* [PATCH 1/3] notifier: Fix broken error handling pattern
[not found] <20190624091843.859714294@infradead.org>
@ 2019-06-24 9:18 ` Peter Zijlstra
2019-06-24 22:21 ` Josh Poimboeuf
0 siblings, 1 reply; 5+ messages in thread
From: Peter Zijlstra @ 2019-06-24 9:18 UTC (permalink / raw)
To: Jessica Yu, linux-kernel, jpoimboe, jikos, mbenes, pmladek, ast,
daniel, akpm, peterz
Cc: Rafael J. Wysocki, Pavel Machek, Len Brown, Sam Protsenko,
Thomas Gleixner, Greg Kroah-Hartman, Alexios Zavras,
Allison Randal, Vasily Averin, Todd Brandt, linux-pm
The current notifiers have the following error handling pattern all
over the place:
int nr;
ret = __foo_notifier_call_chain(&chain, val_up, v, -1, &nr);
if (err & NOTIFIER_STOP_MASK)
__foo_notifier_call_chain(&chain, val_down, v, nr-1, NULL)
And aside from the endless repetition thereof, it is broken. Consider
blocking notifiers; both calls take and drop the rwsem, this means
that the notifier list can change in between the two calls, making @nr
meaningless.
Fix this by replacing all the __foo_notifier_call_chain() functions
with foo_notifier_call_chain_error() that embeds the above patter, but
ensures it is inside a single lock region.
XXX: It is probably still broken for the RCU (atomic, src) users
(cpu_pm_notifier).
Note: software_resume() error handling was broken afaict.
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Len Brown <len.brown@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Sam Protsenko <semen.protsenko@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Alexios Zavras <alexios.zavras@intel.com>
Cc: Allison Randal <allison@lohutok.net>
Cc: Vasily Averin <vvs@virtuozzo.com>
Cc: Todd Brandt <todd.e.brandt@linux.intel.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-pm@vger.kernel.org
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
include/linux/notifier.h | 17 ++-
kernel/cpu_pm.c | 51 +++++------
kernel/notifier.c | 159 +++++++++++++------------------------
kernel/power/hibernate.c | 26 ++----
kernel/power/main.c | 8 -
kernel/power/power.h | 3
kernel/power/suspend.c | 14 +--
kernel/power/user.c | 14 ---
tools/power/pm-graph/sleepgraph.py | 2
9 files changed, 118 insertions(+), 176 deletions(-)
--- a/include/linux/notifier.h
+++ b/include/linux/notifier.h
@@ -165,20 +165,21 @@ extern int srcu_notifier_chain_unregiste
extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
unsigned long val, void *v);
-extern int __atomic_notifier_call_chain(struct atomic_notifier_head *nh,
- unsigned long val, void *v, int nr_to_call, int *nr_calls);
extern int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
unsigned long val, void *v);
-extern int __blocking_notifier_call_chain(struct blocking_notifier_head *nh,
- unsigned long val, void *v, int nr_to_call, int *nr_calls);
extern int raw_notifier_call_chain(struct raw_notifier_head *nh,
unsigned long val, void *v);
-extern int __raw_notifier_call_chain(struct raw_notifier_head *nh,
- unsigned long val, void *v, int nr_to_call, int *nr_calls);
extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
unsigned long val, void *v);
-extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
- unsigned long val, void *v, int nr_to_call, int *nr_calls);
+
+extern int atomic_notifier_call_chain_error(struct atomic_notifier_head *nh,
+ unsigned long val_up, unsigned long val_down, void *v);
+extern int blocking_notifier_call_chain_error(struct blocking_notifier_head *nh,
+ unsigned long val_up, unsigned long val_down, void *v);
+extern int raw_notifier_call_chain_error(struct raw_notifier_head *nh,
+ unsigned long val_up, unsigned long val_down, void *v);
+extern int srcu_notifier_call_chain_error(struct srcu_notifier_head *nh,
+ unsigned long val_up, unsigned long val_down, void *v);
#define NOTIFY_DONE 0x0000 /* Don't care */
#define NOTIFY_OK 0x0001 /* Suits me */
--- a/kernel/cpu_pm.c
+++ b/kernel/cpu_pm.c
@@ -15,7 +15,7 @@
static ATOMIC_NOTIFIER_HEAD(cpu_pm_notifier_chain);
-static int cpu_pm_notify(enum cpu_pm_event event, int nr_to_call, int *nr_calls)
+static int cpu_pm_notify(enum cpu_pm_event event)
{
int ret;
@@ -25,8 +25,23 @@ static int cpu_pm_notify(enum cpu_pm_eve
* RCU know this.
