
+ __unregister_hotcpu_notifier(&coretemp_cpu_notifier);
mutex_lock(&pdev_list_mutex);
list_for_each_entry_safe(p, n, &pdev_list, list) {
platform_device_unregister(p->pdev);
@@ -886,7 +886,7 @@ static void __exit coretemp_exit(void)
kfree(p);
}
mutex_unlock(&pdev_list_mutex);
- put_online_cpus();
+ cpu_notifier_register_done();
platform_driver_unregister(&coretemp_driver);
}
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 45/52] hwmon, via-cputemp: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (43 preceding siblings ...)
2014-03-10 20:41 ` [PATCH v3 44/52] hwmon, coretemp: " Srivatsa S. Bhat
@ 2014-03-10 20:41 ` Srivatsa S. Bhat
2014-03-10 20:41 ` [PATCH v3 46/52] xen, balloon: " Srivatsa S. Bhat
` (8 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:41 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, linux-kernel,
lm-sensors, linuxppc-dev, Guenter Roeck, Srivatsa S. Bhat, tj,
paulmck, Ingo Molnar, Jean Delvare
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the hwmon via-cputemp code by using this latter form of callback
registration.
Cc: Jean Delvare <jdelvare@suse.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: lm-sensors@lm-sensors.org
Acked-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
drivers/hwmon/via-cputemp.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/drivers/hwmon/via-cputemp.c b/drivers/hwmon/via-cputemp.c
index 38944e9..8df43c5 100644
--- a/drivers/hwmon/via-cputemp.c
+++ b/drivers/hwmon/via-cputemp.c
@@ -319,7 +319,7 @@ static int __init via_cputemp_init(void)
if (err)
goto exit;
- get_online_cpus();
+ cpu_notifier_register_begin();
for_each_online_cpu(i) {
struct cpuinfo_x86 *c = &cpu_data(i);
@@ -339,14 +339,14 @@ static int __init via_cputemp_init(void)
#ifndef CONFIG_HOTPLUG_CPU
if (list_empty(&pdev_list)) {
- put_online_cpus();
+ cpu_notifier_register_done();
err = -ENODEV;
goto exit_driver_unreg;
}
#endif
- register_hotcpu_notifier(&via_cputemp_cpu_notifier);
- put_online_cpus();
+ __register_hotcpu_notifier(&via_cputemp_cpu_notifier);
+ cpu_notifier_register_done();
return 0;
#ifndef CONFIG_HOTPLUG_CPU
@@ -361,8 +361,8 @@ static void __exit via_cputemp_exit(void)
{
struct pdev_entry *p, *n;
- get_online_cpus();
- unregister_hotcpu_notifier(&via_cputemp_cpu_notifier);
+ cpu_notifier_register_begin();
+ __unregister_hotcpu_notifier(&via_cputemp_cpu_notifier);
mutex_lock(&pdev_list_mutex);
list_for_each_entry_safe(p, n, &pdev_list, list) {
platform_device_unregister(p->pdev);
@@ -370,7 +370,7 @@ static void __exit via_cputemp_exit(void)
kfree(p);
}
mutex_unlock(&pdev_list_mutex);
- put_online_cpus();
+ cpu_notifier_register_done();
platform_driver_unregister(&via_cputemp_driver);
}
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 46/52] xen, balloon: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (44 preceding siblings ...)
2014-03-10 20:41 ` [PATCH v3 45/52] hwmon, via-cputemp: " Srivatsa S. Bhat
@ 2014-03-10 20:41 ` Srivatsa S. Bhat
2014-03-10 20:41 ` [PATCH v3 47/52] trace, ring-buffer: " Srivatsa S. Bhat
` (7 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:41 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, Konrad Rzeszutek Wilk,
linux-kernel, linuxppc-dev, David Vrabel, Srivatsa S. Bhat, tj,
xen-devel, paulmck, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
The xen balloon driver doesn't take get/put_online_cpus() around this code,
but that is also buggy, since it can miss CPU hotplug events in between the
initialization and callback registration:
for_each_online_cpu(cpu)
init_cpu(cpu);
^
| Race window; Can miss CPU hotplug events here.
v
register_cpu_notifier(&foobar_cpu_notifier);
Interestingly, the balloon code in xen can simply be reorganized as shown
below, to have a race-free method to register hotplug callbacks, without even
taking get/put_online_cpus(). This is because the initialization performed for
already online CPUs is exactly the same as that performed for CPUs that come
online later. Moreover, the code has checks in place to avoid double
initialization.
register_cpu_notifier(&foobar_cpu_notifier);
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
put_online_cpus();
A hotplug operation that occurs between registering the notifier and calling
get_online_cpus(), won't disrupt anything, because the code takes care to
perform the memory allocations only once.
