public inbox for [email protected]
 help / color / mirror / Atom feed
From: syzbot <[email protected]>
To: [email protected], [email protected],
	[email protected], [email protected],
	[email protected]
Subject: [syzbot] possible deadlock in io_sq_thread
Date: Wed, 08 Sep 2021 17:10:28 -0700	[thread overview]
Message-ID: <[email protected]> (raw)

Hello,

syzbot found the following issue on:

HEAD commit:    a2b28235335f Merge branch 'dmi-for-linus' of git://git.ker..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=175ec47d300000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f5102874b5591af7
dashboard link: https://syzkaller.appspot.com/bug?extid=c9e7f2674197989e8afb
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email protected]

======================================================
WARNING: possible circular locking dependency detected
5.14.0-syzkaller #0 Not tainted
------------------------------------------------------
iou-sqp-17493/17496 is trying to acquire lock:
ffff888084a320a8 (&ctx->uring_lock){+.+.}-{3:3}, at: __io_sq_thread fs/io_uring.c:7291 [inline]
ffff888084a320a8 (&ctx->uring_lock){+.+.}-{3:3}, at: io_sq_thread+0x65a/0x1370 fs/io_uring.c:7368

but task is already holding lock:
ffff888012986870 (&sqd->lock){+.+.}-{3:3}, at: io_sq_thread+0x20f/0x1370 fs/io_uring.c:7356

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&sqd->lock){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:596 [inline]
       __mutex_lock+0x131/0x12f0 kernel/locking/mutex.c:729
       io_register_iowq_max_workers fs/io_uring.c:10551 [inline]
       __io_uring_register fs/io_uring.c:10757 [inline]
       __do_sys_io_uring_register+0x10aa/0x2e70 fs/io_uring.c:10792
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #0 (&ctx->uring_lock){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3051 [inline]
       check_prevs_add kernel/locking/lockdep.c:3174 [inline]
       validate_chain kernel/locking/lockdep.c:3789 [inline]
       __lock_acquire+0x2a07/0x54a0 kernel/locking/lockdep.c:5015
       lock_acquire kernel/locking/lockdep.c:5625 [inline]
       lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5590
       __mutex_lock_common kernel/locking/mutex.c:596 [inline]
       __mutex_lock+0x131/0x12f0 kernel/locking/mutex.c:729
       __io_sq_thread fs/io_uring.c:7291 [inline]
       io_sq_thread+0x65a/0x1370 fs/io_uring.c:7368
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&sqd->lock);
                               lock(&ctx->uring_lock);
                               lock(&sqd->lock);
  lock(&ctx->uring_lock);

 *** DEADLOCK ***

1 lock held by iou-sqp-17493/17496:
 #0: ffff888012986870 (&sqd->lock){+.+.}-{3:3}, at: io_sq_thread+0x20f/0x1370 fs/io_uring.c:7356

stack backtrace:
CPU: 0 PID: 17496 Comm: iou-sqp-17493 Not tainted 5.14.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:105
 check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2131
 check_prev_add kernel/locking/lockdep.c:3051 [inline]
 check_prevs_add kernel/locking/lockdep.c:3174 [inline]
 validate_chain kernel/locking/lockdep.c:3789 [inline]
 __lock_acquire+0x2a07/0x54a0 kernel/locking/lockdep.c:5015
 lock_acquire kernel/locking/lockdep.c:5625 [inline]
 lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5590
 __mutex_lock_common kernel/locking/mutex.c:596 [inline]
 __mutex_lock+0x131/0x12f0 kernel/locking/mutex.c:729
 __io_sq_thread fs/io_uring.c:7291 [inline]
 io_sq_thread+0x65a/0x1370 fs/io_uring.c:7368
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at [email protected].

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

             reply	other threads:[~2021-09-09  0:10 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-09  0:10 syzbot [this message]
2021-09-09  1:02 ` [syzbot] possible deadlock in io_sq_thread Jens Axboe

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox