* [PATCH] locking/lockdep: Dump state of percpu_rwsem upon hung up.
@ 2018-07-07 6:31 Tetsuo Handa
2018-07-07 11:31 ` kbuild test robot
2018-07-10 11:47 ` [PATCH v2] locking/lockdep: Dump state of percpu_rwsem upon hung up Tetsuo Handa
0 siblings, 2 replies; 11+ messages in thread
From: Tetsuo Handa @ 2018-07-07 6:31 UTC (permalink / raw)
To: akpm
Cc: linux-kernel, Tetsuo Handa, Dmitry Vyukov, Ingo Molnar,
Peter Zijlstra, Will Deacon
This is a temporary patch which should not go to linux.git.
syzbot is hitting hung task problems at __sb_start_write() [1]. While hung
tasks at __sb_start_write() suggest that filesystem was frozen, syzbot is
not doing ioctl(FIFREEZE) requests. Therefore, the root cause of hung tasks
is currently unknown. As a first step for debugging this problem, let's
check what atomic_long_read(&sem->rw_sem.count) says when hung task is
reported. Since it is impossible to reproduce this problem locally, this
patch was made in order to test linux-next.git using syzbot infrastructure.
[1] https://syzkaller.appspot.com/bug?id=287aa8708bc940d0ca1645223c53dd4c2d203be6
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
---
include/linux/sched.h | 1 +
kernel/hung_task.c | 25 +++++++++++++++++++++++++
kernel/locking/percpu-rwsem.c | 2 ++
3 files changed, 28 insertions(+)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index cf1edc0..2aaaf49 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1183,6 +1183,7 @@ struct task_struct {
/* Used by LSM modules for access restriction: */
void *security;
#endif
+ struct percpu_rw_semaphore *pcpu_rwsem_read_waiting;
#ifdef CONFIG_GCC_PLUGIN_STACKLEAK
unsigned long lowest_stack;
diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index b9132d1..03d7d9b 100644
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -18,6 +18,7 @@
#include <linux/utsname.h>
#include <linux/sched/signal.h>
#include <linux/sched/debug.h>
+#include <linux/percpu-rwsem.h>
#include <trace/events/sched.h>
@@ -82,6 +83,29 @@ static int __init hung_task_panic_setup(char *str)
.notifier_call = hung_task_panic,
};
+static void dump_percpu_rwsem_state(struct percpu_rw_semaphore *sem)
+{
+ unsigned int sum = 0;
+ int cpu;
+
+ if (!sem)
+ return;
+ pr_info("percpu_rw_semaphore(%p)\n", sem);
+ pr_info(" ->rw_sem.count=0x%lx\n",
+ atomic_long_read(&sem->rw_sem.count));
+ pr_info(" ->rss.gp_state=%d\n", sem->rss.gp_state);
+ pr_info(" ->rss.gp_count=%d\n", sem->rss.gp_count);
+ pr_info(" ->rss.cb_state=%d\n", sem->rss.cb_state);
+ pr_info(" ->rss.gp_type=%d\n", sem->rss.gp_type);
+ pr_info(" ->readers_block=%d\n", sem->readers_block);
+ for_each_possible_cpu(cpu)
+ sum += per_cpu(*sem->read_count, cpu);
+ pr_info(" ->read_count=%d\n", sum);
+ pr_info(" ->list_empty(rw_sem.wait_list)=%d\n",
+ list_empty(&sem->rw_sem.wait_list));
+ pr_info(" ->writer.task=%p\n", sem->writer.task);
+}
+
static void check_hung_task(struct task_struct *t, unsigned long timeout)
{
unsigned long switch_count = t->nvcsw + t->nivcsw;
@@ -130,6 +154,7 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
pr_err("\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\""
" disables this message.\n");
sched_show_task(t);
+ dump_percpu_rwsem_state(t->pcpu_rwsem_read_waiting);
hung_task_show_lock = true;
}
diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c
index 883cf1b..b3654ab 100644
--- a/kernel/locking/percpu-rwsem.c
+++ b/kernel/locking/percpu-rwsem.c
@@ -82,7 +82,9 @@ int __percpu_down_read(struct percpu_rw_semaphore *sem, int try)
/*
* Avoid lockdep for the down/up_read() we already have them.
*/
+ current->pcpu_rwsem_read_waiting = sem;
__down_read(&sem->rw_sem);
+ current->pcpu_rwsem_read_waiting = NULL;
this_cpu_inc(*sem->read_count);
__up_read(&sem->rw_sem);
--
1.8.3.1
^ permalink raw reply related [flat|nested] 11+ messages in thread* Re: [PATCH] locking/lockdep: Dump state of percpu_rwsem upon hung up.