So reorganize the balloon code in xen this way to fix the issues with CPU
hotplug callback registration.
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: xen-devel@lists.xenproject.org
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
drivers/xen/balloon.c | 36 ++++++++++++++++++++++++------------
1 file changed, 24 insertions(+), 12 deletions(-)
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 37d06ea..dd79549 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -592,19 +592,29 @@ static void __init balloon_add_region(unsigned long start_pfn,
}
}
+static int alloc_balloon_scratch_page(int cpu)
+{
+ if (per_cpu(balloon_scratch_page, cpu) != NULL)
+ return 0;
+
+ per_cpu(balloon_scratch_page, cpu) = alloc_page(GFP_KERNEL);
+ if (per_cpu(balloon_scratch_page, cpu) == NULL) {
+ pr_warn("Failed to allocate balloon_scratch_page for cpu %d\n", cpu);
+ return -ENOMEM;
+ }
+
+ return 0;
+}
+
+
static int balloon_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu)
{
int cpu = (long)hcpu;
switch (action) {
case CPU_UP_PREPARE:
- if (per_cpu(balloon_scratch_page, cpu) != NULL)
- break;
- per_cpu(balloon_scratch_page, cpu) = alloc_page(GFP_KERNEL);
- if (per_cpu(balloon_scratch_page, cpu) == NULL) {
- pr_warn("Failed to allocate balloon_scratch_page for cpu %d\n", cpu);
+ if (alloc_balloon_scratch_page(cpu))
return NOTIFY_BAD;
- }
break;
default:
break;
@@ -624,15 +634,17 @@ static int __init balloon_init(void)
return -ENODEV;
if (!xen_feature(XENFEAT_auto_translated_physmap)) {
- for_each_online_cpu(cpu)
- {
- per_cpu(balloon_scratch_page, cpu) = alloc_page(GFP_KERNEL);
- if (per_cpu(balloon_scratch_page, cpu) == NULL) {
- pr_warn("Failed to allocate balloon_scratch_page for cpu %d\n", cpu);
+ register_cpu_notifier(&balloon_cpu_notifier);
+
+ get_online_cpus();
+ for_each_online_cpu(cpu) {
+ if (alloc_balloon_scratch_page(cpu)) {
+ put_online_cpus();
+ unregister_cpu_notifier(&balloon_cpu_notifier);
return -ENOMEM;
}
}
- register_cpu_notifier(&balloon_cpu_notifier);
+ put_online_cpus();
}
pr_info("Initialising balloon driver\n");
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 47/52] trace, ring-buffer: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (45 preceding siblings ...)
2014-03-10 20:41 ` [PATCH v3 46/52] xen, balloon: " Srivatsa S. Bhat
@ 2014-03-10 20:41 ` Srivatsa S. Bhat
2014-03-10 20:42 ` [PATCH v3 48/52] profile: " Srivatsa S. Bhat
` (6 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:41 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, Frederic Weisbecker,
linux-kernel, Steven Rostedt, linuxppc-dev, Srivatsa S. Bhat, tj,
paulmck, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the tracing ring-buffer code by using this latter form of callback
registration.
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
kernel/trace/ring_buffer.c | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index fc4da2d..c634868 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1301,7 +1301,7 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
* In that off case, we need to allocate for all possible cpus.
