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Message-ID: <4c227812-23ef-4fe8-9bf1-cc4966fd31ac@linux.dev> Date: Thu, 31 Jul 2025 11:25:13 +0800 From: Lance Yang <lance.yang@...ux.dev> To: Sergey Senozhatsky <senozhatsky@...omium.org>, "Masami Hiramatsu (Google)" <mhiramat@...nel.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 2025/7/31 11:15, Lance Yang wrote: > > > On 2025/7/31 10:53, Sergey Senozhatsky 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> >> >> >> Wrote a simple 3 tasks circular lock test (same that I had in real >> life). The output looks good: > > Nice work! The log is now much clearer ;) Forgot to add: This circular lock test is great. It would be very valuable to have it in samples/hung_task ;) Would you be willing to submit it as a patch? Thanks, Lance > >> >> [ 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. >
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