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From: Qian Cai <cai@lca.pw>
To: Peter Zijlstra <peterz@infradead.org>
Cc: mingo@redhat.com, juri.lelli@redhat.com,
	vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
	rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
	paulmck@kernel.org, tglx@linutronix.de, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] sched/core: fix illegal RCU from offline CPUs
Date: Mon, 20 Jan 2020 15:35:09 -0500	[thread overview]
Message-ID: <F96BF662-BB11-4AFB-BF05-CB1720441A92@lca.pw> (raw)
In-Reply-To: <20200120101652.GM14879@hirez.programming.kicks-ass.net>



> On Jan 20, 2020, at 5:17 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> 
> Bah.. that's horrible. Surely we can find a better place to do this in
> the whole hotplug machinery.
> 
> Perhaps you can have takedown_cpu() do the mmdrop()?

The problem is that no all arch_cpu_idle_dead() will call idle_task_exit(). For example, alpha and parisc are not, so it needs to deal with some kind of ifdef dance in takedown_cpu() to conditionally call mmdrop() which sounds even more horrible?

If you really prefer it anyway, maybe something like touching every arch’s __cpu_die() to also call mmdrop() depends on arches?

BTW, how to obtain the other CPU’s current task mm? Is that cpu_rq(cpu)->curr->active_mm?

  reply	other threads:[~2020-01-20 20:35 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-13 19:03 Qian Cai
2020-01-20 10:16 ` Peter Zijlstra
2020-01-20 20:35   ` Qian Cai [this message]
2020-01-21 10:35     ` Peter Zijlstra
2020-01-24  4:21       ` Qian Cai
2020-01-24  5:02         ` Matthew Wilcox
2020-03-30  2:42       ` Qian Cai
2020-04-01 21:05         ` Qian Cai
2020-04-01 21:40 Qian Cai
2020-04-02 11:24 ` Michael Ellerman
2020-04-02 14:00   ` Qian Cai
2020-04-02 15:54     ` Paul E. McKenney
2020-04-02 16:19       ` Qian Cai
2020-04-02 16:57         ` Paul E. McKenney
2020-04-17 13:26   ` Qian Cai
2020-04-21 13:56     ` Peter Zijlstra

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