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Message-Id: <200702231118.07629.rjw@sisk.pl>
Date: Fri, 23 Feb 2007 11:18:06 +0100
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: LKML <linux-kernel@...r.kernel.org>
Cc: paulmck@...ux.vnet.ibm.com, ego@...ibm.com, akpm@...l.org,
mingo@...e.hu, vatsa@...ibm.com, dipankar@...ibm.com,
venkatesh.pallipadi@...el.com, Pavel Machek <pavel@....cz>,
"Aneesh Kumar" <aneesh.kumar@...il.com>
Subject: [RFC][PATCH 1/7] Freezer: Read PF_BORROWED_MM in a nonracy way
From: Rafael J. Wysocki <rjw@...k.pl>
The reading of PF_BORROWED_MM in is_user_space() without task_lock() is racy.
Fix it.
Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
---
kernel/power/process.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
Index: linux-2.6.20-mm2/kernel/power/process.c
===================================================================
--- linux-2.6.20-mm2.orig/kernel/power/process.c
+++ linux-2.6.20-mm2/kernel/power/process.c
@@ -8,6 +8,7 @@
#undef DEBUG
+#include <linux/sched.h>
#include <linux/smp_lock.h>
#include <linux/interrupt.h>
#include <linux/suspend.h>
@@ -92,7 +93,12 @@ static void cancel_freezing(struct task_
static inline int is_user_space(struct task_struct *p)
{
- return p->mm && !(p->flags & PF_BORROWED_MM);
+ int ret;
+
+ task_lock(p);
+ ret = p->mm && !(p->flags & PF_BORROWED_MM);
+ task_unlock(p);
+ return ret;
}
static unsigned int try_to_freeze_tasks(int freeze_user_space)
-
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