*/
#ifdef CONFIG_HOTPLUG_CPU
- get_online_cpus();
+ cpu_notifier_register_begin();
cpumask_copy(buffer->cpumask, cpu_online_mask);
#else
cpumask_copy(buffer->cpumask, cpu_possible_mask);
@@ -1324,10 +1324,10 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
#ifdef CONFIG_HOTPLUG_CPU
buffer->cpu_notify.notifier_call = rb_cpu_notify;
buffer->cpu_notify.priority = 0;
- register_cpu_notifier(&buffer->cpu_notify);
+ __register_cpu_notifier(&buffer->cpu_notify);
+ cpu_notifier_register_done();
#endif
- put_online_cpus();
mutex_init(&buffer->mutex);
return buffer;
@@ -1341,7 +1341,9 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
fail_free_cpumask:
free_cpumask_var(buffer->cpumask);
- put_online_cpus();
+#ifdef CONFIG_HOTPLUG_CPU
+ cpu_notifier_register_done();
+#endif
fail_free_buffer:
kfree(buffer);
@@ -1358,16 +1360,17 @@ ring_buffer_free(struct ring_buffer *buffer)
{
int cpu;
- get_online_cpus();
-
#ifdef CONFIG_HOTPLUG_CPU
- unregister_cpu_notifier(&buffer->cpu_notify);
+ cpu_notifier_register_begin();
+ __unregister_cpu_notifier(&buffer->cpu_notify);
#endif
for_each_buffer_cpu(buffer, cpu)
rb_free_cpu_buffer(buffer->buffers[cpu]);
- put_online_cpus();
+#ifdef CONFIG_HOTPLUG_CPU
+ cpu_notifier_register_done();
+#endif
kfree(buffer->buffers);
free_cpumask_var(buffer->cpumask);
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 48/52] profile: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (46 preceding siblings ...)
2014-03-10 20:41 ` [PATCH v3 47/52] trace, ring-buffer: " Srivatsa S. Bhat
@ 2014-03-10 20:42 ` Srivatsa S. Bhat
2014-03-10 20:42 ` [PATCH v3 49/52] mm, vmstat: " Srivatsa S. Bhat
` (5 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:42 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, Mauro Carvalho Chehab, linux-pm,
linux-kernel, linuxppc-dev, Al Viro, Srivatsa S. Bhat, tj,
paulmck, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the profile code by using this latter form of callback registration.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Mauro Carvalho Chehab <mchehab@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
kernel/profile.c | 20 +++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)
diff --git a/kernel/profile.c b/kernel/profile.c
index 6631e1e..4c0cb95 100644
--- a/kernel/profile.c
+++ b/kernel/profile.c
@@ -591,18 +591,28 @@ out_cleanup:
int __ref create_proc_profile(void) /* false positive from hotcpu_notifier */
{
struct proc_dir_entry *entry;
+ int err = 0;
if (!prof_on)
return 0;
- if (create_hash_tables())
- return -ENOMEM;
+
+ cpu_notifier_register_begin();
+
+ if (create_hash_tables()) {
+ err = -ENOMEM;
+ goto out;
+ }
+
entry = proc_create("profile", S_IWUSR | S_IRUGO,
NULL, &proc_profile_operations);
if (!entry)
- return 0;
+ goto out;
proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t));
- hotcpu_notifier(profile_cpu_callback, 0);
- return 0;
+ __hotcpu_notifier(profile_cpu_callback, 0);
+
+out:
+ cpu_notifier_register_done();
+ return err;
}
module_init(create_proc_profile);
#endif /* CONFIG_PROC_FS */
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 49/52] mm, vmstat: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (47 preceding siblings ...)
2014-03-10 20:42 ` [PATCH v3 48/52] profile: " Srivatsa S. Bhat
@ 2014-03-10 20:42 ` Srivatsa S. Bhat
2014-03-10 20:42 ` [PATCH v3 50/52] mm, zswap: " Srivatsa S. Bhat
` (4 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:42 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, Christoph Lameter, walken, linux, linux-pm,
Rik van Riel, linux-kernel, linux-mm, linuxppc-dev, Dave Hansen,
Srivatsa S. Bhat, Johannes Weiner, tj, Toshi Kani, Andrew Morton,
paulmck, Cody P Schafer, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the vmstat code in the MM subsystem by using this latter form of callback
registration.
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Cody P Schafer <cody@linux.vnet.ibm.com>
Cc: Toshi Kani <toshi.kani@hp.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-mm@kvack.org
Acked-by: Christoph Lameter <cl@linux.com>
Acked-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
mm/vmstat.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/mm/vmstat.c b/mm/vmstat.c
index def5dd2..58c6f3d 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1292,14 +1292,14 @@ static int __init setup_vmstat(void)
#ifdef CONFIG_SMP
int cpu;
- register_cpu_notifier(&vmstat_notifier);
+ cpu_notifier_register_begin();
+ __register_cpu_notifier(&vmstat_notifier);
- get_online_cpus();
for_each_online_cpu(cpu) {
start_cpu_timer(cpu);
node_set_state(cpu_to_node(cpu), N_CPU);
}
- put_online_cpus();
+ cpu_notifier_register_done();
#endif
#ifdef CONFIG_PROC_FS
proc_create("buddyinfo", S_IRUGO, NULL, &fragmentation_file_operations);
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 50/52] mm, zswap: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (48 preceding siblings ...)
