linux-kernel - [PATCH] hung_task : check the value of "sysctl_hung_task_timeout

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Message-ID: <53182182.3080101@huawei.com>
Date:	Thu, 6 Mar 2014 15:19:30 +0800
From:	Liu hua <sdu.liu@...wei.com>
To:	Ingo Molnar <mingo@...nel.org>
CC:	<oleg@...hat.com>, <paul.gortmaker@...driver.com>,
	Li Zefan <lizefan@...wei.com>, Wang Nan <wangnan0@...wei.com>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH] hung_task : check the value of "sysctl_hung_task_timeout_sec"

As sysctl_hung_task_timeout_sec is unsigned long, when this value is
larger then LONG_MAX, the function schedule_timeout_interruptible in
watchdog will return immediately without sleep :

for example (in x86_64 platform):

linux# echo 0xFFFFFFFFFFFFFFFF > /proc/sys/kernel/hung_task_timeout_secs

[   66.798350] schedule_timeout: wrong timeout value ffffffffffffff06
[   66.800064] schedule_timeout: wrong timeout value ffffffffffffff06
[   66.801774] schedule_timeout: wrong timeout value ffffffffffffff06
[   66.803488] schedule_timeout: wrong timeout value ffffffffffffff06
[   66.805225] schedule_timeout: wrong timeout value ffffffffffffff06

The screen was filled with "schedule_timeout: wrong timeout value
ffffffffffffff06" and the system stalled.

So I do some check and correction in timeout_jiffies, to let the function
schedule_timeout_interruptible allways get the valid parameter.

Signed-off-by: Liu Hua <sdu.liu@...wei.com>
---
 kernel/hung_task.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index 06bb141..ef96650 100644
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -186,7 +186,16 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
 static unsigned long timeout_jiffies(unsigned long timeout)
 {
 	/* timeout of 0 will disable the watchdog */
-	return timeout ? timeout * HZ : MAX_SCHEDULE_TIMEOUT;
+	if ((timeout == 0) || (timeout > MAX_SCHEDULE_TIMEOUT)) {
+		pr_err("%s : wrong timeout value %lx\n",
+					__func__, timeout);
+		pr_err("Timeout value is set to MAX_SCHEDULE_TIMEOUT(%lx) now.\n",
+					MAX_SCHEDULE_TIMEOUT);
+		return MAX_SCHEDULE_TIMEOUT;
+	}
+
+	return (timeout * HZ) < MAX_SCHEDULE_TIMEOUT ?
+			timeout * HZ : MAX_SCHEDULE_TIMEOUT;
 }

 /*
-- 
1.8.5.5.dirty


.




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