linux-kernel - Re: [PATCH] kprobes: Fix to delay the kprobes jump optimization

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Message-ID: <20210219212234.GC2743@paulmck-ThinkPad-P72>
Date:   Fri, 19 Feb 2021 13:22:34 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Uladzislau Rezki <urezki@...il.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>, RCU <rcu@...r.kernel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Daniel Axtens <dja@...ens.net>,
        Frederic Weisbecker <frederic@...nel.org>,
        Neeraj Upadhyay <neeraju@...eaurora.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Michal Hocko <mhocko@...e.com>,
        "Theodore Y . Ts'o" <tytso@....edu>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>
Subject: Re: [PATCH] kprobes: Fix to delay the kprobes jump optimization

On Fri, Feb 19, 2021 at 03:02:31PM -0500, Steven Rostedt wrote:
> On Fri, 19 Feb 2021 10:33:36 -0800
> "Paul E. McKenney" <paulmck@...nel.org> wrote:
> 
> > commit 4f659bf04fc4610523544493d6db92fc8670b086
> > Author: Paul E. McKenney <paulmck@...nel.org>
> > Date:   Fri Feb 12 16:20:40 2021 -0800
> > 
> >     softirq: Don't try waking ksoftirqd before it has been spawned
> >     
> >     If there is heavy softirq activity, the softirq system will attempt
> >     to awaken ksoftirqd and will stop the traditional back-of-interrupt
> >     softirq processing.  This is all well and good, but only if the
> >     ksoftirqd kthreads already exist, which is not the case during early
> >     boot, in which case the system hangs.
> >     
> >     One reproducer is as follows:
> >     
> >     tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 2 --configs "TREE03" --kconfig "CONFIG_DEBUG_LOCK_ALLOC=y CONFIG_PROVE_LOCKING=y" --bootargs "threadirqs=1" --trust-make
> >     
> >     This commit therefore adds a couple of existence checks for ksoftirqd
> >     and forces back-of-interrupt softirq processing when ksoftirqd does not
> >     yet exist.  With this change, the above test passes.
> >     
> >     Reported-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> >     Reported-by: Uladzislau Rezki <urezki@...il.com>
> >     Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
> 
> Hmm, I wonder if this is what patchwork picked up regarding the
> reported-by.
> 
> And I checked, it did not add the "Signed-off-by" from you to Masami's
> patch ;-)
> 
> The dangers of posting patches in threads of other patches :-/

Glad I asked, then!  ;-)

							Thanx, Paul