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From: Anton Vorontsov <anton.vorontsov@linaro.org>
To: linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 1/9] cpu: Introduce clear_tasks_mm_cpumask() helper
Date: Sat, 05 May 2012 01:47:14 +0000	[thread overview]
Message-ID: <20120505014711.GA24566@lizard> (raw)
In-Reply-To: <20120426165911.00cebd31.akpm@linux-foundation.org>

On Thu, Apr 26, 2012 at 04:59:11PM -0700, Andrew Morton wrote:
[...]
> > 	 so its not like new tasks will ever get this cpu set in
> > +	 * their mm mask. -- Peter Zijlstra
> > +	 * Thus, we may use rcu_read_lock() here, instead of grabbing
> > +	 * full-fledged tasklist_lock.
> > +	 */
> > +	rcu_read_lock();
> > +	for_each_process(p) {
> > +		struct task_struct *t;
> > +
> > +		t = find_lock_task_mm(p);
> > +		if (!t)
> > +			continue;
> > +		cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
> > +		task_unlock(t);
> > +	}
> > +	rcu_read_unlock();
> > +}
> 
> It is good that this code exists under CONFIG_HOTPLUG_CPU.  Did you
> check that everything works correctly with CONFIG_HOTPLUG_CPU=n?

Yeah, only the code under CONFIG_HOTPLUG_CPU calls the function, so
it should be all fine.

Thanks!

-- 
Anton Vorontsov
Email: cbouatmailru@gmail.com

WARNING: multiple messages have this Message-ID (diff)
From: Anton Vorontsov <anton.vorontsov@linaro.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>,
	Russell King <linux@arm.linux.org.uk>,
	Mike Frysinger <vapier@gentoo.org>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Richard Weinberger <richard@nod.at>,
	Paul Mundt <lethal@linux-sh.org>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
	John Stultz <john.stultz@linaro.org>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org,
	uclinux-dist-devel@blackfin.uclinux.org,
	linuxppc-dev@lists.ozlabs.org, linux-sh@vger.kernel.org,
	user-mode-linux-devel@lists.sourceforge.net,
	linaro-kernel@lists.linaro.org, patches@linaro.org,
	linux-mm@kvack.org
Subject: Re: [PATCH 1/9] cpu: Introduce clear_tasks_mm_cpumask() helper
Date: Fri, 4 May 2012 18:47:14 -0700	[thread overview]
Message-ID: <20120505014711.GA24566@lizard> (raw)
In-Reply-To: <20120426165911.00cebd31.akpm@linux-foundation.org>

On Thu, Apr 26, 2012 at 04:59:11PM -0700, Andrew Morton wrote:
[...]
> > 	 so its not like new tasks will ever get this cpu set in
> > +	 * their mm mask. -- Peter Zijlstra
> > +	 * Thus, we may use rcu_read_lock() here, instead of grabbing
> > +	 * full-fledged tasklist_lock.
> > +	 */
> > +	rcu_read_lock();
> > +	for_each_process(p) {
> > +		struct task_struct *t;
> > +
> > +		t = find_lock_task_mm(p);
> > +		if (!t)
> > +			continue;
> > +		cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
> > +		task_unlock(t);
> > +	}
> > +	rcu_read_unlock();
> > +}
> 
> It is good that this code exists under CONFIG_HOTPLUG_CPU.  Did you
> check that everything works correctly with CONFIG_HOTPLUG_CPU=n?

Yeah, only the code under CONFIG_HOTPLUG_CPU calls the function, so
it should be all fine.

Thanks!

-- 
Anton Vorontsov
Email: cbouatmailru@gmail.com

WARNING: multiple messages have this Message-ID (diff)
From: Anton Vorontsov <anton.vorontsov@linaro.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linaro-kernel@lists.linaro.org,
	Mike Frysinger <vapier@gentoo.org>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	user-mode-linux-devel@lists.sourceforge.net,
	linux-sh@vger.kernel.org, Richard Weinberger <richard@nod.at>,
	linuxppc-dev@lists.ozlabs.org, Oleg Nesterov <oleg@redhat.com>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	Paul Mundt <lethal@linux-sh.org>,
	John Stultz <john.stultz@linaro.org>,
	patches@linaro.org,
	KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
	Russell King <linux@arm.linux.org.uk>,
	uclinux-dist-devel@blackfin.uclinux.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 1/9] cpu: Introduce clear_tasks_mm_cpumask() helper
Date: Fri, 4 May 2012 18:47:14 -0700	[thread overview]
Message-ID: <20120505014711.GA24566@lizard> (raw)
In-Reply-To: <20120426165911.00cebd31.akpm@linux-foundation.org>

On Thu, Apr 26, 2012 at 04:59:11PM -0700, Andrew Morton wrote:
[...]
> > 	 so its not like new tasks will ever get this cpu set in
> > +	 * their mm mask. -- Peter Zijlstra
> > +	 * Thus, we may use rcu_read_lock() here, instead of grabbing
> > +	 * full-fledged tasklist_lock.
> > +	 */
> > +	rcu_read_lock();
> > +	for_each_process(p) {
> > +		struct task_struct *t;
> > +
> > +		t = find_lock_task_mm(p);
> > +		if (!t)
> > +			continue;
> > +		cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
> > +		task_unlock(t);
> > +	}
> > +	rcu_read_unlock();
> > +}
> 
> It is good that this code exists under CONFIG_HOTPLUG_CPU.  Did you
> check that everything works correctly with CONFIG_HOTPLUG_CPU=n?

