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

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Message-ID: <20220804180958.GQ2125313@paulmck-ThinkPad-P17-Gen-1>
Date:   Thu, 4 Aug 2022 11:09:58 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Zhen Lei <thunder.leizhen@...wei.com>
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 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.)

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

							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
>