From: Anton Vorontsov <anton.vorontsov@linaro.org>
To: Andrew Morton <akpm@linux-foundation.org>,
Oleg Nesterov <oleg@redhat.com>
Cc: 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>,
linux-kernel@vger.kernel.org,
uclinux-dist-devel@blackfin.uclinux.org, linux-mm@kvack.org,
Paul Mundt <lethal@linux-sh.org>,
John Stultz <john.stultz@linaro.org>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
Russell King <linux@arm.linux.org.uk>,
linuxppc-dev@lists.ozlabs.org,
linux-arm-kernel@lists.infradead.org
Subject: [PATCH 03/10] powerpc: Use clear_tasks_mm_cpumask()
Date: Sat, 24 Mar 2012 14:28:31 +0400 [thread overview]
Message-ID: <20120324102831.GC29067@lizard> (raw)
In-Reply-To: <20120324102609.GA28356@lizard>
Current CPU hotplug code has some task->mm handling issues:
1. Working with task->mm w/o getting mm or grabing the task lock is
dangerous as ->mm might disappear (exit_mm() assigns NULL under
task_lock(), so tasklist lock is not enough).
We can't use get_task_mm()/mmput() pair as mmput() might sleep,
so we must take the task lock while handle its mm.
2. Checking for process->mm is not enough because process' main
thread may exit or detach its mm via use_mm(), but other threads
may still have a valid mm.
To fix this we would need to use find_lock_task_mm(), which would
walk up all threads and returns an appropriate task (with task
lock held).
clear_tasks_mm_cpumask() has all the issues fixed, so let's use it.
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
---
arch/powerpc/mm/mmu_context_nohash.c | 11 ++---------
1 file changed, 2 insertions(+), 9 deletions(-)
diff --git a/arch/powerpc/mm/mmu_context_nohash.c b/arch/powerpc/mm/mmu_context_nohash.c
index 5b63bd3..e779642 100644
--- a/arch/powerpc/mm/mmu_context_nohash.c
+++ b/arch/powerpc/mm/mmu_context_nohash.c
@@ -333,9 +333,7 @@ static int __cpuinit mmu_context_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu)
{
unsigned int cpu = (unsigned int)(long)hcpu;
-#ifdef CONFIG_HOTPLUG_CPU
- struct task_struct *p;
-#endif
+
/* We don't touch CPU 0 map, it's allocated at aboot and kept
* around forever
*/
@@ -358,12 +356,7 @@ static int __cpuinit mmu_context_cpu_notify(struct notifier_block *self,
stale_map[cpu] = NULL;
/* We also clear the cpu_vm_mask bits of CPUs going away */
- read_lock(&tasklist_lock);
- for_each_process(p) {
- if (p->mm)
- cpumask_clear_cpu(cpu, mm_cpumask(p->mm));
- }
- read_unlock(&tasklist_lock);
+ clear_tasks_mm_cpumask(cpu);
break;
#endif /* CONFIG_HOTPLUG_CPU */
}
--
1.7.9.2
next prev parent reply other threads:[~2012-03-24 10:29 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-24 10:26 [PATCH v2 0/10] Fixes for common mistakes w/ for_each_process and task->mm Anton Vorontsov
2012-03-24 10:27 ` [PATCH 01/10] cpu: Introduce clear_tasks_mm_cpumask() helper Anton Vorontsov
2012-03-24 12:43 ` Peter Zijlstra
2012-03-24 16:43 ` [PATCH v2.1 " Anton Vorontsov
2012-03-25 17:42 ` Oleg Nesterov
2012-03-26 7:59 ` Peter Zijlstra
2012-03-26 17:04 ` Oleg Nesterov
2012-03-26 17:23 ` Peter Zijlstra
2012-03-28 0:01 ` Benjamin Herrenschmidt
2012-03-24 10:28 ` [PATCH 02/10] arm: Use clear_tasks_mm_cpumask() Anton Vorontsov
2012-03-24 10:28 ` Anton Vorontsov [this message]
2012-03-24 10:28 ` [PATCH 04/10] sh: " Anton Vorontsov
2012-03-24 10:29 ` [PATCH 05/10] blackfin: A couple of task->mm handling fixes Anton Vorontsov
2012-03-24 10:30 ` [PATCH 06/10] blackfin: Fix possible deadlock in decode_address() Anton Vorontsov
2012-03-24 10:30 ` [PATCH 07/10] um: Should hold tasklist_lock while traversing processes Anton Vorontsov
2012-03-24 11:12 ` Richard Weinberger
2012-03-24 12:48 ` Peter Zijlstra
2012-03-24 16:43 ` Anton Vorontsov
2012-03-24 10:30 ` [PATCH 08/10] um: Fix possible race on task->mm Anton Vorontsov
2012-03-24 11:12 ` Richard Weinberger
2012-03-24 10:31 ` [PATCH 09/10] um: Properly check all process' threads for a live mm Anton Vorontsov
2012-03-24 11:12 ` Richard Weinberger
2012-03-24 10:31 ` [PATCH 10/10] oom: Make find_lock_task_mm() sparse-aware Anton Vorontsov
2012-03-24 12:52 ` Peter Zijlstra
2012-03-24 16:21 ` Anton Vorontsov
2012-03-24 16:43 ` Peter Zijlstra
2012-03-28 7:20 ` David Rientjes
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