From: "Holger Hoffstätte" <holger@applied-asynchrony.com>
To: Qais Yousef <qais.yousef@arm.com>, Greg KH <gregkh@linuxfoundation.org>
Cc: linux-kernel@vger.kernel.org, linux-tip-commits@vger.kernel.org,
Abhijeet Dharmapurikar <adharmap@quicinc.com>,
Valentin Schneider <valentin.schneider@arm.com>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
"Steven Rostedt (Google)" <rostedt@goodmis.org>,
x86@kernel.org, stable@vger.kernel.org
Subject: Re: [tip: sched/core] sched/tracing: Don't re-read p->state when emitting sched_switch event
Date: Mon, 11 Apr 2022 09:18:19 +0200 [thread overview]
Message-ID: <ae117c69-68e2-93e3-1c0e-f2f4bb9ce03b@applied-asynchrony.com> (raw)
In-Reply-To: <db6ec3a4-3ac9-e96b-d7a5-3e1b4de2adc8@applied-asynchrony.com>
On 2022-04-11 01:22, Holger Hoffstätte wrote:
> On 2022-04-11 00:06, Qais Yousef wrote:
>> On 04/10/22 00:38, Qais Yousef wrote:
>>> On 03/08/22 18:51, Qais Yousef wrote:
>>>> On 03/08/22 19:10, Greg KH wrote:
>>>>> On Tue, Mar 08, 2022 at 06:02:40PM +0000, Qais Yousef wrote:
>>>>>> +CC stable
>>>>>>
>>>>>> On 03/01/22 15:24, tip-bot2 for Valentin Schneider wrote:
>>>>>>> The following commit has been merged into the sched/core branch of tip:
>>>>>>>
>>>>>>> Commit-ID: fa2c3254d7cfff5f7a916ab928a562d1165f17bb
>>>>>>> Gitweb: https://git.kernel.org/tip/fa2c3254d7cfff5f7a916ab928a562d1165f17bb
>>>>>>> Author: Valentin Schneider <valentin.schneider@arm.com>
>>>>>>> AuthorDate: Thu, 20 Jan 2022 16:25:19
>>>>>>> Committer: Peter Zijlstra <peterz@infradead.org>
>>>>>>> CommitterDate: Tue, 01 Mar 2022 16:18:39 +01:00
>>>>>>>
>>>>>>> sched/tracing: Don't re-read p->state when emitting sched_switch event
>>>>>>>
>>>>>>> As of commit
>>>>>>>
>>>>>>> c6e7bd7afaeb ("sched/core: Optimize ttwu() spinning on p->on_cpu")
>>>>>>>
>>>>>>> the following sequence becomes possible:
>>>>>>>
>>>>>>> p->__state = TASK_INTERRUPTIBLE;
>>>>>>> __schedule()
>>>>>>> deactivate_task(p);
>>>>>>> ttwu()
>>>>>>> READ !p->on_rq
>>>>>>> p->__state=TASK_WAKING
>>>>>>> trace_sched_switch()
>>>>>>> __trace_sched_switch_state()
>>>>>>> task_state_index()
>>>>>>> return 0;
>>>>>>>
>>>>>>> TASK_WAKING isn't in TASK_REPORT, so the task appears as TASK_RUNNING in
>>>>>>> the trace event.
>>>>>>>
>>>>>>> Prevent this by pushing the value read from __schedule() down the trace
>>>>>>> event.
>>>>>>>
>>>>>>> Reported-by: Abhijeet Dharmapurikar <adharmap@quicinc.com>
>>>>>>> Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
>>>>>>> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
>>>>>>> Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
>>>>>>> Link: https://lore.kernel.org/r/20220120162520.570782-2-valentin.schneider@arm.com
>>>>>>
>>>>>> Any objection to picking this for stable? I'm interested in this one for some
>>>>>> Android users but prefer if it can be taken by stable rather than backport it
>>>>>> individually.
>>>>>>
>>>>>> I think it makes sense to pick the next one in the series too.
>>>>>
>>>>> What commit does this fix in Linus's tree?
>>>>
>>>> It should be this one: c6e7bd7afaeb ("sched/core: Optimize ttwu() spinning on p->on_cpu")
>>>
>>> Should this be okay to be picked up by stable now? I can see AUTOSEL has picked
>>> it up for v5.15+, but it impacts v5.10 too.
