From: Linus Torvalds <torvalds@linux-foundation.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Vegard Nossum <vegard.nossum@gmail.com>,
Ingo Molnar <mingo@kernel.org>,
Dave Jones <davej@codemonkey.org.uk>, Chris Mason <clm@fb.com>,
Jens Axboe <axboe@fb.com>, Andy Lutomirski <luto@amacapital.net>,
Andy Lutomirski <luto@kernel.org>,
Al Viro <viro@zeniv.linux.org.uk>, Josef Bacik <jbacik@fb.com>,
David Sterba <dsterba@suse.com>,
linux-btrfs <linux-btrfs@vger.kernel.org>,
Linux Kernel <linux-kernel@vger.kernel.org>,
Dave Chinner <david@fromorbit.com>
Subject: Re: bio linked list corruption.
Date: Tue, 6 Dec 2016 08:33:41 -0800 [thread overview]
Message-ID: <CA+55aFzw1_N29mSttZ-TKn7S0-MKbvAfBr4PH+_KBMYr2Uoj+Q@mail.gmail.com> (raw)
In-Reply-To: <20161206081659.GV3092@twins.programming.kicks-ass.net>
On Tue, Dec 6, 2016 at 12:16 AM, Peter Zijlstra <peterz@infradead.org> wrote:
>>
>> Of course, I'm really hoping that this shmem.c use is the _only_ such
>> case. But I doubt it.
>
> $ git grep DECLARE_WAIT_QUEUE_HEAD_ONSTACK | wc -l
> 28
Hmm. Most of them seem to be ok, because they use "wait_event()",
which will always remove itself from the wait-queue. And they do it
from the place that allocates the wait-queue.
IOW, the mm/shmem.c case really was fairly special, because it just
did "prepare_to_wait()", and then did a finish_wait() - and not in the
thread that allocated it on the stack.
So it's really that "some _other_ thread allocated the waitqueue on
the stack, and now we're doing a wait on it" that is bad.
So the normal pattern seems to be:
- allocate wq on the stack
- pass it on to a waker
- wait for it
and that's ok, because as part of "wait for it" we will also be
cleaning things up.
The reason mm/shmem.c was buggy was that it did
- allocate wq on the stack
- pass it on to somebody else to wait for
- wake it up
and *that* is buggy, because it's the waiter, not the waker, that
normally cleans things up.
Is there some good way to find this kind of pattern automatically, I wonder....
Linus
next prev parent reply other threads:[~2016-12-06 16:53 UTC|newest]
Thread overview: 118+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-11 14:45 btrfs bio linked list corruption Dave Jones
2016-10-11 15:11 ` Al Viro
2016-10-11 15:19 ` Dave Jones
2016-10-11 15:20 ` Chris Mason
2016-10-11 15:49 ` Dave Jones
2016-10-11 15:54 ` Chris Mason
2016-10-11 16:25 ` Dave Jones
2016-10-12 13:47 ` Dave Jones
2016-10-12 14:40 ` Dave Jones
2016-10-12 14:42 ` Chris Mason
2016-10-13 18:16 ` Dave Jones
2016-10-13 21:18 ` Chris Mason
2016-10-13 21:56 ` Dave Jones
2016-10-16 0:42 ` Dave Jones
2016-10-18 1:07 ` Chris Mason
2016-10-18 22:42 ` Dave Jones
2016-10-18 23:12 ` Jens Axboe
2016-10-18 23:31 ` Chris Mason
2016-10-18 23:36 ` Jens Axboe
2016-10-18 23:39 ` Linus Torvalds
2016-10-18 23:42 ` Chris Mason
2016-10-19 0:10 ` Linus Torvalds
2016-10-19 0:19 ` Chris Mason
2016-10-19 0:28 ` Linus Torvalds
2016-10-20 22:48 ` Dave Jones
2016-10-19 1:05 ` Andy Lutomirski
2016-10-20 22:50 ` Dave Jones
2016-10-20 23:01 ` Andy Lutomirski