*/
rcu_irq_enter_irqson();
- ret = __atomic_notifier_call_chain(&cpu_pm_notifier_chain, event, NULL,
- nr_to_call, nr_calls);
+ ret = atomic_notifier_call_chain(&cpu_pm_notifier_chain, event, NULL);
+ rcu_irq_exit_irqson();
+
+ return notifier_to_errno(ret);
+}
+
+static int cpu_pm_notify_error(enum cpu_pm_event event_up, enum cpu_pm_event event_down)
+{
+ int ret;
+
+ /*
+ * __atomic_notifier_call_chain has a RCU read critical section, which
+ * could be disfunctional in cpu idle. Copy RCU_NONIDLE code to let
+ * RCU know this.
+ */
+ rcu_irq_enter_irqson();
+ ret = atomic_notifier_call_chain_error(&cpu_pm_notifier_chain, event_up, event_down, NULL);
rcu_irq_exit_irqson();
return notifier_to_errno(ret);
@@ -80,18 +95,7 @@ EXPORT_SYMBOL_GPL(cpu_pm_unregister_noti
*/
int cpu_pm_enter(void)
{
- int nr_calls;
- int ret = 0;
-
- ret = cpu_pm_notify(CPU_PM_ENTER, -1, &nr_calls);
- if (ret)
- /*
- * Inform listeners (nr_calls - 1) about failure of CPU PM
- * PM entry who are notified earlier to prepare for it.
- */
- cpu_pm_notify(CPU_PM_ENTER_FAILED, nr_calls - 1, NULL);
-
- return ret;
+ return cpu_pm_notify_error(CPU_PM_ENTER, CPU_PM_ENTER_FAILED);
}
EXPORT_SYMBOL_GPL(cpu_pm_enter);
@@ -109,7 +113,7 @@ EXPORT_SYMBOL_GPL(cpu_pm_enter);
*/
int cpu_pm_exit(void)
{
- return cpu_pm_notify(CPU_PM_EXIT, -1, NULL);
+ return cpu_pm_notify(CPU_PM_EXIT);
}
EXPORT_SYMBOL_GPL(cpu_pm_exit);
@@ -131,18 +135,7 @@ EXPORT_SYMBOL_GPL(cpu_pm_exit);
*/
int cpu_cluster_pm_enter(void)
{
- int nr_calls;
- int ret = 0;
-
- ret = cpu_pm_notify(CPU_CLUSTER_PM_ENTER, -1, &nr_calls);
- if (ret)
- /*
- * Inform listeners (nr_calls - 1) about failure of CPU cluster
- * PM entry who are notified earlier to prepare for it.
- */
- cpu_pm_notify(CPU_CLUSTER_PM_ENTER_FAILED, nr_calls - 1, NULL);
-
- return ret;
+ return cpu_pm_notify_enter(CPU_CLUSTER_PM_ENTER, CPU_CLUSTER_ENTER_FAILED);
}
EXPORT_SYMBOL_GPL(cpu_cluster_pm_enter);
@@ -163,7 +156,7 @@ EXPORT_SYMBOL_GPL(cpu_cluster_pm_enter);
*/
int cpu_cluster_pm_exit(void)
{
- return cpu_pm_notify(CPU_CLUSTER_PM_EXIT, -1, NULL);
+ return cpu_pm_notify(CPU_CLUSTER_PM_EXIT);
}
EXPORT_SYMBOL_GPL(cpu_cluster_pm_exit);
--- a/kernel/notifier.c
+++ b/kernel/notifier.c
@@ -106,6 +106,19 @@ static int notifier_call_chain(struct no
}
NOKPROBE_SYMBOL(notifier_call_chain);
+static int notifier_call_chain_error(struct notifier_block **nl,
+ unsigned long val_up, unsigned long val_down,
+ void *v)
+{
+ int ret, nr = 0;
+
+ ret = notifier_call_chain(nl, val_up, v, -1, &nr);
+ if (ret & NOTIFY_STOP_MASK)
+ notifier_call_chain(nl, val_down, v, nr-1, NULL);
+
+ return ret;
+}
+
/*
* Atomic notifier chain routines. Registration and unregistration
* use a spinlock, and call_chain is synchronized by RCU (no locks).
@@ -156,43 +169,30 @@ int atomic_notifier_chain_unregister(str
}
EXPORT_SYMBOL_GPL(atomic_notifier_chain_unregister);
-/**
- * __atomic_notifier_call_chain - Call functions in an atomic notifier chain
- * @nh: Pointer to head of the atomic notifier chain
- * @val: Value passed unmodified to notifier function
- * @v: Pointer passed unmodified to notifier function
- * @nr_to_call: See the comment for notifier_call_chain.
- * @nr_calls: See the comment for notifier_call_chain.
