On 16/01/2018 5:05 PM, Hannes Reinecke wrote:
> On 01/14/2018 03:42 PM, Coly Li wrote:
>> Kernel thread routine bch_allocator_thread() references macro
>> allocator_wait() to wait for a condition or quit to do_exit()
>> when kthread_should_stop() is true. Here is the code block,
>>
>> 284 while (1) { \
>> 285 set_current_state(TASK_INTERRUPTIBLE); \
>> 286 if (cond) \
>> 287 break; \
>> 288 \
>> 289 mutex_unlock(&(ca)->set->bucket_lock); \
>> 290 if (kthread_should_stop()) \
>> 291 return 0; \
>> 292 \
>> 293 schedule(); \
>> 294 mutex_lock(&(ca)->set->bucket_lock); \
>> 295 } \
>> 296 __set_current_state(TASK_RUNNING); \
>>
>> At line 285, task state is set to TASK_INTERRUPTIBLE, if at line 290
>> kthread_should_stop() is true, the kernel thread will terminate and return
>> to kernel/kthread.s:kthread(), then calls do_exit() with TASK_INTERRUPTIBLE
>> state. This is not a suggested behavior and a warning message will be
>> reported by might_sleep() in do_exit() code path: "WARNING: do not call
>> blocking ops when !TASK_RUNNING; state=1 set at [xxxx]".
>>
>> This patch fixes this problem by setting task state to TASK_RUNNING if
>> kthread_should_stop() is true and before kernel thread returns back to
>> kernel/kthread.s:kthread().
>>
>> Changelog:
>> v2: fix the race issue in v1 patch.
>> v1: initial buggy fix.
>>
>> Signed-off-by: Coly Li <col...@suse.de>
>> Cc: Michael Lyle <ml...@lyle.org>
>> Cc: Hannes Reinecke <h...@suse.de>
>> Cc: Junhui Tang <tang.jun...@zte.com.cn>
>> ---
>> drivers/md/bcache/alloc.c | 4 +++-
>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/md/bcache/alloc.c b/drivers/md/bcache/alloc.c
>> index 6cc6c0f9c3a9..458e1d38577d 100644
>> --- a/drivers/md/bcache/alloc.c
>> +++ b/drivers/md/bcache/alloc.c
>> @@ -287,8 +287,10 @@ do {
>> \
>> break; \
>> \
>> mutex_unlock(&(ca)->set->bucket_lock); \
>> - if (kthread_should_stop()) \
>> + if (kthread_should_stop()) { \
>> + set_current_state(TASK_RUNNING); \
>> return 0; \
>> + } \
>> \
>> schedule(); \
>> mutex_lock(&(ca)->set->bucket_lock); \
>>
> Might be an idea to merge it with the previous patch.
>
> Other than that:
>
> Reviewed-by: Hannes Reinecke <h...@suse.com>
Hi Hannes,
Sure, I will do that in v4 patche set. Thanks for the review.
Coly Li
