From ab992dc38f9ae40b3ab996d68449692d464c98cf Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Mon, 18 May 2015 11:31:50 +0200
Subject: [PATCH] watchdog: Fix merge 'conflict'
Two watchdog changes that came through different trees had a non
conflicting conflict, that is, one changed the semantics of a variable
but no actual code conflict happened. So the merge appeared fine, but
the resulting code did not behave as expected.
Commit 195daf665a62 ("watchdog: enable the new user interface of the
watchdog mechanism") changes the semantics of watchdog_user_enabled,
which thereafter is only used by the functions introduced by
b3738d293233 ("watchdog: Add watchdog enable/disable all functions").
There further appears to be a distinct lack of serialization between
setting and using watchdog_enabled, so perhaps we should wrap the
{en,dis}able_all() things in watchdog_proc_mutex.
This patch fixes a s2r failure reported by Michal; which I cannot
readily explain. But this does make the code internally consistent
again.
Reported-and-tested-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
kernel/watchdog.c | 20 +++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 2316f50b07a45..506edcc500c42 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -41,6 +41,8 @@
#define NMI_WATCHDOG_ENABLED (1 << NMI_WATCHDOG_ENABLED_BIT)
#define SOFT_WATCHDOG_ENABLED (1 << SOFT_WATCHDOG_ENABLED_BIT)
+static DEFINE_MUTEX(watchdog_proc_mutex);
+
#ifdef CONFIG_HARDLOCKUP_DETECTOR
static unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED|NMI_WATCHDOG_ENABLED;
#else
@@ -608,26 +610,36 @@ void watchdog_nmi_enable_all(void)
{
int cpu;
- if (!watchdog_user_enabled)
- return;
+ mutex_lock(&watchdog_proc_mutex);
+
+ if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
+ goto unlock;
get_online_cpus();
for_each_online_cpu(cpu)
watchdog_nmi_enable(cpu);
put_online_cpus();
+
+unlock:
+ mutex_lock(&watchdog_proc_mutex);
}
void watchdog_nmi_disable_all(void)
{
int cpu;
+ mutex_lock(&watchdog_proc_mutex);
+
if (!watchdog_running)
- return;
+ goto unlock;
get_online_cpus();
for_each_online_cpu(cpu)
watchdog_nmi_disable(cpu);
put_online_cpus();
+
+unlock:
+ mutex_unlock(&watchdog_proc_mutex);
}
#else
static int watchdog_nmi_enable(unsigned int cpu) { return 0; }
@@ -744,8 +756,6 @@ static int proc_watchdog_update(void)
}
-static DEFINE_MUTEX(watchdog_proc_mutex);
-
/*
* common function for watchdog, nmi_watchdog and soft_watchdog parameter
*
--
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