- *
- * Calls each function in a notifier chain in turn. The functions
- * run in an atomic context, so they must not block.
- * This routine uses RCU to synchronize with changes to the chain.
- *
- * If the return value of the notifier can be and'ed
- * with %NOTIFY_STOP_MASK then atomic_notifier_call_chain()
- * will return immediately, with the return value of
- * the notifier function which halted execution.
- * Otherwise the return value is the return value
- * of the last notifier function called.
- */
-int __atomic_notifier_call_chain(struct atomic_notifier_head *nh,
- unsigned long val, void *v,
- int nr_to_call, int *nr_calls)
+int atomic_notifier_call_chain_error(struct atomic_notifier_head *nh,
+ unsigned long val_up, unsigned long val_down, void *v)
{
int ret;
rcu_read_lock();
- ret = notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls);
+ ret = notifier_call_chain_error(&nh->head, val_up, val_down, v);
rcu_read_unlock();
+
return ret;
}
-EXPORT_SYMBOL_GPL(__atomic_notifier_call_chain);
-NOKPROBE_SYMBOL(__atomic_notifier_call_chain);
+EXPORT_SYMBOL_GPL(atomic_notifier_call_chain_error);
+NOKPROBE_SYMBOL(atomic_notifier_call_chain_error);
int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
unsigned long val, void *v)
{
- return __atomic_notifier_call_chain(nh, val, v, -1, NULL);
+ int ret;
+
+ rcu_read_lock();
+ ret = notifier_call_chain(&nh->head, val, v, -1, NULL);
+ rcu_read_unlock();
+
+ return ret;
}
EXPORT_SYMBOL_GPL(atomic_notifier_call_chain);
NOKPROBE_SYMBOL(atomic_notifier_call_chain);
@@ -285,27 +285,8 @@ int blocking_notifier_chain_unregister(s
}
EXPORT_SYMBOL_GPL(blocking_notifier_chain_unregister);
-/**
- * __blocking_notifier_call_chain - Call functions in a blocking notifier chain
- * @nh: Pointer to head of the blocking notifier chain
- * @val: Value passed unmodified to notifier function
- * @v: Pointer passed unmodified to notifier function
- * @nr_to_call: See comment for notifier_call_chain.
- * @nr_calls: See comment for notifier_call_chain.
- *
- * Calls each function in a notifier chain in turn. The functions
- * run in a process context, so they are allowed to block.
- *
- * If the return value of the notifier can be and'ed
- * with %NOTIFY_STOP_MASK then blocking_notifier_call_chain()
- * will return immediately, with the return value of
- * the notifier function which halted execution.
- * Otherwise the return value is the return value
- * of the last notifier function called.
- */
-int __blocking_notifier_call_chain(struct blocking_notifier_head *nh,
- unsigned long val, void *v,
- int nr_to_call, int *nr_calls)
+int blocking_notifier_call_chain_error(struct blocking_notifier_head *nh,
+ unsigned long val_up, unsigned long val_down, void *v)
{
int ret = NOTIFY_DONE;
@@ -316,18 +297,29 @@ int __blocking_notifier_call_chain(struc
*/
if (rcu_access_pointer(nh->head)) {
down_read(&nh->rwsem);
- ret = notifier_call_chain(&nh->head, val, v, nr_to_call,
- nr_calls);
+ ret = notifier_call_chain_error(&nh->head, val_up, val_down, v);
up_read(&nh->rwsem);
}
return ret;
}
-EXPORT_SYMBOL_GPL(__blocking_notifier_call_chain);
+EXPORT_SYMBOL_GPL(blocking_notifier_call_chain_error);
int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
unsigned long val, void *v)
{
- return __blocking_notifier_call_chain(nh, val, v, -1, NULL);
+ int ret = NOTIFY_DONE;
+
+ /*
+ * We check the head outside the lock, but if this access is
+ * racy then it does not matter what the result of the test
+ * is, we re-check the list after having taken the lock anyway:
+ */
+ if (rcu_access_pointer(nh->head)) {
+ down_read(&nh->rwsem);
+ ret = notifier_call_chain(&nh->head, val, v, -1, NULL);
+ up_read(&nh->rwsem);
+ }
+ return ret;
}
EXPORT_SYMBOL_GPL(blocking_notifier_call_chain);
@@ -370,37 +362,17 @@ int raw_notifier_chain_unregister(struct
}
EXPORT_SYMBOL_GPL(raw_notifier_chain_unregister);
-/**
- * __raw_notifier_call_chain - Call functions in a raw notifier chain
- * @nh: Pointer to head of the raw notifier chain
- * @val: Value passed unmodified to notifier function
- * @v: Pointer passed unmodified to notifier function
- * @nr_to_call: See comment for notifier_call_chain.
