Messages in this thread Patch in this message | | | Date | Sat, 12 Dec 2015 11:23:42 -0500 | From | Chris Mason <> | Subject | [PATCH] lock_page() doesn't lock if __wait_on_bit_lock returns -EINTR |
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We have two reports of frequent crashes in btrfs where asserts in clear_page_dirty_for_io() were triggering on missing page locks.
The crashes were much easier to trigger when processes were catching ctrl-c's, and after much debugging it really looked like lock_page was a noop.
This recent commit looks pretty suspect to me, and I confirmed that we were exiting __wait_on_bit_lock() with -EINTR when it was called with TASK_UNINTERRUPTIBLE
commit 68985633bccb6066bf1803e316fbc6c1f5b796d6 Author: Peter Zijlstra <peterz@infradead.org> Date: Tue Dec 1 14:04:04 2015 +0100
sched/wait: Fix signal handling in bit wait helpers
The patch below is mostly untested, and probably not the right solution. Dave's trinity run doesn't explode immediately anymore, and I wanted to get this out for discussion. A quick look on the list doesn't show anyone else has tracked this down, sorry if it's a dup.
Reported-by: Dave Jones <dsj@fb.com>, Reported-by: Jon Christopherson <jon@jons.org> Signed-off-by: Chris Mason <clm@fb.com>
diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c index f10bd87..12f69df 100644 --- a/kernel/sched/wait.c +++ b/kernel/sched/wait.c @@ -434,6 +434,8 @@ __wait_on_bit_lock(wait_queue_head_t *wq, struct wait_bit_queue *q, ret = action(&q->key); if (!ret) continue; + if (ret == -EINTR && mode == TASK_UNINTERRUPTIBLE) + continue; abort_exclusive_wait(wq, &q->wait, mode, &q->key); return ret; } while (test_and_set_bit(q->key.bit_nr, q->key.flags));
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