2014-03-10 20:42 ` [PATCH v3 49/52] mm, vmstat: " Srivatsa S. Bhat
@ 2014-03-10 20:42 ` Srivatsa S. Bhat
2014-03-10 20:42 ` [PATCH v3 51/52] net/core/flow.c: " Srivatsa S. Bhat
` (3 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:42 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, linux-kernel, linux-mm,
linuxppc-dev, Srivatsa S. Bhat, tj, paulmck, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the zswap code by using this latter form of callback registration.
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-mm@kvack.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
mm/zswap.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/mm/zswap.c b/mm/zswap.c
index e55bab9..d7337fb 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -387,18 +387,18 @@ static int zswap_cpu_init(void)
{
unsigned long cpu;
- get_online_cpus();
+ cpu_notifier_register_begin();
for_each_online_cpu(cpu)
if (__zswap_cpu_notifier(CPU_UP_PREPARE, cpu) != NOTIFY_OK)
goto cleanup;
- register_cpu_notifier(&zswap_cpu_notifier_block);
- put_online_cpus();
+ __register_cpu_notifier(&zswap_cpu_notifier_block);
+ cpu_notifier_register_done();
return 0;
cleanup:
for_each_online_cpu(cpu)
__zswap_cpu_notifier(CPU_UP_CANCELED, cpu);
- put_online_cpus();
+ cpu_notifier_register_done();
return -ENOMEM;
}
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 51/52] net/core/flow.c: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (49 preceding siblings ...)
2014-03-10 20:42 ` [PATCH v3 50/52] mm, zswap: " Srivatsa S. Bhat
@ 2014-03-10 20:42 ` Srivatsa S. Bhat
2014-03-10 20:42 ` [PATCH v3 52/52] net/iucv/iucv.c: " Srivatsa S. Bhat
` (2 subsequent siblings)
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:42 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, Li RongQing, netdev,
linux-kernel, Chris Metcalf, David S. Miller, linuxppc-dev,
Srivatsa S. Bhat, tj, Sasha Levin, Andrew Morton, paulmck,
Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the code in net/core/flow.c by using this latter form of callback
registration.
Cc: Li RongQing <roy.qing.li@gmail.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: netdev@vger.kernel.org
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
net/core/flow.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/net/core/flow.c b/net/core/flow.c
index dfa602c..9a2151f 100644
--- a/net/core/flow.c
+++ b/net/core/flow.c
@@ -456,6 +456,8 @@ static int __init flow_cache_init(struct flow_cache *fc)
if (!fc->percpu)
return -ENOMEM;
+ cpu_notifier_register_begin();
+
for_each_online_cpu(i) {
if (flow_cache_cpu_prepare(fc, i))
goto err;
@@ -463,7 +465,9 @@ static int __init flow_cache_init(struct flow_cache *fc)
fc->hotcpu_notifier = (struct notifier_block){
.notifier_call = flow_cache_cpu,
};
- register_hotcpu_notifier(&fc->hotcpu_notifier);
+ __register_hotcpu_notifier(&fc->hotcpu_notifier);
+
+ cpu_notifier_register_done();
setup_timer(&fc->rnd_timer, flow_cache_new_hashrnd,
(unsigned long) fc);
@@ -479,6 +483,8 @@ err:
fcp->hash_table = NULL;
}
+ cpu_notifier_register_done();
+
free_percpu(fc->percpu);
fc->percpu = NULL;
^ permalink raw reply related [flat|nested] 63+ messages in thread* [PATCH v3 52/52] net/iucv/iucv.c: Fix CPU hotplug callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (50 preceding siblings ...)
2014-03-10 20:42 ` [PATCH v3 51/52] net/core/flow.c: " Srivatsa S. Bhat
@ 2014-03-10 20:42 ` Srivatsa S. Bhat
2014-03-11 0:31 ` [PATCH v3 00/52] CPU hotplug: Fix issues with " Rafael J. Wysocki
2014-03-11 22:07 ` Andrew Morton
53 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-10 20:42 UTC (permalink / raw)
To: paulus, oleg, mingo, rjw, rusty, peterz, tglx, akpm
Cc: linux-arch, ego, walken, linux, linux-pm, linux-s390,
linux-kernel, Ursula Braun, linuxppc-dev, David S. Miller,
Srivatsa S. Bhat, netdev, tj, paulmck, Ingo Molnar
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the code in net/iucv/iucv.c by using this latter form of callback
registration. Also, provide helper functions to perform the common memory
allocations and frees, to condense repetitive code.