2016-10-20 23:03 ` Dave Jones
2016-10-20 23:23 ` Andy Lutomirski
2016-10-21 20:02 ` Dave Jones
2016-10-21 20:17 ` Chris Mason
2016-10-21 20:23 ` Dave Jones
2016-10-21 20:38 ` Chris Mason
2016-10-21 20:41 ` Josef Bacik
2016-10-21 21:11 ` Dave Jones
2016-10-22 15:20 ` Dave Jones
2016-10-23 21:32 ` Chris Mason
2016-10-24 4:40 ` Dave Jones
2016-10-24 13:42 ` Chris Mason
2016-10-26 0:27 ` Dave Jones
2016-10-26 1:33 ` Linus Torvalds
2016-10-26 1:39 ` Linus Torvalds
2016-10-26 16:30 ` Dave Jones
2016-10-26 16:48 ` Linus Torvalds
2016-10-26 18:18 ` Dave Jones
2016-10-26 18:42 ` Dave Jones
2016-10-26 19:06 ` Linus Torvalds
2016-10-26 20:00 ` Chris Mason
2016-10-26 21:52 ` Chris Mason
2016-10-26 22:21 ` Linus Torvalds
2016-10-26 22:40 ` Dave Jones
2016-10-26 22:51 ` Linus Torvalds
2016-10-26 22:55 ` Jens Axboe
2016-10-26 22:58 ` Linus Torvalds
2016-10-26 23:03 ` Jens Axboe
2016-10-26 23:07 ` Dave Jones
2016-10-26 23:08 ` Linus Torvalds
2016-10-26 23:20 ` Jens Axboe
2016-10-26 23:38 ` Chris Mason
2016-10-26 23:47 ` Dave Jones
2016-10-27 0:00 ` Jens Axboe
2016-10-27 13:33 ` Chris Mason
2016-10-31 18:55 ` Dave Jones
2016-10-31 19:35 ` Linus Torvalds
2016-10-31 19:44 ` Chris Mason
2016-11-06 16:55 ` btrfs btree_ctree_super fault Dave Jones
2016-11-08 14:59 ` Dave Jones
2016-11-08 15:08 ` Chris Mason
2016-11-10 14:35 ` Dave Jones
2016-11-10 15:27 ` Chris Mason
2016-11-23 19:34 ` bio linked list corruption Dave Jones
2016-11-23 19:58 ` Dave Jones
2016-12-01 15:32 ` btrfs_destroy_inode warn (outstanding extents) Dave Jones
2016-12-03 16:48 ` Dave Jones
2016-12-07 16:15 ` Dave Jones
2016-12-09 21:12 ` Steven Rostedt
2016-12-04 23:04 ` bio linked list corruption Vegard Nossum
2016-12-05 11:10 ` Vegard Nossum
2016-12-05 17:09 ` Vegard Nossum
2016-12-05 17:21 ` Dave Jones
2016-12-05 17:55 ` Linus Torvalds
2016-12-05 19:11 ` Vegard Nossum
2016-12-05 20:10 ` Linus Torvalds
2016-12-05 20:35 ` Linus Torvalds
2016-12-05 21:33 ` Vegard Nossum
2016-12-06 8:42 ` Vegard Nossum
2016-12-06 8:16 ` Peter Zijlstra
2016-12-06 8:36 ` Ingo Molnar
2016-12-06 16:33 ` Linus Torvalds [this message]
2016-12-05 20:10 ` Vegard Nossum
2016-12-05 18:11 ` Andy Lutomirski
2016-12-05 18:25 ` Linus Torvalds
2016-12-05 18:26 ` Vegard Nossum
2016-10-26 23:19 ` Chris Mason
2016-10-26 23:21 ` Jens Axboe
2016-10-27 6:33 ` Christoph Hellwig
2016-10-27 16:34 ` Linus Torvalds
2016-10-27 16:36 ` Jens Axboe
2016-10-26 23:01 ` Dave Jones
2016-10-26 23:05 ` Jens Axboe
2016-10-26 22:52 ` Jens Axboe
2016-10-26 22:07 ` Linus Torvalds
2016-10-26 22:54 ` Chris Mason
2016-10-27 5:41 ` Dave Chinner
2016-10-27 17:23 ` Dave Jones
2016-10-24 20:06 ` Andy Lutomirski
2016-10-24 20:46 ` Linus Torvalds
2016-10-24 21:17 ` Linus Torvalds
2016-10-24 21:50 ` Linus Torvalds
2016-10-24 22:02 ` Chris Mason
2016-10-24 22:42 ` Andy Lutomirski
2016-10-25 0:00 ` Linus Torvalds
2016-10-25 1:09 ` Andy Lutomirski
2016-10-19 17:09 ` Philipp Hahn
2016-10-19 17:43 ` Linus Torvalds
2016-10-20 6:52 ` Ingo Molnar
2016-10-20 7:17 ` Thomas Gleixner
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