From: Masami Hiramatsu <mhiramat@kernel.org>
To: Uladzislau Rezki <urezki@gmail.com>
Cc: paulmck@kernel.org,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>, RCU <rcu@vger.kernel.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Andrew Morton <akpm@linux-foundation.org>,
Daniel Axtens <dja@axtens.net>,
Frederic Weisbecker <frederic@kernel.org>,
Neeraj Upadhyay <neeraju@codeaurora.org>,
Joel Fernandes <joel@joelfernandes.org>,
Michal Hocko <mhocko@suse.com>,
"Theodore Y . Ts'o" <tytso@mit.edu>,
Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>,
rostedt@goodmis.org
Subject: Re: [PATCH 2/2] rcu-tasks: add RCU-tasks self tests
Date: Thu, 18 Feb 2021 23:29:36 +0900 [thread overview]
Message-ID: <20210218232936.c3158cc304e13151484de3c2@kernel.org> (raw)
In-Reply-To: <20210218083636.GA2030@pc638.lan>
On Thu, 18 Feb 2021 09:36:36 +0100
Uladzislau Rezki <urezki@gmail.com> wrote:
> On Thu, Feb 18, 2021 at 02:03:07PM +0900, Masami Hiramatsu wrote:
> > On Wed, 17 Feb 2021 10:17:38 -0800
> > "Paul E. McKenney" <paulmck@kernel.org> wrote:
> >
> > > > > 1. Spawn ksoftirqd earlier.
> > > > >
> > > > > 2. Suppress attempts to awaken ksoftirqd before it exists,
> > > > > forcing all ksoftirq execution on the back of interrupts.
> > > > >
> > > > > Uladzislau and I each produced patches for #1, and I produced a patch
> > > > > for #2.
> > > > >
> > > > > The only other option I know of is to push the call to init_kprobes()
> > > > > later in the boot sequence, perhaps to its original subsys_initcall(),
> > > > > or maybe only as late as core_initcall(). I added Masami and Steve on
> > > > > CC for their thoughts on this.
> > > > >
> > > > > Is there some other proper fix that I am missing?
> > > >
> > > > Oh, I missed that the synchronize_rcu_tasks() will be involved the kprobes
> > > > in early stage. Does the problem only exist in the synchronize_rcu_tasks()
> > > > instead of synchronize_rcu()? If so I can just stop optimizer in early stage
> > > > because I just want to enable kprobes in early stage, but not optprobes.
> > > >
> > > > Does the following patch help?
> > >
> > > It does look to me like it would! I clearly should have asked you about
> > > this a couple of months ago. ;-)
> > >
> > > The proof of the pudding would be whether the powerpc guys can apply
> > > this to v5.10-rc7 and have their kernel come up without hanging at boot.
> >
> > Who could I ask for testing this patch, Uladzislau?
> > I think the test machine which enough slow or the kernel has much initcall
> > to run optimization thread while booting.
> > In my environment, I could not reproduce that issue because the optimizer
> > was sheduled after some tick passed. At that point, ksoftirqd has already
> > been initialized.
> >
> From my end i did some simulation and had a look at your change. So the
> patch works on my setup. I see that optimization of kprobes is deferred
> and can be initiated only from the subsys_initcall() phase. So the sequence
> should be correct for v5.10-rc7:
>
> 1. ksoftirq is setup early_initcall();
also kprobe framework is initialized in early_initcall() and
kprobes smoketest (register/unregister probes) executed.
> 2. rcu_spawn_tasks_* are setup in the core_initcall();
and kprobe events are setup in core_initcall_sync() (via trace_boot);
> 3. an optimization of kprobes are invoked from subsys_initcall().
At this point, all kprobes which can be optimized will be actually
optimized.
> For real test on power-pc you can ask Daniel Axtens <dja@axtens.net> for help.
OK, I'll CC to Daniel.
Thank you,
--
Masami Hiramatsu <mhiramat@kernel.org>
next prev parent reply other threads:[~2021-02-18 17:24 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-09 20:27 [PATCH 1/2] rcu-tasks: move RCU-tasks initialization out of core_initcall() Uladzislau Rezki (Sony)
2020-12-09 20:27 ` [PATCH 2/2] rcu-tasks: add RCU-tasks self tests Uladzislau Rezki (Sony)
2020-12-16 15:49 ` Uladzislau Rezki
2020-12-16 23:29 ` Paul E. McKenney
2020-12-21 15:38 ` Uladzislau Rezki
2020-12-21 17:18 ` Paul E. McKenney
2020-12-21 18:45 ` Uladzislau Rezki
2020-12-21 19:29 ` Paul E. McKenney
2020-12-21 19:48 ` Uladzislau Rezki
2020-12-21 20:45 ` Paul E. McKenney
2020-12-21 21:28 ` Uladzislau Rezki
2021-02-12 19:20 ` Sebastian Andrzej Siewior
2021-02-12 21:12 ` Uladzislau Rezki
2021-02-12 23:48 ` Paul E. McKenney
2021-02-13 0:37 ` Paul E. McKenney
2021-02-13 0:43 ` Paul E. McKenney
2021-02-13 11:30 ` Uladzislau Rezki
2021-02-13 16:45 ` Paul E. McKenney
2021-02-13 20:00 ` Uladzislau Rezki
2021-02-15 11:28 ` Sebastian Andrzej Siewior
2021-02-16 17:30 ` Paul E. McKenney
2021-02-17 14:47 ` Masami Hiramatsu
2021-02-17 18:17 ` Paul E. McKenney
2021-02-18 5:03 ` Masami Hiramatsu
2021-02-18 8:36 ` Uladzislau Rezki
2021-02-18 14:29 ` Masami Hiramatsu [this message]
2020-12-09 20:37 ` [PATCH 1/2] rcu-tasks: move RCU-tasks initialization out of core_initcall() Uladzislau Rezki
2020-12-10 13:39 ` Daniel Axtens
2020-12-10 17:32 ` Paul E. McKenney
2020-12-10 18:17 ` Uladzislau Rezki
2020-12-10 3:26 ` Paul E. McKenney
2020-12-10 13:04 ` Uladzislau Rezki
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