Cc: Ursula Braun <ursula.braun@de.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-s390@vger.kernel.org
Cc: netdev@vger.kernel.org
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
net/iucv/iucv.c | 121 ++++++++++++++++++++++++++-----------------------------
1 file changed, 57 insertions(+), 64 deletions(-)
diff --git a/net/iucv/iucv.c b/net/iucv/iucv.c
index cd5b8ec..79a0ce9 100644
--- a/net/iucv/iucv.c
+++ b/net/iucv/iucv.c
@@ -621,6 +621,42 @@ static void iucv_disable(void)
put_online_cpus();
}
+static void free_iucv_data(int cpu)
+{
+ kfree(iucv_param_irq[cpu]);
+ iucv_param_irq[cpu] = NULL;
+ kfree(iucv_param[cpu]);
+ iucv_param[cpu] = NULL;
+ kfree(iucv_irq_data[cpu]);
+ iucv_irq_data[cpu] = NULL;
+}
+
+static int alloc_iucv_data(int cpu)
+{
+ /* Note: GFP_DMA used to get memory below 2G */
+ iucv_irq_data[cpu] = kmalloc_node(sizeof(struct iucv_irq_data),
+ GFP_KERNEL|GFP_DMA, cpu_to_node(cpu));
+ if (!iucv_irq_data[cpu])
+ goto out_free;
+
+ /* Allocate parameter blocks. */
+ iucv_param[cpu] = kmalloc_node(sizeof(union iucv_param),
+ GFP_KERNEL|GFP_DMA, cpu_to_node(cpu));
+ if (!iucv_param[cpu])
+ goto out_free;
+
+ iucv_param_irq[cpu] = kmalloc_node(sizeof(union iucv_param),
+ GFP_KERNEL|GFP_DMA, cpu_to_node(cpu));
+ if (!iucv_param_irq[cpu])
+ goto out_free;
+
+ return 0;
+
+out_free:
+ free_iucv_data(cpu);
+ return -ENOMEM;
+}
+
static int iucv_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu)
{
@@ -630,38 +666,14 @@ static int iucv_cpu_notify(struct notifier_block *self,
switch (action) {
case CPU_UP_PREPARE:
case CPU_UP_PREPARE_FROZEN:
- iucv_irq_data[cpu] = kmalloc_node(sizeof(struct iucv_irq_data),
- GFP_KERNEL|GFP_DMA, cpu_to_node(cpu));
- if (!iucv_irq_data[cpu])
- return notifier_from_errno(-ENOMEM);
-
- iucv_param[cpu] = kmalloc_node(sizeof(union iucv_param),
- GFP_KERNEL|GFP_DMA, cpu_to_node(cpu));
- if (!iucv_param[cpu]) {
- kfree(iucv_irq_data[cpu]);
- iucv_irq_data[cpu] = NULL;
+ if (alloc_iucv_data(cpu))
return notifier_from_errno(-ENOMEM);
- }
- iucv_param_irq[cpu] = kmalloc_node(sizeof(union iucv_param),
- GFP_KERNEL|GFP_DMA, cpu_to_node(cpu));
- if (!iucv_param_irq[cpu]) {
- kfree(iucv_param[cpu]);
- iucv_param[cpu] = NULL;
- kfree(iucv_irq_data[cpu]);
- iucv_irq_data[cpu] = NULL;
- return notifier_from_errno(-ENOMEM);
- }
break;
case CPU_UP_CANCELED:
case CPU_UP_CANCELED_FROZEN:
case CPU_DEAD:
case CPU_DEAD_FROZEN:
- kfree(iucv_param_irq[cpu]);
- iucv_param_irq[cpu] = NULL;
- kfree(iucv_param[cpu]);
- iucv_param[cpu] = NULL;
- kfree(iucv_irq_data[cpu]);
- iucv_irq_data[cpu] = NULL;
+ free_iucv_data(cpu);
break;
case CPU_ONLINE:
case CPU_ONLINE_FROZEN:
@@ -2025,33 +2037,20 @@ static int __init iucv_init(void)
goto out_int;
}
- for_each_online_cpu(cpu) {
- /* Note: GFP_DMA used to get memory below 2G */
- iucv_irq_data[cpu] = kmalloc_node(sizeof(struct iucv_irq_data),
- GFP_KERNEL|GFP_DMA, cpu_to_node(cpu));
- if (!iucv_irq_data[cpu]) {
- rc = -ENOMEM;
- goto out_free;
- }