2018-07-07 6:31 [PATCH] locking/lockdep: Dump state of percpu_rwsem upon hung up Tetsuo Handa
@ 2018-07-07 11:31 ` kbuild test robot
2018-07-07 14:09 ` Tetsuo Handa
2018-07-10 6:10 ` Tetsuo Handa
2018-07-10 11:47 ` [PATCH v2] locking/lockdep: Dump state of percpu_rwsem upon hung up Tetsuo Handa
1 sibling, 2 replies; 11+ messages in thread
From: kbuild test robot @ 2018-07-07 11:31 UTC (permalink / raw)
To: Tetsuo Handa
Cc: kbuild-all, akpm, linux-kernel, Tetsuo Handa, Dmitry Vyukov,
Ingo Molnar, Peter Zijlstra, Will Deacon
[-- Attachment #1: Type: text/plain, Size: 6382 bytes --]
Hi Tetsuo,
I love your patch! Yet something to improve:
[auto build test ERROR on next-20180706]
[also build test ERROR on v4.18-rc3]
[cannot apply to tip/auto-latest tip/sched/core linus/master v4.18-rc3 v4.18-rc2 v4.18-rc1]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
url: https://github.com/0day-ci/linux/commits/Tetsuo-Handa/locking-lockdep-Dump-state-of-percpu_rwsem-upon-hung-up/20180707-143406
config: mips-allmodconfig (attached as .config)
compiler: mips-linux-gnu-gcc (Debian 7.2.0-11) 7.2.0
reproduce:
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# save the attached .config to linux build tree
GCC_VERSION=7.2.0 make.cross ARCH=mips
All error/warnings (new ones prefixed by >>):
In file included from include/linux/kernel.h:14:0,
from include/asm-generic/bug.h:18,
from arch/mips/include/asm/bug.h:42,
from include/linux/bug.h:5,
from include/linux/mmdebug.h:5,
from include/linux/mm.h:9,
from kernel/hung_task.c:8:
kernel/hung_task.c: In function 'dump_percpu_rwsem_state':
>> kernel/hung_task.c:95:20: error: passing argument 1 of 'atomic_long_read' from incompatible pointer type [-Werror=incompatible-pointer-types]
atomic_long_read(&sem->rw_sem.count));
^
include/linux/printk.h:311:34: note: in definition of macro 'pr_info'
printk(KERN_INFO pr_fmt(fmt), ##__VA_ARGS__)
^~~~~~~~~~~
In file included from include/linux/atomic.h:1309:0,
from arch/mips/include/asm/processor.h:14,
from arch/mips/include/asm/thread_info.h:16,
from include/linux/thread_info.h:38,
from include/asm-generic/preempt.h:5,
from ./arch/mips/include/generated/asm/preempt.h:1,
from include/linux/preempt.h:81,
from include/linux/spinlock.h:51,
from include/linux/mmzone.h:8,
from include/linux/gfp.h:6,
from include/linux/mm.h:10,
from kernel/hung_task.c:8:
include/asm-generic/atomic-long.h:41:20: note: expected 'const atomic_long_t * {aka const struct <anonymous> *}' but argument is of type '__s32 * {aka int *}'
static inline long atomic_long_read##mo(const atomic_long_t *l) \
^
>> include/asm-generic/atomic-long.h:47:1: note: in expansion of macro 'ATOMIC_LONG_READ_OP'
ATOMIC_LONG_READ_OP()
^~~~~~~~~~~~~~~~~~~
cc1: some warnings being treated as errors
vim +/atomic_long_read +95 kernel/hung_task.c
> 8 #include <linux/mm.h>
9 #include <linux/cpu.h>
10 #include <linux/nmi.h>
11 #include <linux/init.h>
12 #include <linux/delay.h>
13 #include <linux/freezer.h>
14 #include <linux/kthread.h>
15 #include <linux/lockdep.h>
16 #include <linux/export.h>
17 #include <linux/sysctl.h>
18 #include <linux/utsname.h>
19 #include <linux/sched/signal.h>
20 #include <linux/sched/debug.h>
21 #include <linux/percpu-rwsem.h>
22
23 #include <trace/events/sched.h>
24
25 /*
26 * The number of tasks checked:
27 */
28 int __read_mostly sysctl_hung_task_check_count = PID_MAX_LIMIT;
29
30 /*
31 * Limit number of tasks checked in a batch.
32 *
33 * This value controls the preemptibility of khungtaskd since preemption
34 * is disabled during the critical section. It also controls the size of
35 * the RCU grace period. So it needs to be upper-bound.
