Kthread function bch_allocator_thread() references allocator_wait(ca, cond)
and when kthread_should_stop() is true, this kthread exits.
The problem is, if kthread_should_stop() is true, macro allocator_wait()
calls "return 0" with current task state TASK_INTERRUPTIBLE. After function
bch_allocator_thread() returns to do_exit(), there are some blocking
operations are called, then a kenrel warning is popped up by __might_sleep
from kernel/sched/core.c,
"WARNING: do not call blocking ops when !TASK_RUNNING; state=1 set at [xxxx]"
If the task is interrupted and preempted out, since its status is
TASK_INTERRUPTIBLE, it means scheduler won't pick it back to run forever,
and the allocator thread may hang in do_exit().
This patch sets allocator kthread state back to TASK_RUNNING before it
returns to do_exit(), which avoids a potential deadlock.
Signed-off-by: Coly Li <colyli@xxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
drivers/md/bcache/alloc.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/md/bcache/alloc.c b/drivers/md/bcache/alloc.c
index a27d85232ce1..996ebbabd819 100644
--- a/drivers/md/bcache/alloc.c
+++ b/drivers/md/bcache/alloc.c
@@ -286,9 +286,12 @@ do { \
if (cond) \
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); \
--
2.13.6
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