Yeah, only the code under CONFIG_HOTPLUG_CPU calls the function, so
it should be all fine.

Thanks!

-- 
Anton Vorontsov
Email: cbouatmailru@gmail.com

WARNING: multiple messages have this Message-ID (diff)
From: anton.vorontsov@linaro.org (Anton Vorontsov)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 1/9] cpu: Introduce clear_tasks_mm_cpumask() helper
Date: Fri, 4 May 2012 18:47:14 -0700	[thread overview]
Message-ID: <20120505014711.GA24566@lizard> (raw)
In-Reply-To: <20120426165911.00cebd31.akpm@linux-foundation.org>

On Thu, Apr 26, 2012 at 04:59:11PM -0700, Andrew Morton wrote:
[...]
> > 	 so its not like new tasks will ever get this cpu set in
> > +	 * their mm mask. -- Peter Zijlstra
> > +	 * Thus, we may use rcu_read_lock() here, instead of grabbing
> > +	 * full-fledged tasklist_lock.
> > +	 */
> > +	rcu_read_lock();
> > +	for_each_process(p) {
> > +		struct task_struct *t;
> > +
> > +		t = find_lock_task_mm(p);
> > +		if (!t)
> > +			continue;
> > +		cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
> > +		task_unlock(t);
> > +	}
> > +	rcu_read_unlock();
> > +}
> 
> It is good that this code exists under CONFIG_HOTPLUG_CPU.  Did you
> check that everything works correctly with CONFIG_HOTPLUG_CPU=n?

Yeah, only the code under CONFIG_HOTPLUG_CPU calls the function, so
it should be all fine.

Thanks!

-- 
Anton Vorontsov
Email: cbouatmailru at gmail.com

WARNING: multiple messages have this Message-ID (diff)
From: Anton Vorontsov <anton.vorontsov@linaro.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>,
	Russell King <linux@arm.linux.org.uk>,
	Mike Frysinger <vapier@gentoo.org>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Richard Weinberger <richard@nod.at>,
	Paul Mundt <lethal@linux-sh.org>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
	John Stultz <john.stultz@linaro.org>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org,
	uclinux-dist-devel@blackfin.uclinux.org,
	linuxppc-dev@lists.ozlabs.org, linux-sh@vger.kernel.org,
	user-mode-linux-devel@lists.sourceforge.net,
	linaro-kernel@lists.linaro.org, patches@linaro.org,
	linux-mm@kvack.org
Subject: Re: [PATCH 1/9] cpu: Introduce clear_tasks_mm_cpumask() helper
Date: Fri, 4 May 2012 18:47:14 -0700	[thread overview]
Message-ID: <20120505014711.GA24566@lizard> (raw)
In-Reply-To: <20120426165911.00cebd31.akpm@linux-foundation.org>

On Thu, Apr 26, 2012 at 04:59:11PM -0700, Andrew Morton wrote:
[...]
> > 	 so its not like new tasks will ever get this cpu set in
> > +	 * their mm mask. -- Peter Zijlstra
> > +	 * Thus, we may use rcu_read_lock() here, instead of grabbing
> > +	 * full-fledged tasklist_lock.
> > +	 */
> > +	rcu_read_lock();
> > +	for_each_process(p) {
> > +		struct task_struct *t;
> > +
> > +		t = find_lock_task_mm(p);
> > +		if (!t)
> > +			continue;
> > +		cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
> > +		task_unlock(t);
> > +	}
> > +	rcu_read_unlock();
> > +}
> 
> It is good that this code exists under CONFIG_HOTPLUG_CPU.  Did you
> check that everything works correctly with CONFIG_HOTPLUG_CPU=n?

Yeah, only the code under CONFIG_HOTPLUG_CPU calls the function, so
it should be all fine.

Thanks!

-- 
Anton Vorontsov
Email: cbouatmailru@gmail.com

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  parent reply	other threads:[~2012-05-05  1:47 UTC|newest]