36 */
37 #define HUNG_TASK_BATCHING 1024
38
39 /*
40 * Zero means infinite timeout - no checking done:
41 */
42 unsigned long __read_mostly sysctl_hung_task_timeout_secs = CONFIG_DEFAULT_HUNG_TASK_TIMEOUT;
43
44 /*
45 * Zero (default value) means use sysctl_hung_task_timeout_secs:
46 */
47 unsigned long __read_mostly sysctl_hung_task_check_interval_secs;
48
49 int __read_mostly sysctl_hung_task_warnings = 10;
50
51 static int __read_mostly did_panic;
52 static bool hung_task_show_lock;
53 static bool hung_task_call_panic;
54
55 static struct task_struct *watchdog_task;
56
57 /*
58 * Should we panic (and reboot, if panic_timeout= is set) when a
59 * hung task is detected:
60 */
61 unsigned int __read_mostly sysctl_hung_task_panic =
62 CONFIG_BOOTPARAM_HUNG_TASK_PANIC_VALUE;
63
64 static int __init hung_task_panic_setup(char *str)
65 {
66 int rc = kstrtouint(str, 0, &sysctl_hung_task_panic);
67
68 if (rc)
69 return rc;
70 return 1;
71 }
72 __setup("hung_task_panic=", hung_task_panic_setup);
73
74 static int
75 hung_task_panic(struct notifier_block *this, unsigned long event, void *ptr)
76 {
77 did_panic = 1;
78
79 return NOTIFY_DONE;
80 }
81
82 static struct notifier_block panic_block = {
83 .notifier_call = hung_task_panic,
84 };
85
86 static void dump_percpu_rwsem_state(struct percpu_rw_semaphore *sem)
87 {
88 unsigned int sum = 0;
89 int cpu;
90
91 if (!sem)
92 return;
93 pr_info("percpu_rw_semaphore(%p)\n", sem);
94 pr_info(" ->rw_sem.count=0x%lx\n",
> 95 atomic_long_read(&sem->rw_sem.count));
96 pr_info(" ->rss.gp_state=%d\n", sem->rss.gp_state);
97 pr_info(" ->rss.gp_count=%d\n", sem->rss.gp_count);
98 pr_info(" ->rss.cb_state=%d\n", sem->rss.cb_state);
99 pr_info(" ->rss.gp_type=%d\n", sem->rss.gp_type);
100 pr_info(" ->readers_block=%d\n", sem->readers_block);
101 for_each_possible_cpu(cpu)
102 sum += per_cpu(*sem->read_count, cpu);
103 pr_info(" ->read_count=%d\n", sum);
104 pr_info(" ->list_empty(rw_sem.wait_list)=%d\n",
105 list_empty(&sem->rw_sem.wait_list));
106 pr_info(" ->writer.task=%p\n", sem->writer.task);
107 }
108
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 56614 bytes --]
^ permalink raw reply [flat|nested] 11+ messages in thread* Re: [PATCH] locking/lockdep: Dump state of percpu_rwsem upon hung up.
2018-07-07 11:31 ` kbuild test robot
@ 2018-07-07 14:09 ` Tetsuo Handa
2018-07-10 6:10 ` Tetsuo Handa
1 sibling, 0 replies; 11+ messages in thread
From: Tetsuo Handa @ 2018-07-07 14:09 UTC (permalink / raw)
To: kbuild test robot
Cc: kbuild-all, akpm, linux-kernel, Dmitry Vyukov, Ingo Molnar,
Peter Zijlstra, Will Deacon
Hello.
Thanks for doing build test, but I don't understand what is wrong.
As far as I can see, "struct percpu_rw_semaphore" contains "struct rw_semaphore"
and "struct rw_semaphore" contains "atomic_long_t count".
Then, why trying to read using atomic_long_read(&sem->rw_sem.count) causes
note: expected 'const atomic_long_t * {aka const struct <anonymous> *}' but argument is of type '__s32 * {aka int *}'
warning? Is mips using different type?
struct percpu_rw_semaphore {
struct rcu_sync rss;
unsigned int __percpu *read_count;
struct rw_semaphore rw_sem; /* slowpath */
struct rcuwait writer; /* blocked writer */
int readers_block;
};
/* All arch specific implementations share the same struct */
struct rw_semaphore {
atomic_long_t count;
struct list_head wait_list;
raw_spinlock_t wait_lock;
#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
struct optimistic_spin_queue osq; /* spinner MCS lock */
/*
* Write owner. Used as a speculative check to see
* if the owner is running on the cpu.
*/
struct task_struct *owner;
#endif
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lockdep_map dep_map;
#endif
};
On 2018/07/07 20:31, kbuild test robot wrote:
> Hi Tetsuo,
>
> I love your patch! Yet something to improve:
>
> [auto build test ERROR on next-20180706]
> [also build test ERROR on v4.18-rc3]
> [cannot apply to tip/auto-latest tip/sched/core linus/master v4.18-rc3 v4.18-rc2 v4.18-rc1]
> [if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
>
> url: https://github.com/0day-ci/linux/commits/Tetsuo-Handa/locking-lockdep-Dump-state-of-percpu_rwsem-upon-hung-up/20180707-143406
> config: mips-allmodconfig (attached as .config)
> compiler: mips-linux-gnu-gcc (Debian 7.2.0-11) 7.2.0
> reproduce:
> wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> chmod +x ~/bin/make.cross
> # save the attached .config to linux build tree
> GCC_VERSION=7.2.0 make.cross ARCH=mips
>
> All error/warnings (new ones prefixed by >>):
>
> In file included from include/linux/kernel.h:14:0,
> from include/asm-generic/bug.h:18,
> from arch/mips/include/asm/bug.h:42,
> from include/linux/bug.h:5,
> from include/linux/mmdebug.h:5,
> from include/linux/mm.h:9,
> from kernel/hung_task.c:8:
> kernel/hung_task.c: In function 'dump_percpu_rwsem_state':
>>> kernel/hung_task.c:95:20: error: passing argument 1 of 'atomic_long_read' from incompatible pointer type [-Werror=incompatible-pointer-types]
> atomic_long_read(&sem->rw_sem.count));
> ^
> include/linux/printk.h:311:34: note: in definition of macro 'pr_info'
> printk(KERN_INFO pr_fmt(fmt), ##__VA_ARGS__)
> ^~~~~~~~~~~
> In file included from include/linux/atomic.h:1309:0,
> from arch/mips/include/asm/processor.h:14,
> from arch/mips/include/asm/thread_info.h:16,
> from include/linux/thread_info.h:38,
> from include/asm-generic/preempt.h:5,
> from ./arch/mips/include/generated/asm/preempt.h:1,
> from include/linux/preempt.h:81,
> from include/linux/spinlock.h:51,
> from include/linux/mmzone.h:8,
> from include/linux/gfp.h:6,
> from include/linux/mm.h:10,
> from kernel/hung_task.c:8:
> include/asm-generic/atomic-long.h:41:20: note: expected 'const atomic_long_t * {aka const struct <anonymous> *}' but argument is of type '__s32 * {aka int *}'
> static inline long atomic_long_read##mo(const atomic_long_t *l) \
> ^
>>> include/asm-generic/atomic-long.h:47:1: note: in expansion of macro 'ATOMIC_LONG_READ_OP'
> ATOMIC_LONG_READ_OP()
> ^~~~~~~~~~~~~~~~~~~
> cc1: some warnings being treated as errors
^ permalink raw reply [flat|nested] 11+ messages in thread* Re: [PATCH] locking/lockdep: Dump state of percpu_rwsem upon hung up.
