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Message-Id: <20250731145839.5a27175ebf16e249619fea0d@kernel.org> Date: Thu, 31 Jul 2025 14:58:39 +0900 From: Masami Hiramatsu (Google) <mhiramat@...nel.org> To: Sergey Senozhatsky <senozhatsky@...omium.org> Cc: Andrew Morton <akpm@...ux-foundation.org>, Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>, Boqun Feng <boqun.feng@...il.com>, Waiman Long <longman@...hat.com>, Joel Granados <joel.granados@...nel.org>, Anna Schumaker <anna.schumaker@...cle.com>, Lance Yang <ioworker0@...il.com>, Kent Overstreet <kent.overstreet@...ux.dev>, Yongliang Gao <leonylgao@...cent.com>, Steven Rostedt <rostedt@...dmis.org>, Tomasz Figa <tfiga@...omium.org>, linux-kernel@...r.kernel.org Subject: Re: [PATCH v2] hung_task: Dump blocker task if it is not hung On Thu, 31 Jul 2025 11:53:51 +0900 Sergey Senozhatsky <senozhatsky@...omium.org> wrote: > On (25/07/31 07:11), Masami Hiramatsu (Google) wrote: > > From: Masami Hiramatsu (Google) <mhiramat@...nel.org> > > > > Dump the lock blocker task if it is not hung because if the blocker > > task is also hung, it should be dumped by the detector. This will > > de-duplicate the same stackdumps if the blocker task is also blocked > > by another task (and hung). > > > > Suggested-by: Sergey Senozhatsky <senozhatsky@...omium.org> > > Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org> > > Acked-by: Lance Yang <lance.yang@...ux.dev> > > Tested-by: Sergey Senozhatsky <senozhatsky@...omium.org> > Thank you for testing! > > Wrote a simple 3 tasks circular lock test (same that I had in real > life). The output looks good: OK, it works nicely. We'll better to have a similar test (but with maximum warning message because it can crash the kernel.) Thank you, > > [ 90.985431] [ T140] INFO: task T1:525 blocked for more than 30 seconds. > [ 90.990981] [ T140] Not tainted 6.16.0-next-20250730-00003-g5865c79d6085-dirty #261 > [ 90.996912] [ T140] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > [ 91.001617] [ T140] task:T1 state:D stack:0 pid:525 tgid:525 ppid:2 task_flags:0x208040 flags:0x00004000 > [ 91.007564] [ T140] Call Trace: > [ 91.008767] [ T140] <TASK> > [ 91.009872] [ T140] __schedule+0x137f/0x20c0 > [ 91.011606] [ T140] schedule+0xdc/0x280 > [ 91.013115] [ T140] schedule_preempt_disabled+0x10/0x20 > [ 91.015200] [ T140] __mutex_lock+0x721/0x1590 > [ 91.016817] [ T140] ? __mutex_lock+0x500/0x1590 > [ 91.018074] [ T140] mutex_lock+0x81/0x90 > [ 91.019169] [ T140] t1+0x62/0x70 > [ 91.020061] [ T140] kthread+0x583/0x6e0 > [ 91.021140] [ T140] ? drop_caches_sysctl_handler+0x130/0x130 > [ 91.022729] [ T140] ? kthread_blkcg+0xa0/0xa0 > [ 91.023921] [ T140] ret_from_fork+0xc8/0x160 > [ 91.025091] [ T140] ? kthread_blkcg+0xa0/0xa0 > [ 91.026309] [ T140] ret_from_fork_asm+0x11/0x20 > [ 91.027577] [ T140] </TASK> > [ 91.028326] [ T140] INFO: task T1:525 is blocked on a mutex likely owned by task T2:526. > [ 91.030404] [ T140] INFO: task T2:526 blocked for more than 30 seconds. > [ 91.031978] [ T140] Not tainted 6.16.0-next-20250730-00003-g5865c79d6085-dirty #261 > [ 91.034069] [ T140] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > [ 91.036215] [ T140] task:T2 state:D stack:0 pid:526 tgid:526 ppid:2 task_flags:0x208040 flags:0x00004000 > [ 91.039233] [ T140] Call Trace: > [ 91.040084] [ T140] <TASK> > [ 91.040810] [ T140] __schedule+0x137f/0x20c0 > [ 91.041954] [ T140] schedule+0xdc/0x280 > [ 91.042984] [ T140] schedule_preempt_disabled+0x10/0x20 > [ 91.044329] [ T140] __mutex_lock+0x721/0x1590 > [ 91.045464] [ T140] ? __mutex_lock+0x500/0x1590 > [ 91.046624] [ T140] mutex_lock+0x81/0x90 > [ 91.047632] [ T140] t2+0x69/0x70 > [ 91.048473] [ T140] kthread+0x583/0x6e0 > [ 91.049453] [ T140] ? drop_pagecache_sb+0x200/0x200 > [ 91.050686] [ T140] ? kthread_blkcg+0xa0/0xa0 > [ 91.051808] [ T140] ret_from_fork+0xc8/0x160 > [ 91.052886] [ T140] ? kthread_blkcg+0xa0/0xa0 > [ 91.054036] [ T140] ret_from_fork_asm+0x11/0x20 > [ 91.055205] [ T140] </TASK> > [ 91.056011] [ T140] INFO: task T2:526 is blocked on a mutex likely owned by task T3:527. > [ 91.058014] [ T140] INFO: task T3:527 blocked for more than 30 seconds. > [ 91.059682] [ T140] Not tainted 6.16.0-next-20250730-00003-g5865c79d6085-dirty #261 > [ 91.061708] [ T140] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > [ 91.063825] [ T140] task:T3 state:D stack:0 pid:527 tgid:527 ppid:2 task_flags:0x208040 flags:0x00004000 > [ 91.066668] [ T140] Call Trace: > [ 91.067462] [ T140] <TASK> > [ 91.068121] [ T140] __schedule+0x137f/0x20c0 > [ 91.069244] [ T140] schedule+0xdc/0x280 > [ 91.070264] [ T140] schedule_preempt_disabled+0x10/0x20 > [ 91.071723] [ T140] __mutex_lock+0x721/0x1590 > [ 91.072848] [ T140] ? __mutex_lock+0x500/0x1590 > [ 91.074032] [ T140] mutex_lock+0x81/0x90 > [ 91.075054] [ T140] t3+0x23/0x30 > [ 91.075932] [ T140] kthread+0x583/0x6e0 > [ 91.076953] [ T140] ? t2+0x70/0x70 > [ 91.077865] [ T140] ? kthread_blkcg+0xa0/0xa0 > [ 91.078974] [ T140] ret_from_fork+0xc8/0x160 > [ 91.080109] [ T140] ? kthread_blkcg+0xa0/0xa0 > [ 91.081250] [ T140] ret_from_fork_asm+0x11/0x20 > [ 91.082530] [ T140] </TASK> > [ 91.083248] [ T140] INFO: task T3:527 is blocked on a mutex likely owned by task T1:525. -- Masami Hiramatsu (Google) <mhiramat@...nel.org>
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