From: Oleg Nesterov <oleg@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: paulmck@linux.vnet.ibm.com, tj@kernel.org, mingo@redhat.com,
der.herr@hofr.at, dave@stgolabs.net, riel@redhat.com,
viro@ZenIV.linux.org.uk, torvalds@linux-foundation.org,
linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 0/6] stop_machine: kill stop_cpus_mutex and stop_cpus_lock
Date: Tue, 30 Jun 2015 03:08:11 +0200 [thread overview]
Message-ID: <20150630010811.GB22559@redhat.com> (raw)
In-Reply-To: <20150629085127.GF19282@twins.programming.kicks-ass.net>
On 06/29, Peter Zijlstra wrote:
>
> On Mon, Jun 29, 2015 at 06:02:51AM +0200, Oleg Nesterov wrote:
>
> > If we change stop_two_cpus() to use stop_work_alloc_one() it can use
> > cpu_online(),
>
> So the one user of this actually needs cpu_active(); we do not want to
> go move tasks to an inactive cpu.
>
> So if you change this to cpu_online() we need to audit the user is doing
> the stricter test.
Hmm. But the user (migrate_swap_stop) should check cpu_active() anyway?
The cpu_active() checks in stop_two_cpus() can only help to ensure that
multi_cpu_stop() won't hang. CPU_DOWN_PREPARE can deactivate either CPU
right after the check?
Or stop_two_cpus() needs get_online_cpus(). Or I missed something.
Oleg.
next prev parent reply other threads:[~2015-06-30 1:09 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-26 2:14 Oleg Nesterov
2015-06-26 2:15 ` [RFC PATCH 1/6] stop_machine: move cpu_stopper_task and stop_cpus_work into struct cpu_stopper Oleg Nesterov
2015-06-26 2:15 ` [RFC PATCH 2/6] stop_machine: don't do for_each_cpu() twice in queue_stop_cpus_work() Oleg Nesterov
2015-06-26 2:15 ` [RFC PATCH 3/6] stop_machine: introduce stop_work_alloc() and stop_work_free() Oleg Nesterov
2015-06-26 2:15 ` [RFC PATCH 4/6] stop_machine: kill stop_cpus_mutex Oleg Nesterov
2015-06-26 2:15 ` [RFC PATCH 5/6] stop_machine: change stop_two_cpus() just use stop_cpu(), kill lg_double_lock/unlock Oleg Nesterov
2015-06-26 2:15 ` [RFC PATCH 6/6] stop_machine: optimize stop_work_alloc() Oleg Nesterov
2015-06-29 8:56 ` Peter Zijlstra
2015-06-26 2:31 ` [RFC PATCH 0/6] stop_machine: kill stop_cpus_mutex and stop_cpus_lock Oleg Nesterov
2015-06-26 12:23 ` Peter Zijlstra
2015-06-26 20:46 ` Oleg Nesterov
2015-06-29 4:02 ` Oleg Nesterov
2015-06-29 8:51 ` Peter Zijlstra
2015-06-30 1:08 ` Oleg Nesterov [this message]
2015-06-29 8:49 ` Peter Zijlstra
2015-06-30 1:03 ` Oleg Nesterov
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