Re: [Syzkaller & bisect] There is "io_ring_exit_work" related Call Trace in v5.2-rc5 kernel
From: Pengfei Xu
Date: Thu Feb 02 2023 - 03:56:02 EST
Hi Pavel Begunkov,
On 2023-02-01 at 15:52:47 +0000, Pavel Begunkov wrote:
> On 1/28/23 14:49, Pavel Begunkov wrote:
> > On 1/28/23 08:44, Pengfei Xu wrote:
> > > Hi Pavel Begunkov and kernel expert,
> > >
> > > Greeting!
> > >
> > > There is "io_ring_exit_work" related Call Trace in v5.2-rc5 kernel in guest
> > > on Sapphire Rapids server.
> >
> > Thanks for the report, we'll take a look
>
> Not reproducible for me. Apparently, the repro creates a normal ring
> and immediately closes it, then io_ring_exit_work() hangs waiting to
> the task to execute task_work.
Ah, I put the reproduced virtual machine in gitlab.
git clone https://gitlab.com/xupengfe/repro_vm_env.git
cd repro_vm_env
tar -xvf repro_vm_env.tar.gz
cd repro_vm_env; ./start3.sh // it needs qemu-system-x86_64 and I used v7.1.0
//start3.sh will load bzImage_2241ab53cbb5cdb08a6b2d4688feb13971058f65 v6.2-rc5 kernel
In vm and login with root, there is no password for root.
After login vm successfully, ./repro to reproduce this issue.
It could be reproduced in about 6min.
If you already have qemu-system-x86_64, please ignore below info.
If you want to install qemu v7.1.0 version,
git clone https://github.com/qemu/qemu.git
cd qemu
git checkout -f v7.1.0
mkdir build
cd build
yum install -y ninja-build.x86_64
../configure --target-list=x86_64-softmmu --enable-kvm --enable-vnc --enable-gtk --enable-sdl
make
make install
Done.
>
> It reminds me a bug we had before when the task was being stopped
> for debugging blocking task_work. Maybe some signal interaction, or
> vm and/or syz magic specific.
>
Thanks for your info!
I hope it's helpful.
Thanks!
BR.
> > > INFO: task kworker/u4:2:32 blocked for more than 147 seconds.
> > > [ 300.212512] Not tainted 6.2.0-rc5-2241ab53cbb5 #1
> > > [ 300.213087] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> > > [ 300.213921] task:kworker/u4:2 state:D stack:0 pid:32 ppid:2 flags:0x00004000
> > > [ 300.214849] Workqueue: events_unbound io_ring_exit_work
> > > [ 300.215506] Call Trace:
> > > [ 300.215789] <TASK>
> > > [ 300.216051] __schedule+0x385/0xb00
> > > [ 300.216467] ? write_comp_data+0x2f/0x90
> > > [ 300.216949] ? wait_for_completion+0x7b/0x180
> > > [ 300.217445] schedule+0x5b/0xe0
> > > [ 300.217836] schedule_timeout+0x561/0x650
> > > [ 300.218301] ? _raw_spin_unlock_irq+0x2b/0x60
> > > [ 300.218816] ? wait_for_completion+0x7b/0x180
> > > [ 300.219341] ? __this_cpu_preempt_check+0x20/0x30
> > > [ 300.219893] ? lockdep_hardirqs_on+0x8a/0x110
> > > [ 300.220384] ? _raw_spin_unlock_irq+0x2b/0x60
> > > [ 300.220881] ? wait_for_completion+0x9e/0x180
> > > [ 300.221382] ? trace_hardirqs_on+0x3f/0x100
> > > [ 300.221868] ? wait_for_completion+0x7b/0x180
> > > [ 300.222379] wait_for_completion+0xa6/0x180
> > > [ 300.222897] io_ring_exit_work+0x2f7/0x747
> > > [ 300.223383] ? __pfx_io_tctx_exit_cb+0x10/0x10
> > > [ 300.223947] process_one_work+0x3b1/0x960
> > > [ 300.224446] worker_thread+0x52/0x660
> > > [ 300.224884] ? __pfx_worker_thread+0x10/0x10
> > > [ 300.225376] kthread+0x161/0x1a0
> > > [ 300.225782] ? __pfx_kthread+0x10/0x10
> > > [ 300.226225] ret_from_fork+0x29/0x50
> > > [ 300.226688] </TASK>
> > > [ 300.227791]
> > > [ 300.227791] Showing all locks held in the system:
> > > [ 300.228501] 1 lock held by rcu_tasks_kthre/11:
> > > [ 300.229003] #0: ffffffff83d617b0 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x2d/0x3d0
> > > [ 300.230098] 1 lock held by rcu_tasks_rude_/12:
> > > [ 300.230601] #0: ffffffff83d61530 (rcu_tasks_rude.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x2d/0x3d0
> > > [ 300.231733] 1 lock held by rcu_tasks_trace/13:
> > > [ 300.232244] #0: ffffffff83d61270 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x2d/0x3d0
> > > [ 300.233377] 1 lock held by khungtaskd/29:
> > > [ 300.233842] #0: ffffffff83d621c0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x27/0x18c
> > > [ 300.234866] 2 locks held by kworker/u4:2/32:
> > > [ 300.235351] #0: ff11000006045d38 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x2ff/0x960
> > > [ 300.236502] #1: ffa0000000117e60 ((work_completion)(&ctx->exit_work)){+.+.}-{0:0}, at: process_one_work+0x303/0x960
> > > [ 300.237696]
> > > [ 300.237882] =============================================
> > > [ 300.237882]
> > >
> > > Bisected and found the first bad commit is:
> > > eebd2e37e662617a6b8041db75205f0a262ce870
> > > io_uring: don't take task ring-file notes
> > >
> > > But after reverted above commit eebd2e37e on top of v6.2-rc5 kernel and made
> > > the kernel failed. So it's just the suspected commit for above problem.
> > >
> > > Syzkaller reproduced code, bisect info, kconfig and v6.2-rc5 dmesg are in
> > > attached.
> > >
> > > All detailed info is in link:
> > > https://github.com/xupengfe/syzkaller_logs/tree/main/230124_055801_io_ring_exit_work
> > >
> > > I hope it's helpful.
> > >
> > > Thanks!
> > > BR.
> >
>
> --
> Pavel Begunkov