linux-kernel - Re: [PATCH v4 0/2] rcu: Display registers of self-detected stall as far as possible

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Date:   Fri, 5 Aug 2022 16:09:23 +0800
From:   "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
To:     <paulmck@...nel.org>
CC:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>,
        "Mel Gorman" <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        <linux-kernel@...r.kernel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Neeraj Upadhyay <quic_neeraju@...cinc.com>,
        Josh Triplett <josh@...htriplett.org>,
        "Mathieu Desnoyers" <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>, <rcu@...r.kernel.org>
Subject: Re: [PATCH v4 0/2] rcu: Display registers of self-detected stall as
 far as possible



On 2022/8/5 2:09, Paul E. McKenney wrote:
> On Thu, Aug 04, 2022 at 10:34:18AM +0800, Zhen Lei wrote:
>> v3 --> v4:
>> 1. To avoid undo/redo, merge patch 1-2 in v3 into one.
>>
>> v2 --> v3:
>> 1. Patch 1 Add trigger_single_cpu_backtrace(cpu) in synchronize_rcu_expedited_wait()
>>    Subsequently, we can see that all callers of dump_cpu_task() try
>>    trigger_single_cpu_backtrace() first. Then I do the cleanup in Patch 2.
>> 2. Patch 3, as Paul E. McKenney's suggestion, push the code into dump_cpu_task().
>>
>> For newcomers:
>> Currently, dump_cpu_task() is mainly used by RCU, in order to dump the
>> stack traces of the current task of the specified CPU when a rcu stall
>> is detected.
>>
>> For architectures that do not support NMI interrupts, registers is not
>> printed when rcu stall is self-detected. This patch series improve it.
> 
> Thank you!  I have queued both for further testing and review.  I had
> to rebase them to the -rcu tree's "dev" branch.  There was one trivial
> conflict, but could you please check the resulting commits, both for
> my wordsmithing and to make sure that your changes still work in your
> environment?  (I do not have access to that sort of hardware.)

Your description is much clearer than mine, thanks. I will test it
tomorrow, the international network speed is too slow during the day.

> 
> In the future, could you please send your patches against the -rcu
> tree's "dev" branch?

Okay, no problem. I'll do it next time.

> 
> 							Thanx, Paul
> 
>> v2:
>> https://lkml.org/lkml/2022/7/27/1800
>>
>> Zhen Lei (2):
>>   sched/debug: Try trigger_single_cpu_backtrace(cpu) in dump_cpu_task()
>>   sched/debug: Show the registers of 'current' in dump_cpu_task()
>>
>>  kernel/rcu/tree_stall.h |  8 +++-----
>>  kernel/sched/core.c     | 14 ++++++++++++++
>>  kernel/smp.c            |  3 +--
>>  3 files changed, 18 insertions(+), 7 deletions(-)
>>
>> -- 
>> 2.25.1
>>
> .
> 

-- 
Regards,
  Zhen Lei