2018-07-07 11:31 ` kbuild test robot
2018-07-07 14:09 ` Tetsuo Handa
@ 2018-07-10 6:10 ` Tetsuo Handa
2018-07-10 9:20 ` Will Deacon
` (3 more replies)
1 sibling, 4 replies; 11+ messages in thread
From: Tetsuo Handa @ 2018-07-10 6:10 UTC (permalink / raw)
To: kbuild test robot
Cc: kbuild-all, akpm, linux-kernel, Dmitry Vyukov, Ingo Molnar,
Peter Zijlstra, Will Deacon
From 2642b4a1904259384f2018ea8df03ac49509c57a Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@I-love.SKAURA.ne.jp>
Date: Tue, 10 Jul 2018 15:01:20 +0900
Subject: [PATCH] locking/rwsem: Convert the other sem->count to 'atomic_long_t'
Since "locking/rwsem: Convert sem->count to 'atomic_long_t'" forgot to
convert "struct rw_semaphore"->count in linux/rwsem-spinlock.h which is
used when CONFIG_RWSEM_GENERIC_SPINLOCK=y, trying to access it in MIPS
architecture causes build error due to type mismatch.
error: passing argument 1 of 'atomic_long_read' from incompatible pointer type [-Werror=incompatible-pointer-types]
note: expected 'const atomic_long_t * {aka const struct <anonymous> *}' but argument is of type '__s32 * {aka int *}'
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SKAURA.ne.jp>
Reported-by: kbuild test robot <lkp@intel.com>
Fixes: 8ee62b1870be8e63 ("locking/rwsem: Convert sem->count to 'atomic_long_t'")
Cc: stable <stable@vger.kernel.org> # v4.8+
Cc: Jason Low <jason.low2@hpe.com>
Cc: Peter Zijlstra <peterz@infradead.org>
---
include/linux/rwsem-spinlock.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/rwsem-spinlock.h b/include/linux/rwsem-spinlock.h
index e475683..1164965 100644
--- a/include/linux/rwsem-spinlock.h
+++ b/include/linux/rwsem-spinlock.h
@@ -22,7 +22,7 @@
* - if wait_list is not empty, then there are processes waiting for the semaphore
*/
struct rw_semaphore {
- __s32 count;
+ atomic_long_t count;
raw_spinlock_t wait_lock;
struct list_head wait_list;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
--
2.7.4
^ permalink raw reply related [flat|nested] 11+ messages in thread* Re: [PATCH] locking/lockdep: Dump state of percpu_rwsem upon hung up.
2018-07-10 6:10 ` Tetsuo Handa
@ 2018-07-10 9:20 ` Will Deacon
2018-07-10 9:30 ` Peter Zijlstra
` (2 subsequent siblings)
3 siblings, 0 replies; 11+ messages in thread
From: Will Deacon @ 2018-07-10 9:20 UTC (permalink / raw)
To: Tetsuo Handa
Cc: kbuild test robot, kbuild-all, akpm, linux-kernel, Dmitry Vyukov,
Ingo Molnar, Peter Zijlstra
On Tue, Jul 10, 2018 at 03:10:51PM +0900, Tetsuo Handa wrote:
> From 2642b4a1904259384f2018ea8df03ac49509c57a Mon Sep 17 00:00:00 2001
> From: Tetsuo Handa <penguin-kernel@I-love.SKAURA.ne.jp>
> Date: Tue, 10 Jul 2018 15:01:20 +0900
> Subject: [PATCH] locking/rwsem: Convert the other sem->count to 'atomic_long_t'
>
> Since "locking/rwsem: Convert sem->count to 'atomic_long_t'" forgot to
> convert "struct rw_semaphore"->count in linux/rwsem-spinlock.h which is
> used when CONFIG_RWSEM_GENERIC_SPINLOCK=y, trying to access it in MIPS
> architecture causes build error due to type mismatch.
