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Message-ID: <1377784669-28140-6-git-send-email-huawei.libin@huawei.com>
Date: Thu, 29 Aug 2013 21:57:40 +0800
From: Libin <huawei.libin@...wei.com>
To: <akpm@...ux-foundation.org>, <tj@...nel.org>,
<viro@...iv.linux.org.uk>, <eparis@...hat.com>,
<tglx@...utronix.de>, <rusty@...tcorp.com.au>,
<ebiederm@...ssion.com>, <paulmck@...ux.vnet.ibm.com>,
<john.stultz@...aro.org>, <mingo@...hat.com>,
<peterz@...radead.org>, <gregkh@...uxfoundation.org>
CC: <linux-kernel@...r.kernel.org>, <lizefan@...wei.com>,
<jovi.zhangwei@...wei.com>, <guohanjun@...wei.com>,
<zhangdianfang@...wei.com>, <wangyijing@...wei.com>,
<huawei.libin@...wei.com>
Subject: [PATCH 05/14] hrtimer: Fix invalid wakeup in do_nanosleep
If thread is preempted before calling set_current_state(TASK_INTERRUPTIBLE),
and the other thread set the condition followed with wake_up_process. After
that when this thread is re-scheduled, calling set_current_state to set itself
as state TASK_INTERRUPTIBLE, if it is preempted again after that and before
__set_current_state(TASK_RUNNING), it triggers the invalid wakeup problem.
To solve this problem, using preempt_disable() to bound the operaion that
setting the task state and the conditions(set by the wake thread) validation.
Signed-off-by: Libin <huawei.libin@...wei.com>
---
kernel/hrtimer.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 383319b..a7845ba 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1539,14 +1539,18 @@ static int __sched do_nanosleep(struct hrtimer_sleeper *t, enum hrtimer_mode mod
{
hrtimer_init_sleeper(t, current);
+ preempt_disable();
do {
set_current_state(TASK_INTERRUPTIBLE);
hrtimer_start_expires(&t->timer, mode);
if (!hrtimer_active(&t->timer))
t->task = NULL;
- if (likely(t->task))
+ if (likely(t->task)) {
+ preempt_enable();
freezable_schedule();
+ preempt_disable();
+ }
hrtimer_cancel(&t->timer);
mode = HRTIMER_MODE_ABS;
@@ -1554,6 +1558,7 @@ static int __sched do_nanosleep(struct hrtimer_sleeper *t, enum hrtimer_mode mod
} while (t->task && !signal_pending(current));
__set_current_state(TASK_RUNNING);
+ preempt_enable();
return t->task == NULL;
}
--
1.8.2.1
--
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