diff options
| author | Steven Rostedt <rostedt@goodmis.org> | 2012-03-02 10:36:57 -0500 |
|---|---|---|
| committer | Clark Williams <williams@redhat.com> | 2012-03-02 11:52:34 -0600 |
| commit | 908b82659598cb1e96abc5f28539a66dfd427643 (patch) | |
| tree | d5f8298b73468444b1d50cedf6e9cf592ae1c0c9 | |
| parent | cc605a8b6bdbbf4b9b54ced270126112cac375dc (diff) | |
cpu: Make hotplug.lock a "sleeping" spinlock on RT
Tasks can block on hotplug.lock in pin_current_cpu(), but their state
might be != RUNNING. So the mutex wakeup will set the state
unconditionally to RUNNING. That might cause spurious unexpected
wakeups. We could provide a state preserving mutex_lock() function,
but this is semantically backwards. So instead we convert the
hotplug.lock() to a spinlock for RT, which has the state preserving
semantics already.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Carsten Emde <C.Emde@osadl.org>
Cc: John Kacur <jkacur@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Clark Williams <clark.williams@gmail.com>
Cc: stable-rt@vger.kernel.org
Link: http://lkml.kernel.org/r/1330702617.25686.265.camel@gandalf.stny.rr.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| -rw-r--r-- | kernel/cpu.c | 31 |
1 files changed, 22 insertions, 9 deletions
diff --git a/kernel/cpu.c b/kernel/cpu.c index fa4083478d75..c25b5ffb63e2 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -46,7 +46,12 @@ static int cpu_hotplug_disabled; static struct { struct task_struct *active_writer; +#ifdef CONFIG_PREEMPT_RT_FULL + /* Makes the lock keep the task's state */ + spinlock_t lock; +#else struct mutex lock; /* Synchronizes accesses to refcount, */ +#endif /* * Also blocks the new readers during * an ongoing cpu hotplug operation. @@ -58,6 +63,14 @@ static struct { .refcount = 0, }; +#ifdef CONFIG_PREEMPT_RT_FULL +# define hotplug_lock() spin_lock(&cpu_hotplug.lock) +# define hotplug_unlock() spin_unlock(&cpu_hotplug.lock) +#else +# define hotplug_lock() mutex_lock(&cpu_hotplug.lock) +# define hotplug_lock() mutex_unlock(&cpu_hotplug.lock) +#endif + struct hotplug_pcp { struct task_struct *unplug; int refcount; @@ -87,8 +100,8 @@ retry: return; } preempt_enable(); - mutex_lock(&cpu_hotplug.lock); - mutex_unlock(&cpu_hotplug.lock); + hotplug_lock(); + hotplug_unlock(); preempt_disable(); goto retry; } @@ -161,9 +174,9 @@ void get_online_cpus(void) might_sleep(); if (cpu_hotplug.active_writer == current) return; - mutex_lock(&cpu_hotplug.lock); + hotplug_lock(); cpu_hotplug.refcount++; - mutex_unlock(&cpu_hotplug.lock); + hotplug_unlock(); } EXPORT_SYMBOL_GPL(get_online_cpus); @@ -172,10 +185,10 @@ void put_online_cpus(void) { if (cpu_hotplug.active_writer == current) return; - mutex_lock(&cpu_hotplug.lock); + hotplug_lock(); if (!--cpu_hotplug.refcount && unlikely(cpu_hotplug.active_writer)) wake_up_process(cpu_hotplug.active_writer); - mutex_unlock(&cpu_hotplug.lock); + hotplug_unlock(); } EXPORT_SYMBOL_GPL(put_online_cpus); @@ -207,11 +220,11 @@ static void cpu_hotplug_begin(void) cpu_hotplug.active_writer = current; for (;;) { - mutex_lock(&cpu_hotplug.lock); + hotplug_lock(); if (likely(!cpu_hotplug.refcount)) break; __set_current_state(TASK_UNINTERRUPTIBLE); - mutex_unlock(&cpu_hotplug.lock); + hotplug_unlock(); schedule(); } } @@ -219,7 +232,7 @@ static void cpu_hotplug_begin(void) static void cpu_hotplug_done(void) { cpu_hotplug.active_writer = NULL; - mutex_unlock(&cpu_hotplug.lock); + hotplug_unlock(); } #else /* #if CONFIG_HOTPLUG_CPU */ |