>
> error: passing argument 1 of 'atomic_long_read' from incompatible pointer type [-Werror=incompatible-pointer-types]
> note: expected 'const atomic_long_t * {aka const struct <anonymous> *}' but argument is of type '__s32 * {aka int *}'
>
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SKAURA.ne.jp>
> Reported-by: kbuild test robot <lkp@intel.com>
> Fixes: 8ee62b1870be8e63 ("locking/rwsem: Convert sem->count to 'atomic_long_t'")
> Cc: stable <stable@vger.kernel.org> # v4.8+
> Cc: Jason Low <jason.low2@hpe.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> ---
> include/linux/rwsem-spinlock.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
Hmm, how come you don't have to update kernel/locking/rwsem-spinlock.c
as well? I see stuff such as:
sem->count += woken;
in there.
Will
^ permalink raw reply [flat|nested] 11+ messages in thread* Re: [PATCH] locking/lockdep: Dump state of percpu_rwsem upon hung up.
2018-07-10 6:10 ` Tetsuo Handa
2018-07-10 9:20 ` Will Deacon
@ 2018-07-10 9:30 ` Peter Zijlstra
2018-07-10 10:48 ` Tetsuo Handa
2018-07-10 9:41 ` [PATCH] locking/rwsem: Convert the other sem->count to 'atomic_long_t' kbuild test robot
2018-07-10 9:41 ` kbuild test robot
3 siblings, 1 reply; 11+ messages in thread
From: Peter Zijlstra @ 2018-07-10 9:30 UTC (permalink / raw)
To: Tetsuo Handa
Cc: kbuild test robot, kbuild-all, akpm, linux-kernel, Dmitry Vyukov,
Ingo Molnar, Will Deacon
On Tue, Jul 10, 2018 at 03:10:51PM +0900, Tetsuo Handa wrote:
> From 2642b4a1904259384f2018ea8df03ac49509c57a Mon Sep 17 00:00:00 2001
> From: Tetsuo Handa <penguin-kernel@I-love.SKAURA.ne.jp>
> Date: Tue, 10 Jul 2018 15:01:20 +0900
> Subject: [PATCH] locking/rwsem: Convert the other sem->count to 'atomic_long_t'
>
> Since "locking/rwsem: Convert sem->count to 'atomic_long_t'" forgot to
> convert "struct rw_semaphore"->count in linux/rwsem-spinlock.h which is
> used when CONFIG_RWSEM_GENERIC_SPINLOCK=y, trying to access it in MIPS
> architecture causes build error due to type mismatch.
>
> error: passing argument 1 of 'atomic_long_read' from incompatible pointer type [-Werror=incompatible-pointer-types]
> note: expected 'const atomic_long_t * {aka const struct <anonymous> *}' but argument is of type '__s32 * {aka int *}'
>
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SKAURA.ne.jp>
> Reported-by: kbuild test robot <lkp@intel.com>
> Fixes: 8ee62b1870be8e63 ("locking/rwsem: Convert sem->count to 'atomic_long_t'")
> Cc: stable <stable@vger.kernel.org> # v4.8+
> Cc: Jason Low <jason.low2@hpe.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> ---
> include/linux/rwsem-spinlock.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/rwsem-spinlock.h b/include/linux/rwsem-spinlock.h
> index e475683..1164965 100644
> --- a/include/linux/rwsem-spinlock.h
> +++ b/include/linux/rwsem-spinlock.h
> @@ -22,7 +22,7 @@
> * - if wait_list is not empty, then there are processes waiting for the semaphore
> */
> struct rw_semaphore {
> - __s32 count;
> + atomic_long_t count;
Uhhh... how does this even build? rwsem-spinlock.c doesn't use
atomic_long primitives to change count.
And the atomic_long count usage is completely private to rwsem-xadd.c,
nothing outside of that should use that field, ever.
^ permalink raw reply [flat|nested] 11+ messages in thread* Re: [PATCH] locking/lockdep: Dump state of percpu_rwsem upon hung up.
2018-07-10 9:30 ` Peter Zijlstra
@ 2018-07-10 10:48 ` Tetsuo Handa
2018-07-10 11:28 ` Peter Zijlstra
0 siblings, 1 reply; 11+ messages in thread
From: Tetsuo Handa @ 2018-07-10 10:48 UTC (permalink / raw)
To: Peter Zijlstra
Cc: kbuild test robot, kbuild-all, akpm, linux-kernel, Dmitry Vyukov,
Ingo Molnar, Will Deacon
On 2018/07/10 18:30, Peter Zijlstra wrote:
>> diff --git a/include/linux/rwsem-spinlock.h b/include/linux/rwsem-spinlock.h
>> index e475683..1164965 100644
>> --- a/include/linux/rwsem-spinlock.h
>> +++ b/include/linux/rwsem-spinlock.h
>> @@ -22,7 +22,7 @@
>> * - if wait_list is not empty, then there are processes waiting for the semaphore
>> */
>> struct rw_semaphore {
>> - __s32 count;
>> + atomic_long_t count;
>
> Uhhh... how does this even build? rwsem-spinlock.c doesn't use
> atomic_long primitives to change count.
Sorry, I forgot to build test rwsem-spinlock.c side.
>
> And the atomic_long count usage is completely private to rwsem-xadd.c,
> nothing outside of that should use that field, ever.
>
The reason I made above patch is to make
"[PATCH] locking/lockdep: Dump state of percpu_rwsem upon hung up." patch
possible to build on x86_64. Although "nothing outside of that should use
that field", I want to check "struct rw_semaphore"->count for isolating
the problem.
