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 <colyli@xxxxxxx>
Cc: Michael Lyle <mlyle@xxxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxx>
Cc: Junhui Tang <tang.junhui@xxxxxxxxxx>
---
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); \
--
2.15.1
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