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Message-ID: <15161e5f-fe26-23e9-1d0a-ebd579d64d9f@gmail.com> Date: Wed, 1 Feb 2023 15:52:47 +0000 From: Pavel Begunkov <asml.silence@...il.com> To: Pengfei Xu <pengfei.xu@...el.com>, linux-kernel@...r.kernel.org Cc: heng.su@...el.com, axboe@...nel.dk Subject: Re: [Syzkaller & bisect] There is "io_ring_exit_work" related Call Trace in v5.2-rc5 kernel 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. 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. >> 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
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