Should I update
"[PATCH] locking/lockdep: Dump state of percpu_rwsem upon hung up." side
to use "#ifndef CONFIG_RWSEM_GENERIC_SPINLOCK" ?
^ permalink raw reply [flat|nested] 11+ messages in thread* Re: [PATCH] locking/lockdep: Dump state of percpu_rwsem upon hung up.
2018-07-10 10:48 ` Tetsuo Handa
@ 2018-07-10 11:28 ` Peter Zijlstra
0 siblings, 0 replies; 11+ messages in thread
From: Peter Zijlstra @ 2018-07-10 11:28 UTC (permalink / raw)
To: Tetsuo Handa
Cc: kbuild test robot, kbuild-all, akpm, linux-kernel, Dmitry Vyukov,
Ingo Molnar, Will Deacon
On Tue, Jul 10, 2018 at 07:48:31PM +0900, Tetsuo Handa wrote:
> Should I update
> "[PATCH] locking/lockdep: Dump state of percpu_rwsem upon hung up." side
> to use "#ifndef CONFIG_RWSEM_GENERIC_SPINLOCK" ?
Since it's a debug patch, who cares if there's a config for which it
doesn't build?
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH] locking/rwsem: Convert the other sem->count to 'atomic_long_t'
2018-07-10 6:10 ` Tetsuo Handa
2018-07-10 9:20 ` Will Deacon
2018-07-10 9:30 ` Peter Zijlstra
@ 2018-07-10 9:41 ` kbuild test robot
2018-07-10 9:41 ` kbuild test robot
3 siblings, 0 replies; 11+ messages in thread
From: kbuild test robot @ 2018-07-10 9:41 UTC (permalink / raw)
To: Tetsuo Handa
Cc: kbuild-all, kbuild test robot, akpm, linux-kernel, Dmitry Vyukov,
Ingo Molnar, Peter Zijlstra, Will Deacon
[-- Attachment #1: Type: text/plain, Size: 2792 bytes --]
Hi Tetsuo,
I love your patch! Perhaps something to improve:
[auto build test WARNING on tip/locking/core]
[also build test WARNING on v4.18-rc4 next-20180709]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
url: https://github.com/0day-ci/linux/commits/Tetsuo-Handa/locking-rwsem-Convert-the-other-sem-count-to-atomic_long_t/20180710-141553
config: m68k-m5475evb_defconfig (attached as .config)
compiler: m68k-linux-gnu-gcc (Debian 7.2.0-11) 7.2.0
reproduce:
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# save the attached .config to linux build tree
GCC_VERSION=7.2.0 make.cross ARCH=m68k
All warnings (new ones prefixed by >>):
In file included from include/linux/notifier.h:15:0,
from include/linux/memory_hotplug.h:7,
from include/linux/mmzone.h:777,
from include/linux/gfp.h:6,
from include/linux/idr.h:16,
from include/linux/kernfs.h:14,
from include/linux/sysfs.h:16,
from include/linux/kobject.h:20,
from include/linux/pci.h:29,
from drivers//pci/search.c:11:
include/linux/rwsem.h:87:2: warning: missing braces around initializer [-Wmissing-braces]
{ __RWSEM_INIT_COUNT(name), \
^
include/linux/rwsem.h:94:29: note: in expansion of macro '__RWSEM_INITIALIZER'
struct rw_semaphore name = __RWSEM_INITIALIZER(name)
^~~~~~~~~~~~~~~~~~~
>> drivers//pci/search.c:17:1: note: in expansion of macro 'DECLARE_RWSEM'
DECLARE_RWSEM(pci_bus_sem);
^~~~~~~~~~~~~
vim +/DECLARE_RWSEM +17 drivers//pci/search.c
^1da177e Linus Torvalds 2005-04-16 @11 #include <linux/pci.h>
5a0e3ad6 Tejun Heo 2010-03-24 12 #include <linux/slab.h>
^1da177e Linus Torvalds 2005-04-16 13 #include <linux/module.h>
^1da177e Linus Torvalds 2005-04-16 14 #include <linux/interrupt.h>
^1da177e Linus Torvalds 2005-04-16 15 #include "pci.h"
^1da177e Linus Torvalds 2005-04-16 16
d71374da Zhang Yanmin 2006-06-02 @17 DECLARE_RWSEM(pci_bus_sem);
ce29ca3e Amos Kong 2012-05-23 18 EXPORT_SYMBOL_GPL(pci_bus_sem);
ce29ca3e Amos Kong 2012-05-23 19
:::::: The code at line 17 was first introduced by commit
:::::: d71374dafbba7ec3f67371d3b7e9f6310a588808 [PATCH] PCI: fix race with pci_walk_bus and pci_destroy_dev
:::::: TO: Zhang Yanmin <yanmin.zhang@intel.com>
:::::: CC: Greg Kroah-Hartman <gregkh@suse.de>
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 6225 bytes --]
^ permalink raw reply [flat|nested] 11+ messages in thread* Re: [PATCH] locking/rwsem: Convert the other sem->count to 'atomic_long_t'
2018-07-10 6:10 ` Tetsuo Handa
` (2 preceding siblings ...)
