diff options
author | Steven Rostedt <rostedt@goodmis.org> | 2012-03-02 10:36:57 -0500 |
---|---|---|
committer | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2016-02-13 00:36:30 +0100 |
commit | e2ec35481943394e95bb11a3964aedbc910786c3 (patch) | |
tree | a9911b8858ada11a7408c3877aebc950cd93cc5f | |
parent | f018d49cd24c9d2fcb4f4f0bdf52fdecea5a1367 (diff) | |
download | rt-linux-e2ec35481943394e95bb11a3964aedbc910786c3.tar.gz |
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>
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 | 34 |
1 files changed, 27 insertions, 7 deletions
diff --git a/kernel/cpu.c b/kernel/cpu.c index d2ff039e5d74ef..503f248f28291e 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -60,10 +60,16 @@ static int cpu_hotplug_disabled; static struct { struct task_struct *active_writer; + /* wait queue to wake up the active_writer */ wait_queue_head_t wq; +#ifdef CONFIG_PREEMPT_RT_FULL + /* Makes the lock keep the task's state */ + spinlock_t lock; +#else /* verifies that no writer will get active while readers are active */ struct mutex lock; +#endif /* * Also blocks the new readers during * an ongoing cpu hotplug operation. @@ -76,12 +82,26 @@ static struct { } cpu_hotplug = { .active_writer = NULL, .wq = __WAIT_QUEUE_HEAD_INITIALIZER(cpu_hotplug.wq), +#ifdef CONFIG_PREEMPT_RT_FULL + .lock = __SPIN_LOCK_UNLOCKED(cpu_hotplug.lock), +#else .lock = __MUTEX_INITIALIZER(cpu_hotplug.lock), +#endif #ifdef CONFIG_DEBUG_LOCK_ALLOC .dep_map = {.name = "cpu_hotplug.lock" }, #endif }; +#ifdef CONFIG_PREEMPT_RT_FULL +# define hotplug_lock() rt_spin_lock(&cpu_hotplug.lock) +# define hotplug_trylock() rt_spin_trylock(&cpu_hotplug.lock) +# define hotplug_unlock() rt_spin_unlock(&cpu_hotplug.lock) +#else +# define hotplug_lock() mutex_lock(&cpu_hotplug.lock) +# define hotplug_trylock() mutex_trylock(&cpu_hotplug.lock) +# define hotplug_unlock() mutex_unlock(&cpu_hotplug.lock) +#endif + /* Lockdep annotations for get/put_online_cpus() and cpu_hotplug_begin/end() */ #define cpuhp_lock_acquire_read() lock_map_acquire_read(&cpu_hotplug.dep_map) #define cpuhp_lock_acquire_tryread() \ @@ -118,8 +138,8 @@ retry: return; } preempt_enable(); - mutex_lock(&cpu_hotplug.lock); - mutex_unlock(&cpu_hotplug.lock); + hotplug_lock(); + hotplug_unlock(); preempt_disable(); goto retry; } @@ -192,9 +212,9 @@ void get_online_cpus(void) if (cpu_hotplug.active_writer == current) return; cpuhp_lock_acquire_read(); - mutex_lock(&cpu_hotplug.lock); + hotplug_lock(); atomic_inc(&cpu_hotplug.refcount); - mutex_unlock(&cpu_hotplug.lock); + hotplug_unlock(); } EXPORT_SYMBOL_GPL(get_online_cpus); @@ -247,11 +267,11 @@ void cpu_hotplug_begin(void) cpuhp_lock_acquire(); for (;;) { - mutex_lock(&cpu_hotplug.lock); + hotplug_lock(); prepare_to_wait(&cpu_hotplug.wq, &wait, TASK_UNINTERRUPTIBLE); if (likely(!atomic_read(&cpu_hotplug.refcount))) break; - mutex_unlock(&cpu_hotplug.lock); + hotplug_unlock(); schedule(); } finish_wait(&cpu_hotplug.wq, &wait); @@ -260,7 +280,7 @@ void cpu_hotplug_begin(void) void cpu_hotplug_done(void) { cpu_hotplug.active_writer = NULL; - mutex_unlock(&cpu_hotplug.lock); + hotplug_unlock(); cpuhp_lock_release(); } |