- * @nr_calls: See comment for notifier_call_chain
- *
- * Calls each function in a notifier chain in turn. The functions
- * run in an undefined context.
- * All locking must be provided by the caller.
- *
- * If the return value of the notifier can be and'ed
- * with %NOTIFY_STOP_MASK then raw_notifier_call_chain()
- * will return immediately, with the return value of
- * the notifier function which halted execution.
- * Otherwise the return value is the return value
- * of the last notifier function called.
- */
-int __raw_notifier_call_chain(struct raw_notifier_head *nh,
- unsigned long val, void *v,
- int nr_to_call, int *nr_calls)
+int raw_notifier_call_chain_error(struct raw_notifier_head *nh,
+ unsigned long val_up, unsigned long val_down, void *v)
{
- return notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls);
+ return notifier_call_chain_error(&nh->head, val_up, val_down, v);
}
-EXPORT_SYMBOL_GPL(__raw_notifier_call_chain);
+EXPORT_SYMBOL_GPL(raw_notifier_call_chain_error);
int raw_notifier_call_chain(struct raw_notifier_head *nh,
unsigned long val, void *v)
{
- return __raw_notifier_call_chain(nh, val, v, -1, NULL);
+ return notifier_call_chain(&nh->head, val, v, -1, NULL);
}
EXPORT_SYMBOL_GPL(raw_notifier_call_chain);
@@ -471,42 +443,29 @@ int srcu_notifier_chain_unregister(struc
}
EXPORT_SYMBOL_GPL(srcu_notifier_chain_unregister);
-/**
- * __srcu_notifier_call_chain - Call functions in an SRCU notifier chain
- * @nh: Pointer to head of the SRCU notifier chain
- * @val: Value passed unmodified to notifier function
- * @v: Pointer passed unmodified to notifier function
- * @nr_to_call: See comment for notifier_call_chain.
- * @nr_calls: See comment for notifier_call_chain
- *
- * Calls each function in a notifier chain in turn. The functions
- * run in a process context, so they are allowed to block.
- *
- * If the return value of the notifier can be and'ed
- * with %NOTIFY_STOP_MASK then srcu_notifier_call_chain()
- * will return immediately, with the return value of
- * the notifier function which halted execution.
- * Otherwise the return value is the return value
- * of the last notifier function called.
- */
-int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
- unsigned long val, void *v,
- int nr_to_call, int *nr_calls)
+int srcu_notifier_call_chain_error(struct srcu_notifier_head *nh,
+ unsigned long val_up, unsigned long val_down, void *v)
{
int ret;
int idx;
idx = srcu_read_lock(&nh->srcu);
- ret = notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls);
+ ret = notifier_call_chain_error(&nh->head, val_up, val_down, v);
srcu_read_unlock(&nh->srcu, idx);
return ret;
}
-EXPORT_SYMBOL_GPL(__srcu_notifier_call_chain);
+EXPORT_SYMBOL_GPL(srcu_notifier_call_chain_error);
int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
unsigned long val, void *v)
{
- return __srcu_notifier_call_chain(nh, val, v, -1, NULL);
+ int ret;
+ int idx;
+
+ idx = srcu_read_lock(&nh->srcu);
+ ret = notifier_call_chain(&nh->head, val, v, -1, NULL);
+ srcu_read_unlock(&nh->srcu, idx);
+ return ret;
}
EXPORT_SYMBOL_GPL(srcu_notifier_call_chain);
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -693,8 +693,8 @@ static int load_image_and_restore(void)
*/
int hibernate(void)
{
- int error, nr_calls = 0;
bool snapshot_test = false;
+ int error;
if (!hibernation_available()) {
pm_pr_dbg("Hibernation not available.\n");
@@ -710,11 +710,9 @@ int hibernate(void)
pr_info("hibernation entry\n");
pm_prepare_console();
- error = __pm_notifier_call_chain(PM_HIBERNATION_PREPARE, -1, &nr_calls);
- if (error) {
- nr_calls--;
- goto Exit;
- }
+ error = pm_notifier_call_chain_error(PM_HIBERNATION_PREPARE, PM_POST_HIBERNATION);
+ if (error)
+ goto Restore;
ksys_sync_helper();
@@ -772,7 +770,8 @@ int hibernate(void)
/* Don't bother checking whether freezer_test_done is true */
freezer_test_done = false;
Exit:
- __pm_notifier_call_chain(PM_POST_HIBERNATION, nr_calls, NULL);
+ pm_notifier_call_chain(PM_POST_HIBERNATION);
+ Restore:
pm_restore_console();
atomic_inc(&snapshot_device_available);
Unlock:
@@ -800,7 +799,7 @@ int hibernate(void)
*/
static int software_resume(void)
{
- int error, nr_calls = 0;
+ int error;
/*
* If the user said "noresume".. bail out early.
