diff options
author | Steven Rostedt <rostedt@goodmis.org> | 2012-03-02 15:36:57 (GMT) |
---|---|---|
committer | Scott Wood <scottwood@freescale.com> | 2013-04-04 22:09:34 (GMT) |
commit | bccf7742b7f3b50cbc0087663f5e1bddf88e54af (patch) | |
tree | 29fab77034511d6d10338c4079dee94b155aad07 | |
parent | 5673cd604eeee718e563f6a551a82e7cb48df7d5 (diff) | |
download | linux-fsl-qoriq-bccf7742b7f3b50cbc0087663f5e1bddf88e54af.tar.xz |
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 | 35 |
1 files changed, 26 insertions, 9 deletions
diff --git a/kernel/cpu.c b/kernel/cpu.c index 7b5f4cb..2942f54 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -51,7 +51,12 @@ 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. @@ -59,10 +64,22 @@ static struct { int refcount; } cpu_hotplug = { .active_writer = NULL, +#ifdef CONFIG_PREEMPT_RT_FULL + .lock = __SPIN_LOCK_UNLOCKED(cpu_hotplug.lock), +#else .lock = __MUTEX_INITIALIZER(cpu_hotplug.lock), +#endif .refcount = 0, }; +#ifdef CONFIG_PREEMPT_RT_FULL +# define hotplug_lock() rt_spin_lock(&cpu_hotplug.lock) +# define hotplug_unlock() rt_spin_unlock(&cpu_hotplug.lock) +#else +# define hotplug_lock() mutex_lock(&cpu_hotplug.lock) +# define hotplug_unlock() mutex_unlock(&cpu_hotplug.lock) +#endif + struct hotplug_pcp { struct task_struct *unplug; int refcount; @@ -92,8 +109,8 @@ retry: return; } preempt_enable(); - mutex_lock(&cpu_hotplug.lock); - mutex_unlock(&cpu_hotplug.lock); + hotplug_lock(); + hotplug_unlock(); preempt_disable(); goto retry; } @@ -166,9 +183,9 @@ 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); @@ -177,14 +194,14 @@ void put_online_cpus(void) { if (cpu_hotplug.active_writer == current) return; - mutex_lock(&cpu_hotplug.lock); + hotplug_lock(); if (WARN_ON(!cpu_hotplug.refcount)) cpu_hotplug.refcount++; /* try to fix things up */ 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); @@ -216,11 +233,11 @@ 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(); } } @@ -228,7 +245,7 @@ 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 */ |