Thread overview: 85+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-04-23  7:06 [PATCH v3 0/9] Fixes for common mistakes w/ for_each_process and task->mm Anton Vorontsov
2012-04-23  7:06 ` Anton Vorontsov
2012-04-23  7:06 ` Anton Vorontsov
2012-04-23  7:06 ` Anton Vorontsov
2012-04-23  7:06 ` Anton Vorontsov
2012-04-23  7:07 ` [PATCH 1/9] cpu: Introduce clear_tasks_mm_cpumask() helper Anton Vorontsov
2012-04-23  7:07   ` Anton Vorontsov
2012-04-23  7:07   ` Anton Vorontsov
2012-04-23  7:07   ` Anton Vorontsov
2012-04-23  7:07   ` Anton Vorontsov
2012-04-26 23:59   ` Andrew Morton
2012-04-26 23:59     ` Andrew Morton
2012-04-26 23:59     ` Andrew Morton
2012-04-26 23:59     ` Andrew Morton
2012-04-26 23:59     ` Andrew Morton
2012-04-26 23:59     ` Andrew Morton
2012-05-01 10:45     ` Peter Zijlstra
2012-05-01 10:45       ` Peter Zijlstra
2012-05-01 10:45       ` Peter Zijlstra
2012-05-01 10:45       ` Peter Zijlstra
2012-05-01 10:45       ` Peter Zijlstra
2012-05-05  1:47       ` [PATCH] cpu: Document clear_tasks_mm_cpumask() Anton Vorontsov
2012-05-05  1:47         ` Anton Vorontsov
2012-05-05  1:47         ` Anton Vorontsov
2012-05-05  1:47         ` Anton Vorontsov
2012-05-05  1:47         ` Anton Vorontsov
2012-05-05  1:47     ` Anton Vorontsov [this message]
2012-05-05  1:47       ` [PATCH 1/9] cpu: Introduce clear_tasks_mm_cpumask() helper Anton Vorontsov
2012-05-05  1:47       ` Anton Vorontsov
2012-05-05  1:47       ` Anton Vorontsov
2012-05-05  1:47       ` Anton Vorontsov
2012-04-23  7:08 ` [PATCH 2/9] arm: Use clear_tasks_mm_cpumask() Anton Vorontsov
2012-04-23  7:08   ` Anton Vorontsov
2012-04-23  7:08   ` Anton Vorontsov
2012-04-23  7:08   ` Anton Vorontsov
2012-04-23  7:08   ` Anton Vorontsov
2012-04-23  7:08 ` [PATCH 3/9] powerpc: " Anton Vorontsov
2012-04-23  7:08   ` Anton Vorontsov
2012-04-23  7:08   ` Anton Vorontsov
2012-04-23  7:08   ` Anton Vorontsov
2012-04-23  7:08   ` Anton Vorontsov
2012-04-23  7:08 ` [PATCH 4/9] sh: " Anton Vorontsov
2012-04-23  7:08   ` Anton Vorontsov
2012-04-23  7:08   ` Anton Vorontsov
2012-04-23  7:08   ` Anton Vorontsov
2012-04-23  7:08   ` Anton Vorontsov
2012-04-23  7:09 ` [PATCH 5/9] blackfin: A couple of task->mm handling fixes Anton Vorontsov
2012-04-23  7:09   ` Anton Vorontsov
2012-04-23  7:09   ` Anton Vorontsov
2012-04-23  7:09   ` Anton Vorontsov
2012-04-23  7:09   ` Anton Vorontsov
2012-06-01  4:36   ` Mike Frysinger
2012-06-01  4:36     ` Mike Frysinger
2012-06-01  4:36     ` Mike Frysinger
2012-06-01  4:36     ` Mike Frysinger
2012-04-23  7:09 ` [PATCH 6/9] blackfin: Fix possible deadlock in decode_address() Anton Vorontsov
2012-04-23  7:09   ` Anton Vorontsov
2012-04-23  7:09   ` Anton Vorontsov
2012-04-23  7:09   ` Anton Vorontsov
2012-04-23  7:09   ` Anton Vorontsov
2012-04-23  7:09 ` [PATCH 7/9] um: Should hold tasklist_lock while traversing processes Anton Vorontsov
2012-04-23  7:09   ` Anton Vorontsov
2012-04-23  7:09   ` Anton Vorontsov
2012-04-23  7:09   ` Anton Vorontsov
2012-04-23  7:09   ` Anton Vorontsov
2012-04-23 14:57   ` Richard Weinberger
2012-04-23 14:57     ` Richard Weinberger
2012-04-23 14:57     ` Richard Weinberger
2012-04-23 14:57     ` Richard Weinberger
2012-04-23 14:57     ` Richard Weinberger
2012-04-23 15:40     ` Anton Vorontsov
2012-04-23 15:40       ` Anton Vorontsov
2012-04-23 15:40       ` Anton Vorontsov
2012-04-23 15:40       ` Anton Vorontsov
2012-04-23 15:40       ` Anton Vorontsov
2012-04-23  7:09 ` [PATCH 8/9] um: Fix possible race on task->mm Anton Vorontsov
2012-04-23  7:09   ` Anton Vorontsov
2012-04-23  7:09   ` Anton Vorontsov
2012-04-23  7:09   ` Anton Vorontsov
2012-04-23  7:09   ` Anton Vorontsov
2012-04-23  7:09 ` [PATCH 9/9] um: Properly check all process' threads for a live mm Anton Vorontsov
2012-04-23  7:09   ` Anton Vorontsov
2012-04-23  7:09   ` Anton Vorontsov
2012-04-23  7:09   ` Anton Vorontsov
2012-04-23  7:09   ` Anton Vorontsov

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