@@ -887,11 +886,9 @@ static int software_resume(void)
pr_info("resume from hibernation\n");
pm_prepare_console();
- error = __pm_notifier_call_chain(PM_RESTORE_PREPARE, -1, &nr_calls);
- if (error) {
- nr_calls--;
- goto Close_Finish;
- }
+ error = pm_notifier_call_chain_error(PM_RESTORE_PREPARE, PM_POST_RESTORE);
+ if (error)
+ goto Restore;
pm_pr_dbg("Preparing processes for restore.\n");
error = freeze_processes();
@@ -900,7 +897,8 @@ static int software_resume(void)
error = load_image_and_restore();
thaw_processes();
Finish:
- __pm_notifier_call_chain(PM_POST_RESTORE, nr_calls, NULL);
+ pm_notifier_call_chain(PM_POST_RESTORE);
+ Restore:
pm_restore_console();
pr_info("resume from hibernation failed (%d)\n", error);
atomic_inc(&snapshot_device_available);
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -79,18 +79,18 @@ int unregister_pm_notifier(struct notifi
}
EXPORT_SYMBOL_GPL(unregister_pm_notifier);
-int __pm_notifier_call_chain(unsigned long val, int nr_to_call, int *nr_calls)
+int pm_notifier_call_chain_error(unsigned long val_up, unsigned long val_down)
{
int ret;
- ret = __blocking_notifier_call_chain(&pm_chain_head, val, NULL,
- nr_to_call, nr_calls);
+ ret = blocking_notifier_call_chain_error(&pm_chain_head, val_up, val_down, NULL);
return notifier_to_errno(ret);
}
+
int pm_notifier_call_chain(unsigned long val)
{
- return __pm_notifier_call_chain(val, -1, NULL);
+ return blocking_notifier_call_chain(&pm_chain_head, val, NULL);
}
/* If set, devices may be suspended and resumed asynchronously. */
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -212,8 +212,7 @@ static inline void suspend_test_finish(c
#ifdef CONFIG_PM_SLEEP
/* kernel/power/main.c */
-extern int __pm_notifier_call_chain(unsigned long val, int nr_to_call,
- int *nr_calls);
+extern int pm_notifier_call_chain_error(unsigned long val_up, unsigned long val_down);
extern int pm_notifier_call_chain(unsigned long val);
#endif
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -352,18 +352,16 @@ static int suspend_test(int level)
*/
static int suspend_prepare(suspend_state_t state)
{
- int error, nr_calls = 0;
+ int error;
if (!sleep_state_supported(state))
return -EPERM;
pm_prepare_console();
- error = __pm_notifier_call_chain(PM_SUSPEND_PREPARE, -1, &nr_calls);
- if (error) {
- nr_calls--;
- goto Finish;
- }
+ error = pm_notifier_call_chain_error(PM_SUSPEND_PREPARE, PM_POST_SUSPEND);
+ if (error)
+ goto Restore;
trace_suspend_resume(TPS("freeze_processes"), 0, true);
error = suspend_freeze_processes();
@@ -373,8 +371,8 @@ static int suspend_prepare(suspend_state
suspend_stats.failed_freeze++;
dpm_save_failed_step(SUSPEND_FREEZE);
- Finish:
- __pm_notifier_call_chain(PM_POST_SUSPEND, nr_calls, NULL);
+ pm_notifier_call_chain(PM_POST_SUSPEND);
+ Restore:
pm_restore_console();
return error;
}
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -44,7 +44,7 @@ atomic_t snapshot_device_available = ATO
static int snapshot_open(struct inode *inode, struct file *filp)
{
struct snapshot_data *data;
- int error, nr_calls = 0;
+ int error;
if (!hibernation_available())
return -EPERM;
@@ -71,9 +71,7 @@ static int snapshot_open(struct inode *i
swap_type_of(swsusp_resume_device, 0, NULL) : -1;
data->mode = O_RDONLY;
data->free_bitmaps = false;
- error = __pm_notifier_call_chain(PM_HIBERNATION_PREPARE, -1, &nr_calls);
- if (error)
- __pm_notifier_call_chain(PM_POST_HIBERNATION, --nr_calls, NULL);
+ error = pm_notifier_call_chain_error(PM_HIBERNATION_PREPARE, PM_POST_HIBERNATION);
} else {
/*
* Resuming. We may need to wait for the image device to
@@ -83,15 +81,11 @@ static int snapshot_open(struct inode *i
data->swap = -1;
data->mode = O_WRONLY;
- error = __pm_notifier_call_chain(PM_RESTORE_PREPARE, -1, &nr_calls);
+ error = pm_notifier_call_chain_error(PM_RESTORE_PREPARE, PM_POST_RESTORE);
if (!error) {
error = create_basic_memory_bitmaps();
