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watchdog: Fix merge 'conflict'

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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 195daf665a ("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
b3738d2932 ("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>
This commit is contained in:
Peter Zijlstra 2015-05-18 11:31:50 +02:00 committed by Linus Torvalds
parent 7cf7d424c3
commit ab992dc38f
1 changed files with 15 additions and 5 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

20
kernel/watchdog.c
View file

@ -41,6 +41,8 @@
#define NMI_WATCHDOG_ENABLED (1 << NMI_WATCHDOG_ENABLED_BIT) #define NMI_WATCHDOG_ENABLED (1 << NMI_WATCHDOG_ENABLED_BIT)
#define SOFT_WATCHDOG_ENABLED (1 << SOFT_WATCHDOG_ENABLED_BIT) #define SOFT_WATCHDOG_ENABLED (1 << SOFT_WATCHDOG_ENABLED_BIT)
static DEFINE_MUTEX(watchdog_proc_mutex);
#ifdef CONFIG_HARDLOCKUP_DETECTOR #ifdef CONFIG_HARDLOCKUP_DETECTOR
static unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED|NMI_WATCHDOG_ENABLED; static unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED|NMI_WATCHDOG_ENABLED;
#else #else
@ -608,26 +610,36 @@ void watchdog_nmi_enable_all(void)
{ {
int cpu; int cpu;
if (!watchdog_user_enabled) mutex_lock(&watchdog_proc_mutex);
return;
if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
goto unlock;
get_online_cpus(); get_online_cpus();
for_each_online_cpu(cpu) for_each_online_cpu(cpu)
watchdog_nmi_enable(cpu); watchdog_nmi_enable(cpu);
put_online_cpus(); put_online_cpus();
unlock:
mutex_lock(&watchdog_proc_mutex);
} }
void watchdog_nmi_disable_all(void) void watchdog_nmi_disable_all(void)
{ {
int cpu; int cpu;
mutex_lock(&watchdog_proc_mutex);
if (!watchdog_running) if (!watchdog_running)
return; goto unlock;
get_online_cpus(); get_online_cpus();
for_each_online_cpu(cpu) for_each_online_cpu(cpu)
watchdog_nmi_disable(cpu); watchdog_nmi_disable(cpu);
put_online_cpus(); put_online_cpus();
unlock:
mutex_unlock(&watchdog_proc_mutex);
} }
#else #else
static int watchdog_nmi_enable(unsigned int cpu) { return 0; } 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 * common function for watchdog, nmi_watchdog and soft_watchdog parameter
* *