linux-kernel - Re: [syzbot] INFO: task hung in blk_freeze

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Date:   Fri, 02 Sep 2022 18:02:14 -0700
From:   syzbot <syzbot+38e6c55d4969a14c1534@...kaller.appspotmail.com>
To:     hdanton@...a.com, linux-kernel@...r.kernel.org,
        syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] INFO: task hung in blk_freeze_queue (3)

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
INFO: task hung in blkdev_put

INFO: task syz-executor.0:3527 blocked for more than 143 seconds.
      Not tainted 6.0.0-rc3-syzkaller-00299-gd895ec7938c4-dirty #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor.0  state:D stack:    0 pid: 3527 ppid:  3506 flags:0x0000000d
Call trace:
 __switch_to+0x180/0x28c arch/arm64/kernel/process.c:557
 context_switch kernel/sched/core.c:5182 [inline]
 __schedule+0x414/0x570 kernel/sched/core.c:6494
 schedule+0x64/0xa4 kernel/sched/core.c:6570
 schedule_preempt_disabled+0x18/0x2c kernel/sched/core.c:6629
 __mutex_lock_common+0x74c/0xc28 kernel/locking/mutex.c:679
 __mutex_lock kernel/locking/mutex.c:747 [inline]
 mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799
 blkdev_put+0x78/0x270 block/bdev.c:910
 blkdev_close+0x24/0x38 block/fops.c:499
 __fput+0x198/0x3bc fs/file_table.c:320
 ____fput+0x20/0x30 fs/file_table.c:353
 task_work_run+0xc4/0x208 kernel/task_work.c:177
 get_signal+0xac8/0xb30 kernel/signal.c:2634
 do_signal+0x128/0x424 arch/arm64/kernel/signal.c:1071
 do_notify_resume+0xc0/0x1d0 arch/arm64/kernel/signal.c:1124
 prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline]
 exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline]
 el0_svc+0x9c/0x150 arch/arm64/kernel/entry-common.c:625
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:642
 el0t_64_sync+0x18c/0x190

Showing all locks held in the system:
1 lock held by rcu_tasks_kthre/10:
 #0: ffff80000d4a3568 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x3c/0x450 kernel/rcu/tasks.h:507
1 lock held by rcu_tasks_trace/11:
 #0: ffff80000d4a3bb8 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x3c/0x450 kernel/rcu/tasks.h:507
1 lock held by khungtaskd/26:
 #0: ffff80000d4a3440 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x4/0x48 include/linux/rcupdate.h:279
2 locks held by getty/2709:
 #0: ffff0000c6319898 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x28/0x58 drivers/tty/tty_ldisc.c:244
 #1: ffff80000f67e2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x19c/0x88c drivers/tty/n_tty.c:2177
1 lock held by udevd/3505:
 #0: ffff0000c1f45cc8 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_get_by_dev+0xfc/0x2fc block/bdev.c:812
1 lock held by syz-executor.0/3527:
 #0: ffff0000c1f45cc8 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_put+0x78/0x270 block/bdev.c:910
1 lock held by syz-executor.0/3563:
 #0: ffff0000c1f45cc8 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_get_by_dev+0xfc/0x2fc block/bdev.c:812
1 lock held by syz-executor.0/3585:
 #0: ffff0000c1f45cc8 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_get_by_dev+0xfc/0x2fc block/bdev.c:812

=============================================



Tested on:

commit:         d895ec79 Merge tag 'block-6.0-2022-09-02' of git://git..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=101b868b080000
kernel config:  https://syzkaller.appspot.com/x/.config?x=57b9bfeca947ab90
dashboard link: https://syzkaller.appspot.com/bug?extid=38e6c55d4969a14c1534
compiler:       Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
userspace arch: arm64
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1138e4b7080000