+ cpu_notifier_register_begin();
- /* Allocate parameter blocks. */
- iucv_param[cpu] = kmalloc_node(sizeof(union iucv_param),
- GFP_KERNEL|GFP_DMA, cpu_to_node(cpu));
- if (!iucv_param[cpu]) {
- rc = -ENOMEM;
- goto out_free;
- }
- iucv_param_irq[cpu] = kmalloc_node(sizeof(union iucv_param),
- GFP_KERNEL|GFP_DMA, cpu_to_node(cpu));
- if (!iucv_param_irq[cpu]) {
+ for_each_online_cpu(cpu) {
+ if (alloc_iucv_data(cpu)) {
rc = -ENOMEM;
goto out_free;
}
-
}
- rc = register_hotcpu_notifier(&iucv_cpu_notifier);
+ rc = __register_hotcpu_notifier(&iucv_cpu_notifier);
if (rc)
goto out_free;
+
+ cpu_notifier_register_done();
+
rc = register_reboot_notifier(&iucv_reboot_notifier);
if (rc)
goto out_cpu;
@@ -2069,16 +2068,14 @@ static int __init iucv_init(void)
out_reboot:
unregister_reboot_notifier(&iucv_reboot_notifier);
out_cpu:
- unregister_hotcpu_notifier(&iucv_cpu_notifier);
+ cpu_notifier_register_begin();
+ __unregister_hotcpu_notifier(&iucv_cpu_notifier);
out_free:
- for_each_possible_cpu(cpu) {
- kfree(iucv_param_irq[cpu]);
- iucv_param_irq[cpu] = NULL;
- kfree(iucv_param[cpu]);
- iucv_param[cpu] = NULL;
- kfree(iucv_irq_data[cpu]);
- iucv_irq_data[cpu] = NULL;
- }
+ for_each_possible_cpu(cpu)
+ free_iucv_data(cpu);
+
+ cpu_notifier_register_done();
+
root_device_unregister(iucv_root);
out_int:
unregister_external_interrupt(0x4000, iucv_external_interrupt);
@@ -2105,15 +2102,11 @@ static void __exit iucv_exit(void)
kfree(p);
spin_unlock_irq(&iucv_queue_lock);
unregister_reboot_notifier(&iucv_reboot_notifier);
- unregister_hotcpu_notifier(&iucv_cpu_notifier);
- for_each_possible_cpu(cpu) {
- kfree(iucv_param_irq[cpu]);
- iucv_param_irq[cpu] = NULL;
- kfree(iucv_param[cpu]);
- iucv_param[cpu] = NULL;
- kfree(iucv_irq_data[cpu]);
- iucv_irq_data[cpu] = NULL;
- }
+ cpu_notifier_register_begin();
+ __unregister_hotcpu_notifier(&iucv_cpu_notifier);
+ for_each_possible_cpu(cpu)
+ free_iucv_data(cpu);
+ cpu_notifier_register_done();
root_device_unregister(iucv_root);
bus_unregister(&iucv_bus);
unregister_external_interrupt(0x4000, iucv_external_interrupt);
^ permalink raw reply related [flat|nested] 63+ messages in thread* Re: [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (51 preceding siblings ...)
2014-03-10 20:42 ` [PATCH v3 52/52] net/iucv/iucv.c: " Srivatsa S. Bhat
@ 2014-03-11 0:31 ` Rafael J. Wysocki
2014-03-11 22:07 ` Andrew Morton
53 siblings, 0 replies; 63+ messages in thread
From: Rafael J. Wysocki @ 2014-03-11 0:31 UTC (permalink / raw)
To: Srivatsa S. Bhat
Cc: linux-arch, ego, walken, linux, akpm, linux-pm, peterz, rusty,
oleg, linux-kernel, linuxppc-dev, paulus, tj, tglx, paulmck,
mingo
On Tuesday, March 11, 2014 02:03:52 AM Srivatsa S. Bhat wrote:
> Hi,
Hi,
> Many subsystems and drivers have the need to register CPU hotplug callbacks
> from their init routines and also perform initialization for the CPUs that are
> already online. But unfortunately there is no race-free way to achieve this
> today.
