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Message-ID: <20120207065054.GF1496@oksana.dev.rtsoft.ru>
Date: Tue, 7 Feb 2012 10:50:54 +0400
From: Anton Vorontsov <anton.vorontsov@...aro.org>
To: Oleg Nesterov <oleg@...hat.com>
Cc: Greg KH <gregkh@...uxfoundation.org>,
KOSAKI Motohiro <kosaki.motohiro@...il.com>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
Paul Mundt <lethal@...ux-sh.org>,
Russell King <linux@....linux.org.uk>,
Mike Frysinger <vapier@...too.org>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Richard Weinberger <richard@....at>,
linux-kernel@...r.kernel.org
Subject: [PATCH 6/8] blackfin: Fix possible race on task->mm
Even when in atomic context, grabbing irqsave variant of tasklist lock
is not enough to protect task->mm from disappearing on SMP machines.
Instead, we have to grab the task lock.
Signed-off-by: Anton Vorontsov <anton.vorontsov@...aro.org>
---
p.s. I don't have blackfin toolchain handy, so I did not build-test
the patch.
arch/blackfin/kernel/trace.c | 21 +++++++++------------
1 files changed, 9 insertions(+), 12 deletions(-)
diff --git a/arch/blackfin/kernel/trace.c b/arch/blackfin/kernel/trace.c
index 050db44..19bc02a 100644
--- a/arch/blackfin/kernel/trace.c
+++ b/arch/blackfin/kernel/trace.c
@@ -10,6 +10,7 @@
#include <linux/hardirq.h>
#include <linux/thread_info.h>
#include <linux/mm.h>
+#include <linux/sched.h>
#include <linux/uaccess.h>
#include <linux/module.h>
#include <linux/kallsyms.h>
@@ -27,7 +28,6 @@ void decode_address(char *buf, unsigned long address)
struct task_struct *p;
struct mm_struct *mm;
unsigned long flags, offset;
- unsigned char in_atomic = (bfin_read_IPEND() & 0x10) || in_atomic();
struct rb_node *n;
#ifdef CONFIG_KALLSYMS
@@ -113,15 +113,13 @@ void decode_address(char *buf, unsigned long address)
*/
write_lock_irqsave(&tasklist_lock, flags);
for_each_process(p) {
- mm = (in_atomic ? p->mm : get_task_mm(p));
+ task_lock(p);
+ mm = p->mm;
if (!mm)
- continue;
+ goto __continue;
- if (!down_read_trylock(&mm->mmap_sem)) {
- if (!in_atomic)
- mmput(mm);
- continue;
- }
+ if (!down_read_trylock(&mm->mmap_sem))
+ goto __continue;
for (n = rb_first(&mm->mm_rb); n; n = rb_next(n)) {
struct vm_area_struct *vma;
@@ -163,8 +161,7 @@ void decode_address(char *buf, unsigned long address)
name, vma->vm_start, vma->vm_end);
up_read(&mm->mmap_sem);
- if (!in_atomic)
- mmput(mm);
+ task_unlock(p);
if (buf[0] == '\0')
sprintf(buf, "[ %s ] dynamic memory", name);
@@ -174,8 +171,8 @@ void decode_address(char *buf, unsigned long address)
}
up_read(&mm->mmap_sem);
- if (!in_atomic)
- mmput(mm);
+__continue:
+ task_unlock(p);
}
/*
--
1.7.7.6
--
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