lkml.org 
[lkml]   [2012]   [Feb]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH 4/8] powerpc/mm: Fix possible race on task->mm
Checking for task->mm 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 let's take the task lock while we care about its mm.

Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
---
arch/powerpc/mm/mmu_context_nohash.c | 3 +++
1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/arch/powerpc/mm/mmu_context_nohash.c b/arch/powerpc/mm/mmu_context_nohash.c
index 5b63bd3..13ec484 100644
--- a/arch/powerpc/mm/mmu_context_nohash.c
+++ b/arch/powerpc/mm/mmu_context_nohash.c
@@ -43,6 +43,7 @@
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/init.h>
+#include <linux/sched.h>
#include <linux/spinlock.h>
#include <linux/bootmem.h>
#include <linux/notifier.h>
@@ -360,8 +361,10 @@ static int __cpuinit mmu_context_cpu_notify(struct notifier_block *self,
/* We also clear the cpu_vm_mask bits of CPUs going away */
read_lock(&tasklist_lock);
for_each_process(p) {
+ task_lock(p);
if (p->mm)
cpumask_clear_cpu(cpu, mm_cpumask(p->mm));
+ task_unlock(p);
}
read_unlock(&tasklist_lock);
break;
--
1.7.7.6


\
 
 \ /
  Last update: 2012-02-07 07:53    [W:0.093 / U:1.232 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site