>
> For example, consider this piece of code:
>
> get_online_cpus();
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> register_cpu_notifier(&foobar_cpu_notifier);
>
> put_online_cpus();
>
> This is not safe because there is a possibility of an ABBA deadlock involving
> the cpu_add_remove_lock and the cpu_hotplug.lock.
>
> CPU 0 CPU 1
> ----- -----
>
> Acquire cpu_hotplug.lock
> [via get_online_cpus()]
>
> CPU online/offline operation
> takes cpu_add_remove_lock
> [via cpu_maps_update_begin()]
>
> Try to acquire
> cpu_add_remove_lock
> [via register_cpu_notifier()]
>
> CPU online/offline operation
> tries to acquire cpu_hotplug.lock
> [via cpu_hotplug_begin()]
>
> *** DEADLOCK! ***
>
>
> Other combinations of callback registration also don't work correctly.
> Examples:
>
> register_cpu_notifier(&foobar_cpu_notifier);
>
> get_online_cpus();
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> put_online_cpus();
>
> This can lead to double initialization if a hotplug operation occurs after
> registering the notifier and before invoking get_online_cpus().
>
> On the other hand, the following piece of code can miss hotplug events
> altogether:
>
> get_online_cpus();
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> put_online_cpus();
> ^
> | Race window; Can miss hotplug events here
> v
> register_cpu_notifier(&foobar_cpu_notifier);
>
>
> To solve these issues and provide a race-free method to register CPU hotplug
> callbacks, this patchset introduces new variants of the callback registration
> APIs that don't hold the cpu_add_remove_lock, and exports the
> cpu_add_remove_lock via 2 new APIs cpu_notifier_register_begin/done() for use
> by various subsystems. With this in place, the following code snippet will
> register a hotplug callback as well as initialize already online CPUs without
> any race conditions.
>
> cpu_notifier_register_begin();
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> /* This doesn't take the cpu_add_remove_lock */
> __register_cpu_notifier(&foobar_cpu_notifier);
>
> cpu_notifier_register_done();
>
>
> In this patchset, patch 1 adds lockdep annotations to catch the above mentioned
> deadlock scenario. Patch 2 introduces the new APIs and infrastructure necessary
> for race-free callback registration. The remaining patches perform tree-wide
> conversions (to use this model).
>
> This patchset has been hosted in the below git tree. It applies cleanly on
> v3.14-rc6.
>
> git://github.com/srivatsabhat/linux.git cpuhp-registration-fixes-v3
So to me, this is a useful patchset and it addresses a real problem. It has
gone through several rounds of review and recently I haven't really seen any
objections against is from anyone. On the contrary, I've seen ACKs from a
number of people whom I trust.
Thus, if nobody objects, I'm going to take this series into the PM tree for 3.15.
Thanks!
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
^ permalink raw reply [flat|nested] 63+ messages in thread* Re: [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration
2014-03-10 20:33 [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration Srivatsa S. Bhat
` (52 preceding siblings ...)
2014-03-11 0:31 ` [PATCH v3 00/52] CPU hotplug: Fix issues with " Rafael J. Wysocki
@ 2014-03-11 22:07 ` Andrew Morton
2014-03-12 20:48 ` Srivatsa S. Bhat
53 siblings, 1 reply; 63+ messages in thread
From: Andrew Morton @ 2014-03-11 22:07 UTC (permalink / raw)
To: Srivatsa S. Bhat
Cc: linux-arch, ego, walken, linux, linux-pm, peterz, rusty, rjw,
oleg, linux-kernel, linuxppc-dev, paulus, tj, tglx, paulmck,
mingo
On Tue, 11 Mar 2014 02:03:52 +0530 "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com> wrote:
> Hi,
>
> Many subsystems and drivers have the need to register CPU hotplug callbacks
> from their init routines and also perform initialization for the CPUs that are
> already online. But unfortunately there is no race-free way to achieve this
> today.
>
> For example, consider this piece of code:
>
> get_online_cpus();
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> register_cpu_notifier(&foobar_cpu_notifier);
>
> put_online_cpus();
>
> This is not safe because there is a possibility of an ABBA deadlock involving
> the cpu_add_remove_lock and the cpu_hotplug.lock.