data->free_bitmaps = !error;
- } else
- nr_calls--;
-
- if (error)
- __pm_notifier_call_chain(PM_POST_RESTORE, nr_calls, NULL);
+ }
}
if (error)
atomic_inc(&snapshot_device_available);
--- a/tools/power/pm-graph/sleepgraph.py
+++ b/tools/power/pm-graph/sleepgraph.py
@@ -146,7 +146,7 @@ from subprocess import call, Popen, PIPE
tracefuncs = {
'sys_sync': {},
'ksys_sync': {},
- '__pm_notifier_call_chain': {},
+ 'pm_notifier_call_chain_error': {},
'pm_prepare_console': {},
'pm_notifier_call_chain': {},
'freeze_processes': {},
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH 1/3] notifier: Fix broken error handling pattern
2019-06-24 9:18 ` [PATCH 1/3] notifier: Fix broken error handling pattern Peter Zijlstra
@ 2019-06-24 22:21 ` Josh Poimboeuf
2019-06-25 7:38 ` Peter Zijlstra
0 siblings, 1 reply; 5+ messages in thread
From: Josh Poimboeuf @ 2019-06-24 22:21 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Jessica Yu, linux-kernel, jikos, mbenes, pmladek, ast, daniel,
akpm, Rafael J. Wysocki, Pavel Machek, Len Brown, Sam Protsenko,
Thomas Gleixner, Greg Kroah-Hartman, Alexios Zavras,
Allison Randal, Vasily Averin, Todd Brandt, linux-pm
On Mon, Jun 24, 2019 at 11:18:44AM +0200, Peter Zijlstra wrote:
> The current notifiers have the following error handling pattern all
> over the place:
>
> int nr;
>
> ret = __foo_notifier_call_chain(&chain, val_up, v, -1, &nr);
> if (err & NOTIFIER_STOP_MASK)
s/err/ret/
> __foo_notifier_call_chain(&chain, val_down, v, nr-1, NULL)
>
> And aside from the endless repetition thereof, it is broken. Consider
> blocking notifiers; both calls take and drop the rwsem, this means
> that the notifier list can change in between the two calls, making @nr
> meaningless.
>
> Fix this by replacing all the __foo_notifier_call_chain() functions
> with foo_notifier_call_chain_error() that embeds the above patter, but
> ensures it is inside a single lock region.
The name "notifier_call_chain_error()" seems confusing, it almost sounds
like it's notifying an error code. Then again, I can't really think of
a more reasonably succinct name.
> @@ -25,8 +25,23 @@ static int cpu_pm_notify(enum cpu_pm_eve
> * RCU know this.
> */
> rcu_irq_enter_irqson();
> - ret = __atomic_notifier_call_chain(&cpu_pm_notifier_chain, event, NULL,
> - nr_to_call, nr_calls);
> + ret = atomic_notifier_call_chain(&cpu_pm_notifier_chain, event, NULL);
> + rcu_irq_exit_irqson();
> +
> + return notifier_to_errno(ret);
> +}
> +
> +static int cpu_pm_notify_error(enum cpu_pm_event event_up, enum cpu_pm_event event_down)
> +{
> + int ret;
> +
> + /*
> + * __atomic_notifier_call_chain has a RCU read critical section, which
__atomic_notifier_call_chain() no longer exists.
> + * could be disfunctional in cpu idle. Copy RCU_NONIDLE code to let
"dysfunctional"
> @@ -156,43 +169,30 @@ int atomic_notifier_chain_unregister(str
> }
> EXPORT_SYMBOL_GPL(atomic_notifier_chain_unregister);
>
> -/**
> - * __atomic_notifier_call_chain - Call functions in an atomic notifier chain
> - * @nh: Pointer to head of the atomic notifier chain
> - * @val: Value passed unmodified to notifier function
> - * @v: Pointer passed unmodified to notifier function
> - * @nr_to_call: See the comment for notifier_call_chain.
> - * @nr_calls: See the comment for notifier_call_chain.
> - *
> - * Calls each function in a notifier chain in turn. The functions
> - * run in an atomic context, so they must not block.
> - * This routine uses RCU to synchronize with changes to the chain.
> - *
> - * If the return value of the notifier can be and'ed
> - * with %NOTIFY_STOP_MASK then atomic_notifier_call_chain()
> - * will return immediately, with the return value of
> - * the notifier function which halted execution.
> - * Otherwise the return value is the return value
> - * of the last notifier function called.
> - */
Why remove the useful comment?
