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authorJeff Moyer <jmoyer@redhat.com>2012-03-05 14:59:12 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2012-03-05 15:49:42 -0800
commit880641bb9da2473e9ecf6c708d993b29928c1b3c (patch)
treef0c73e19cc50010ee04653703d92b243fa0823de /fs/aio.c
parentf986a499ef6f317d906e6f6f281be966e1237a10 (diff)
downloadlinux-stericsson-880641bb9da2473e9ecf6c708d993b29928c1b3c.tar.gz
aio: wake up waiters when freeing unused kiocbs
Bart Van Assche reported a hung fio process when either hot-removing storage or when interrupting the fio process itself. The (pruned) call trace for the latter looks like so: fio D 0000000000000001 0 6849 6848 0x00000004 ffff880092541b88 0000000000000046 ffff880000000000 ffff88012fa11dc0 ffff88012404be70 ffff880092541fd8 ffff880092541fd8 ffff880092541fd8 ffff880128b894d0 ffff88012404be70 ffff880092541b88 000000018106f24d Call Trace: schedule+0x3f/0x60 io_schedule+0x8f/0xd0 wait_for_all_aios+0xc0/0x100 exit_aio+0x55/0xc0 mmput+0x2d/0x110 exit_mm+0x10d/0x130 do_exit+0x671/0x860 do_group_exit+0x44/0xb0 get_signal_to_deliver+0x218/0x5a0 do_signal+0x65/0x700 do_notify_resume+0x65/0x80 int_signal+0x12/0x17 The problem lies with the allocation batching code. It will opportunistically allocate kiocbs, and then trim back the list of iocbs when there is not enough room in the completion ring to hold all of the events. In the case above, what happens is that the pruning back of events ends up freeing up the last active request and the context is marked as dead, so it is thus responsible for waking up waiters. Unfortunately, the code does not check for this condition, so we end up with a hung task. Signed-off-by: Jeff Moyer <jmoyer@redhat.com> Reported-by: Bart Van Assche <bvanassche@acm.org> Tested-by: Bart Van Assche <bvanassche@acm.org> Cc: <stable@kernel.org> [3.2.x only] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/aio.c')
-rw-r--r--fs/aio.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/fs/aio.c b/fs/aio.c
index 969beb0e2231..67e4b9047cc9 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -490,6 +490,8 @@ static void kiocb_batch_free(struct kioctx *ctx, struct kiocb_batch *batch)
kmem_cache_free(kiocb_cachep, req);
ctx->reqs_active--;
}
+ if (unlikely(!ctx->reqs_active && ctx->dead))
+ wake_up_all(&ctx->wait);
spin_unlock_irq(&ctx->ctx_lock);
}