>>
>> commit: fa2c3254d7cfff5f7a916ab928a562d1165f17bb
>> subject: sched/tracing: Don't re-read p->state when emitting sched_switch event
>>
>> This patch has an impact on Android 5.10 users who experience tooling breakage.
>> Is it possible to include in 5.10 LTS please?
>>
>> It was already picked up for 5.15+ by AUTOSEL and only 5.10 is missing.
>>
>
> https://lore.kernel.org/stable/Yk2PQzynOVOzJdPo@kroah.com/
>
> However, since then further investigation (still in progress) has shown that this
> may have been the fault of the tool in question, so if you can verify that tracing
> sched still works for you with this patch in 5.15.x then by all means
> let's merge it.
So it turns out the lockup is indeed the fault of the tool, which contains multiple
kernel-version dependent tracepoint definitions and now fails with this
patch.
Greg, please re-enqueue this patch where necessary (5.10, 5.15+)
-h
next prev parent reply other threads:[~2022-04-11 7:18 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-20 16:25 [PATCH v3 0/2] sched/tracing: sched_switch prev_state reported as TASK_RUNNING when it's not Valentin Schneider
2022-01-20 16:25 ` [PATCH v3 1/2] sched/tracing: Don't re-read p->state when emitting sched_switch event Valentin Schneider
2022-03-01 15:24 ` [tip: sched/core] " tip-bot2 for Valentin Schneider
2022-03-04 16:13 ` Valentin Schneider
2022-03-08 18:02 ` Qais Yousef
2022-03-08 18:10 ` Greg KH
2022-03-08 18:51 ` Qais Yousef
2022-04-09 23:38 ` Qais Yousef
2022-04-10 22:06 ` Qais Yousef
2022-04-10 23:22 ` Holger Hoffstätte
2022-04-11 7:18 ` Holger Hoffstätte [this message]
2022-04-11 7:28 ` Greg KH
2022-04-11 8:05 ` Holger Hoffstätte
2022-04-11 13:23 ` Greg KH
2022-04-11 13:22 ` Greg KH
2022-04-11 21:06 ` Qais Yousef
2022-01-20 16:25 ` [PATCH v3 2/2] sched/tracing: Report TASK_RTLOCK_WAIT tasks as TASK_UNINTERRUPTIBLE Valentin Schneider
2022-03-01 15:24 ` [tip: sched/core] " tip-bot2 for Valentin Schneider
2022-04-09 23:42 ` [PATCH v3 2/2] " Qais Yousef
2022-04-10 6:14 ` Greg KH
2022-04-10 22:13 ` Qais Yousef
2022-04-11 13:20 ` Greg KH
2022-04-11 20:18 ` Qais Yousef
2022-01-21 17:15 ` [PATCH v3 0/2] sched/tracing: sched_switch prev_state reported as TASK_RUNNING when it's not Steven Rostedt
2022-02-27 15:33 ` Peter Zijlstra
2022-04-21 22:12 ` [PATCH] sched/tracing: append prev_state to tp args instead Delyan Kratunov
2022-04-22 10:13 ` Valentin Schneider
2022-04-22 11:09 ` Peter Zijlstra
2022-04-22 15:55 ` Steven Rostedt
2022-04-22 16:54 ` Andrii Nakryiko
2022-04-22 16:37 ` Andrii Nakryiko
2022-04-22 17:22 ` Delyan Kratunov
2022-04-22 18:30 ` Alexei Starovoitov
2022-04-26 12:28 ` Peter Zijlstra
2022-04-26 14:09 ` Qais Yousef
2022-04-26 15:54 ` Andrii Nakryiko
2022-04-27 10:34 ` Qais Yousef
2022-04-27 18:17 ` Andrii Nakryiko
2022-04-27 20:32 ` Alexei Starovoitov
2022-04-28 10:02 ` Qais Yousef
2022-05-09 19:32 ` Andrii Nakryiko
2022-05-10 7:01 ` Peter Zijlstra
2022-05-10 8:29 ` Peter Zijlstra
2022-05-10 14:31 ` Steven Rostedt
2022-05-11 18:28 ` [PATCH v2] " Delyan Kratunov
2022-05-11 19:10 ` Steven Rostedt
2022-05-11 22:45 ` [tip: sched/urgent] sched/tracing: Append " tip-bot2 for Delyan Kratunov
2022-05-11 23:40 ` [PATCH v2] sched/tracing: append " Thomas Gleixner
2022-04-26 15:51 ` [PATCH] " Andrii Nakryiko
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