Ditto for the blocking, raw, srcu, comments.
--
Josh
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH 1/3] notifier: Fix broken error handling pattern
2019-06-24 22:21 ` Josh Poimboeuf
@ 2019-06-25 7:38 ` Peter Zijlstra
2019-06-25 12:13 ` Josh Poimboeuf
0 siblings, 1 reply; 5+ messages in thread
From: Peter Zijlstra @ 2019-06-25 7:38 UTC (permalink / raw)
To: Josh Poimboeuf
Cc: Jessica Yu, linux-kernel, jikos, mbenes, pmladek, ast, daniel,
akpm, Rafael J. Wysocki, Pavel Machek, Len Brown, Sam Protsenko,
Thomas Gleixner, Greg Kroah-Hartman, Alexios Zavras,
Allison Randal, Vasily Averin, Todd Brandt, linux-pm
On Mon, Jun 24, 2019 at 05:21:07PM -0500, Josh Poimboeuf wrote:
> On Mon, Jun 24, 2019 at 11:18:44AM +0200, Peter Zijlstra wrote:
> > The current notifiers have the following error handling pattern all
> > over the place:
> >
> > int nr;
> >
> > ret = __foo_notifier_call_chain(&chain, val_up, v, -1, &nr);
> > if (err & NOTIFIER_STOP_MASK)
>
> s/err/ret/
-ETOOWARM :-)
> > __foo_notifier_call_chain(&chain, val_down, v, nr-1, NULL)
> >
> > And aside from the endless repetition thereof, it is broken. Consider
> > blocking notifiers; both calls take and drop the rwsem, this means
> > that the notifier list can change in between the two calls, making @nr
> > meaningless.
> >
> > Fix this by replacing all the __foo_notifier_call_chain() functions
> > with foo_notifier_call_chain_error() that embeds the above patter, but
> > ensures it is inside a single lock region.
>
> The name "notifier_call_chain_error()" seems confusing, it almost sounds
> like it's notifying an error code. Then again, I can't really think of
> a more reasonably succinct name.
I;m not attached to the name; I very much ran out of ideas and just
typed something.
> > @@ -25,8 +25,23 @@ static int cpu_pm_notify(enum cpu_pm_eve
> > * RCU know this.
> > */
> > rcu_irq_enter_irqson();
> > - ret = __atomic_notifier_call_chain(&cpu_pm_notifier_chain, event, NULL,
> > - nr_to_call, nr_calls);
> > + ret = atomic_notifier_call_chain(&cpu_pm_notifier_chain, event, NULL);
> > + rcu_irq_exit_irqson();
> > +
> > + return notifier_to_errno(ret);
> > +}
> > +
> > +static int cpu_pm_notify_error(enum cpu_pm_event event_up, enum cpu_pm_event event_down)
> > +{
> > + int ret;
> > +
> > + /*
> > + * __atomic_notifier_call_chain has a RCU read critical section, which
>
> __atomic_notifier_call_chain() no longer exists.
>
> > + * could be disfunctional in cpu idle. Copy RCU_NONIDLE code to let
>
> "dysfunctional"
That's copy paste, I don't think I've read the comment, my bad.
> > @@ -156,43 +169,30 @@ int atomic_notifier_chain_unregister(str
> > }
> > EXPORT_SYMBOL_GPL(atomic_notifier_chain_unregister);
> >
> > -/**
> > - * __atomic_notifier_call_chain - Call functions in an atomic notifier chain
> > - * @nh: Pointer to head of the atomic notifier chain
> > - * @val: Value passed unmodified to notifier function
> > - * @v: Pointer passed unmodified to notifier function
> > - * @nr_to_call: See the comment for notifier_call_chain.
> > - * @nr_calls: See the comment for notifier_call_chain.
> > - *
> > - * Calls each function in a notifier chain in turn. The functions
> > - * run in an atomic context, so they must not block.
> > - * This routine uses RCU to synchronize with changes to the chain.
> > - *
> > - * If the return value of the notifier can be and'ed
> > - * with %NOTIFY_STOP_MASK then atomic_notifier_call_chain()
> > - * will return immediately, with the return value of
> > - * the notifier function which halted execution.
> > - * Otherwise the return value is the return value
> > - * of the last notifier function called.
> > - */
>
> Why remove the useful comment?
Because I delete the whole function ?