>
> CPU 0 CPU 1
> ----- -----
>
> Acquire cpu_hotplug.lock
> [via get_online_cpus()]
>
> CPU online/offline operation
> takes cpu_add_remove_lock
> [via cpu_maps_update_begin()]
>
> Try to acquire
> cpu_add_remove_lock
> [via register_cpu_notifier()]
>
> CPU online/offline operation
> tries to acquire cpu_hotplug.lock
> [via cpu_hotplug_begin()]
Can't we fix this by using a different (ie: new) lock to protect
cpu_chain?
^ permalink raw reply [flat|nested] 63+ messages in thread* Re: [PATCH v3 00/52] CPU hotplug: Fix issues with callback registration
2014-03-11 22:07 ` Andrew Morton
@ 2014-03-12 20:48 ` Srivatsa S. Bhat
0 siblings, 0 replies; 63+ messages in thread
From: Srivatsa S. Bhat @ 2014-03-12 20:48 UTC (permalink / raw)
To: Andrew Morton
Cc: linux-arch, ego, walken, linux, linux-pm, peterz, rusty, rjw,
oleg, linux-kernel, linuxppc-dev, paulus, tj, tglx, paulmck,
mingo
On 03/12/2014 03:37 AM, Andrew Morton wrote:
> On Tue, 11 Mar 2014 02:03:52 +0530 "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com> wrote:
>
>> Hi,
>>
>> Many subsystems and drivers have the need to register CPU hotplug callbacks
>> from their init routines and also perform initialization for the CPUs that are
>> already online. But unfortunately there is no race-free way to achieve this
>> today.
>>
>> For example, consider this piece of code:
>>
>> get_online_cpus();
>>
>> for_each_online_cpu(cpu)
>> init_cpu(cpu);
>>
>> register_cpu_notifier(&foobar_cpu_notifier);
>>
>> put_online_cpus();
>>
>> This is not safe because there is a possibility of an ABBA deadlock involving
>> the cpu_add_remove_lock and the cpu_hotplug.lock.
>>
>> CPU 0 CPU 1
>> ----- -----
>>
>> Acquire cpu_hotplug.lock
>> [via get_online_cpus()]
>>
>> CPU online/offline operation
>> takes cpu_add_remove_lock
>> [via cpu_maps_update_begin()]
>>
>> Try to acquire
>> cpu_add_remove_lock
>> [via register_cpu_notifier()]
>>
>> CPU online/offline operation
>> tries to acquire cpu_hotplug.lock
>> [via cpu_hotplug_begin()]
>
> Can't we fix this by using a different (ie: new) lock to protect
> cpu_chain?
>
No, that won't be a better solution than this one :-( The reason is that
CPU_POST_DEAD notifiers are invoked with the cpu_hotplug.lock dropped (by
design). So if we introduce the new lock, the locking would look as shown
below at the CPU hotplug side:
[ Note that it is unsafe to acquire and release the cpu-chain lock separately
for each invocation of the notifiers, because that would allow manipulations
of the cpu-chain in between two sets of notifications (such as CPU_DOWN_PREPARE
and CPU_DEAD, corresponding to the same CPU hotplug operation), which is
clearly wrong. So we need to acquire the new lock at the very beginning of
the hotplug operation and release it at the very end, after all notifiers
have been invoked.]
cpu_maps_update_begin(); //acquire cpu_add_remove_lock
cpu_hotplug_begin(); //acquire cpu_hotplug.lock
cpu_chain_lock(); //acquire a new lock that protects the cpu_chain
Invoke CPU_DOWN_PREPARE notifiers
//take cpu offline using stop-machine
Invoke CPU_DEAD notifiers
cpu_hotplug_done(); //release cpu_hotplug.lock
Invoke CPU_POST_DEAD notifiers
cpu_chain_unlock(); //release a new lock that protects the cpu_chain
cpu_maps_update_done(); //release cpu_add_remove_lock
So, if you observe the nesting of locks, it looks weird, because
cpu_hotplug.lock is acquired first, followed by cpu_chain_lock,
but they are released in the same order! IOW, they don't nest "properly".
To avoid this, if we reorder the locks in such a way that cpu_chain_lock
is the outer lock compared to cpu_hotplug.lock, then it becomes exactly
same as cpu_add_remove_lock. In other words, we can reuse the
cpu_add_remove_lock for this very purpose of protecting the cpu-chains
without adding any new lock to the CPU hotplug core code. And this is
what the existing code already does. I just utilize this fact and make
sure that we don't deadlock in the scenarios mentioned in the cover-letter
of this patchset.
Regards,
Srivatsa S. Bhat
^ permalink raw reply [flat|nested] 63+ messages in thread