2018-07-10 9:41 ` [PATCH] locking/rwsem: Convert the other sem->count to 'atomic_long_t' kbuild test robot
@ 2018-07-10 9:41 ` kbuild test robot
3 siblings, 0 replies; 11+ messages in thread
From: kbuild test robot @ 2018-07-10 9:41 UTC (permalink / raw)
To: Tetsuo Handa
Cc: kbuild-all, kbuild test robot, akpm, linux-kernel, Dmitry Vyukov,
Ingo Molnar, Peter Zijlstra, Will Deacon
[-- Attachment #1: Type: text/plain, Size: 3744 bytes --]
Hi Tetsuo,
I love your patch! Perhaps something to improve:
[auto build test WARNING on tip/locking/core]
[also build test WARNING on v4.18-rc4 next-20180709]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
url: https://github.com/0day-ci/linux/commits/Tetsuo-Handa/locking-rwsem-Convert-the-other-sem-count-to-atomic_long_t/20180710-141553
config: parisc-c3000_defconfig (attached as .config)
compiler: hppa-linux-gnu-gcc (Debian 7.2.0-11) 7.2.0
reproduce:
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# save the attached .config to linux build tree
GCC_VERSION=7.2.0 make.cross ARCH=parisc
All warnings (new ones prefixed by >>):
In file included from include/linux/notifier.h:15:0,
from include/linux/memory_hotplug.h:7,
from include/linux/mmzone.h:777,
from include/linux/gfp.h:6,
from include/linux/umh.h:4,
from include/linux/kmod.h:22,
from include/linux/module.h:13,
from drivers/usb/core/hcd-pci.c:7:
include/linux/rwsem.h:87:2: warning: missing braces around initializer [-Wmissing-braces]
{ __RWSEM_INIT_COUNT(name), \
^
include/linux/rwsem.h:94:29: note: in expansion of macro '__RWSEM_INITIALIZER'
struct rw_semaphore name = __RWSEM_INITIALIZER(name)
^~~~~~~~~~~~~~~~~~~
>> drivers/usb/core/hcd-pci.c:31:8: note: in expansion of macro 'DECLARE_RWSEM'
static DECLARE_RWSEM(companions_rwsem);
^~~~~~~~~~~~~
vim +/DECLARE_RWSEM +31 drivers/usb/core/hcd-pci.c
^1da177e4 Linus Torvalds 2005-04-16 @7 #include <linux/module.h>
^1da177e4 Linus Torvalds 2005-04-16 8 #include <linux/pci.h>
21b1861fb David Brownell 2005-11-23 9 #include <linux/usb.h>
27729aadd Eric Lescouet 2010-04-24 10 #include <linux/usb/hcd.h>
21b1861fb David Brownell 2005-11-23 11
^1da177e4 Linus Torvalds 2005-04-16 12 #include <asm/io.h>
^1da177e4 Linus Torvalds 2005-04-16 13 #include <asm/irq.h>
21b1861fb David Brownell 2005-11-23 14
21b1861fb David Brownell 2005-11-23 15 #ifdef CONFIG_PPC_PMAC
21b1861fb David Brownell 2005-11-23 16 #include <asm/machdep.h>
21b1861fb David Brownell 2005-11-23 17 #include <asm/pmac_feature.h>
21b1861fb David Brownell 2005-11-23 18 #include <asm/prom.h>
21b1861fb David Brownell 2005-11-23 19 #endif
5f827ea3c David Brownell 2005-09-22 20
5f827ea3c David Brownell 2005-09-22 21 #include "usb.h"
^1da177e4 Linus Torvalds 2005-04-16 22
^1da177e4 Linus Torvalds 2005-04-16 23
c6053ecff David Brownell 2005-04-18 24 /* PCI-based HCs are common, but plenty of non-PCI HCs are used too */
^1da177e4 Linus Torvalds 2005-04-16 25
05768918b Alan Stern 2013-03-28 26 /*
05768918b Alan Stern 2013-03-28 27 * Coordinate handoffs between EHCI and companion controllers
05768918b Alan Stern 2013-03-28 28 * during EHCI probing and system resume.
6d19c009c Alan Stern 2010-02-12 29 */
6d19c009c Alan Stern 2010-02-12 30
05768918b Alan Stern 2013-03-28 @31 static DECLARE_RWSEM(companions_rwsem);
6d19c009c Alan Stern 2010-02-12 32
:::::: The code at line 31 was first introduced by commit
:::::: 05768918b9a122ce21bd55950df5054ff6c57f28 USB: improve port transitions when EHCI starts up
:::::: TO: Alan Stern <stern@rowland.harvard.edu>
:::::: CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 14543 bytes --]
^ permalink raw reply [flat|nested] 11+ messages in thread
* [PATCH v2] locking/lockdep: Dump state of percpu_rwsem upon hung up.
2018-07-07 6:31 [PATCH] locking/lockdep: Dump state of percpu_rwsem upon hung up Tetsuo Handa
2018-07-07 11:31 ` kbuild test robot
@ 2018-07-10 11:47 ` Tetsuo Handa
1 sibling, 0 replies; 11+ messages in thread
From: Tetsuo Handa @ 2018-07-10 11:47 UTC (permalink / raw)
To: akpm
Cc: linux-kernel, Dmitry Vyukov, Ingo Molnar, Peter Zijlstra, Will Deacon
Added "#ifndef CONFIG_RWSEM_GENERIC_SPINLOCK" check.