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH 1/3] notifier: Fix broken error handling pattern
2019-06-25 7:38 ` Peter Zijlstra
@ 2019-06-25 12:13 ` Josh Poimboeuf
2019-06-25 13:22 ` Peter Zijlstra
0 siblings, 1 reply; 5+ messages in thread
From: Josh Poimboeuf @ 2019-06-25 12:13 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Jessica Yu, linux-kernel, jikos, mbenes, pmladek, ast, daniel,
akpm, Rafael J. Wysocki, Pavel Machek, Len Brown, Sam Protsenko,
Thomas Gleixner, Greg Kroah-Hartman, Alexios Zavras,
Allison Randal, Vasily Averin, Todd Brandt, linux-pm
On Tue, Jun 25, 2019 at 09:38:21AM +0200, Peter Zijlstra wrote:
> > > @@ -156,43 +169,30 @@ int atomic_notifier_chain_unregister(str
> > > }
> > > EXPORT_SYMBOL_GPL(atomic_notifier_chain_unregister);
> > >
> > > -/**
> > > - * __atomic_notifier_call_chain - Call functions in an atomic notifier chain
> > > - * @nh: Pointer to head of the atomic notifier chain
> > > - * @val: Value passed unmodified to notifier function
> > > - * @v: Pointer passed unmodified to notifier function
> > > - * @nr_to_call: See the comment for notifier_call_chain.
> > > - * @nr_calls: See the comment for notifier_call_chain.
> > > - *
> > > - * Calls each function in a notifier chain in turn. The functions
> > > - * run in an atomic context, so they must not block.
> > > - * This routine uses RCU to synchronize with changes to the chain.
> > > - *
> > > - * If the return value of the notifier can be and'ed
> > > - * with %NOTIFY_STOP_MASK then atomic_notifier_call_chain()
> > > - * will return immediately, with the return value of
> > > - * the notifier function which halted execution.
> > > - * Otherwise the return value is the return value
> > > - * of the last notifier function called.
> > > - */
> >
> > Why remove the useful comment?
>
> Because I delete the whole function ?
I viewed it as more of a rename... Regardless would the comment not
still be useful for the non-double-underscore version of the function?
--
Josh
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH 1/3] notifier: Fix broken error handling pattern
2019-06-25 12:13 ` Josh Poimboeuf
@ 2019-06-25 13:22 ` Peter Zijlstra
0 siblings, 0 replies; 5+ messages in thread
From: Peter Zijlstra @ 2019-06-25 13:22 UTC (permalink / raw)
To: Josh Poimboeuf
Cc: Jessica Yu, linux-kernel, jikos, mbenes, pmladek, ast, daniel,
akpm, Rafael J. Wysocki, Pavel Machek, Len Brown, Sam Protsenko,
Thomas Gleixner, Greg Kroah-Hartman, Alexios Zavras,
Allison Randal, Vasily Averin, Todd Brandt, linux-pm
On Tue, Jun 25, 2019 at 07:13:34AM -0500, Josh Poimboeuf wrote:
> On Tue, Jun 25, 2019 at 09:38:21AM +0200, Peter Zijlstra wrote:
> > > > @@ -156,43 +169,30 @@ int atomic_notifier_chain_unregister(str
> > > > }
> > > > EXPORT_SYMBOL_GPL(atomic_notifier_chain_unregister);
> > > >
> > > > -/**
> > > > - * __atomic_notifier_call_chain - Call functions in an atomic notifier chain
> > > > - * @nh: Pointer to head of the atomic notifier chain
> > > > - * @val: Value passed unmodified to notifier function
> > > > - * @v: Pointer passed unmodified to notifier function
> > > > - * @nr_to_call: See the comment for notifier_call_chain.
> > > > - * @nr_calls: See the comment for notifier_call_chain.
> > > > - *
> > > > - * Calls each function in a notifier chain in turn. The functions
> > > > - * run in an atomic context, so they must not block.
> > > > - * This routine uses RCU to synchronize with changes to the chain.
> > > > - *
> > > > - * If the return value of the notifier can be and'ed
> > > > - * with %NOTIFY_STOP_MASK then atomic_notifier_call_chain()
> > > > - * will return immediately, with the return value of
> > > > - * the notifier function which halted execution.
> > > > - * Otherwise the return value is the return value
> > > > - * of the last notifier function called.
> > > > - */
> > >
> > > Why remove the useful comment?
> >
> > Because I delete the whole function ?
>
> I viewed it as more of a rename... Regardless would the comment not
> still be useful for the non-double-underscore version of the function?
I never got that far, I just deleted the whole thing without reading it.
But yes, with a few tweaks it should apply to the normal function.
^ permalink raw reply [flat|nested] 5+ messages in thread
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2019-06-24 9:18 ` [PATCH 1/3] notifier: Fix broken error handling pattern Peter Zijlstra
2019-06-24 22:21 ` Josh Poimboeuf
2019-06-25 7:38 ` Peter Zijlstra
2019-06-25 12:13 ` Josh Poimboeuf
2019-06-25 13:22 ` Peter Zijlstra
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