From 88f979f8f019f32de94327878ef1f7ccb7500321 Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Date: Tue, 10 Jul 2018 20:43:18 +0900
Subject: [PATCH v2] locking/lockdep: Dump state of percpu_rwsem upon hung up.
This is a temporary patch which should not go to linux.git.
syzbot is hitting hung task problems at __sb_start_write() [1]. While hung
tasks at __sb_start_write() suggest that filesystem was frozen, syzbot is
not doing ioctl(FIFREEZE) requests. Therefore, the root cause of hung tasks
is currently unknown. As a first step for debugging this problem, let's
check what atomic_long_read(&sem->rw_sem.count) says when hung task is
reported. Since it is impossible to reproduce this problem locally, this
patch was made in order to test linux-next.git using syzbot infrastructure.
[1] https://syzkaller.appspot.com/bug?id=287aa8708bc940d0ca1645223c53dd4c2d203be6
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
---
include/linux/sched.h | 1 +
kernel/hung_task.c | 27 +++++++++++++++++++++++++++
kernel/locking/percpu-rwsem.c | 2 ++
3 files changed, 30 insertions(+)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 2974378..df56c65 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1191,6 +1191,7 @@ struct task_struct {
/* Used by LSM modules for access restriction: */
void *security;
#endif
+ struct percpu_rw_semaphore *pcpu_rwsem_read_waiting;
#ifdef CONFIG_GCC_PLUGIN_STACKLEAK
unsigned long lowest_stack;
diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index b9132d1..43975df 100644
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -18,6 +18,7 @@
#include <linux/utsname.h>
#include <linux/sched/signal.h>
#include <linux/sched/debug.h>
+#include <linux/percpu-rwsem.h>
#include <trace/events/sched.h>
@@ -82,6 +83,31 @@ static int __init hung_task_panic_setup(char *str)
.notifier_call = hung_task_panic,
};
+static void dump_percpu_rwsem_state(struct percpu_rw_semaphore *sem)
+{
+#ifndef CONFIG_RWSEM_GENERIC_SPINLOCK
+ unsigned int sum = 0;
+ int cpu;
+
+ if (!sem)
+ return;
+ pr_info("percpu_rw_semaphore(%p)\n", sem);
+ pr_info(" ->rw_sem.count=0x%lx\n",
+ atomic_long_read(&sem->rw_sem.count));
+ pr_info(" ->rss.gp_state=%d\n", sem->rss.gp_state);
+ pr_info(" ->rss.gp_count=%d\n", sem->rss.gp_count);
+ pr_info(" ->rss.cb_state=%d\n", sem->rss.cb_state);
+ pr_info(" ->rss.gp_type=%d\n", sem->rss.gp_type);
+ pr_info(" ->readers_block=%d\n", sem->readers_block);
+ for_each_possible_cpu(cpu)
+ sum += per_cpu(*sem->read_count, cpu);
+ pr_info(" ->read_count=%d\n", sum);
+ pr_info(" ->list_empty(rw_sem.wait_list)=%d\n",
+ list_empty(&sem->rw_sem.wait_list));
+ pr_info(" ->writer.task=%p\n", sem->writer.task);
+#endif
+}
+
static void check_hung_task(struct task_struct *t, unsigned long timeout)
{
unsigned long switch_count = t->nvcsw + t->nivcsw;
@@ -130,6 +156,7 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
pr_err("\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\""
" disables this message.\n");
sched_show_task(t);
+ dump_percpu_rwsem_state(t->pcpu_rwsem_read_waiting);
hung_task_show_lock = true;
}
diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c
index 883cf1b..b3654ab 100644
--- a/kernel/locking/percpu-rwsem.c
+++ b/kernel/locking/percpu-rwsem.c
@@ -82,7 +82,9 @@ int __percpu_down_read(struct percpu_rw_semaphore *sem, int try)
/*
* Avoid lockdep for the down/up_read() we already have them.
*/
+ current->pcpu_rwsem_read_waiting = sem;
__down_read(&sem->rw_sem);
+ current->pcpu_rwsem_read_waiting = NULL;
this_cpu_inc(*sem->read_count);
__up_read(&sem->rw_sem);
--
1.8.3.1
^ permalink raw reply related [flat|nested] 11+ messages in thread
end of thread, other threads:[~2018-07-10 11:48 UTC | newest]
Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-07-07 6:31 [PATCH] locking/lockdep: Dump state of percpu_rwsem upon hung up Tetsuo Handa
2018-07-07 11:31 ` kbuild test robot
2018-07-07 14:09 ` Tetsuo Handa
2018-07-10 6:10 ` Tetsuo Handa
2018-07-10 9:20 ` Will Deacon
2018-07-10 9:30 ` Peter Zijlstra
2018-07-10 10:48 ` Tetsuo Handa
2018-07-10 11:28 ` Peter Zijlstra
2018-07-10 9:41 ` [PATCH] locking/rwsem: Convert the other sem->count to 'atomic_long_t' kbuild test robot
2018-07-10 9:41 ` kbuild test robot
2018-07-10 11:47 ` [PATCH v2] locking/lockdep: Dump state of percpu_rwsem upon hung up Tetsuo Handa
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