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Merge branch 'core-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

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Pull core/locking changes from Ingo Molnar:
 "Main changes:

   - another mutex optimization, from Davidlohr Bueso

   - improved lglock lockdep tracking, from Michel Lespinasse

   - [ assorted smaller updates, improvements, cleanups. ]"

* 'core-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  generic-ipi/locking: Fix misleading smp_call_function_any() description
  hung_task debugging: Print more info when reporting the problem
  mutex: Avoid label warning when !CONFIG_MUTEX_SPIN_ON_OWNER
  mutex: Do not unnecessarily deal with waiters
  mutex: Fix/document access-once assumption in mutex_can_spin_on_owner()
  lglock: Update lockdep annotations to report recursive local locks
  lockdep: Introduce lock_acquire_exclusive()/shared() helper macros
This commit is contained in:
Linus Torvalds 2013-09-04 08:18:19 -07:00
commit 4689550bb2
5 changed files with 59 additions and 105 deletions
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45
kernel/mutex.c
View file

@ -209,11 +209,13 @@ int mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner)
*/
static inline int mutex_can_spin_on_owner(struct mutex *lock)
{
struct task_struct *owner;
int retval = 1;
rcu_read_lock();
if (lock->owner)
retval = lock->owner->on_cpu;
owner = ACCESS_ONCE(lock->owner);
if (owner)
retval = owner->on_cpu;
rcu_read_unlock();
/*
* if lock->owner is not set, the mutex owner may have just acquired
@ -461,7 +463,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
* performed the optimistic spinning cannot be done.
*/
if (ACCESS_ONCE(ww->ctx))
break;
goto slowpath;
}
/*
@ -472,7 +474,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
owner = ACCESS_ONCE(lock->owner);
if (owner && !mutex_spin_on_owner(lock, owner)) {
mspin_unlock(MLOCK(lock), &node);
break;
goto slowpath;
}
if ((atomic_read(&lock->count) == 1) &&
@ -499,7 +501,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
* the owner complete.
*/
if (!owner && (need_resched() || rt_task(task)))
break;
goto slowpath;
/*
* The cpu_relax() call is a compiler barrier which forces
@ -513,6 +515,10 @@ slowpath:
#endif
spin_lock_mutex(&lock->wait_lock, flags);
/* once more, can we acquire the lock? */
if (MUTEX_SHOW_NO_WAITER(lock) && (atomic_xchg(&lock->count, 0) == 1))
goto skip_wait;
debug_mutex_lock_common(lock, &waiter);
debug_mutex_add_waiter(lock, &waiter, task_thread_info(task));
@ -520,9 +526,6 @@ slowpath:
list_add_tail(&waiter.list, &lock->wait_list);
waiter.task = task;
if (MUTEX_SHOW_NO_WAITER(lock) && (atomic_xchg(&lock->count, -1) == 1))
goto done;
lock_contended(&lock->dep_map, ip);
for (;;) {
@ -536,7 +539,7 @@ slowpath:
* other waiters:
*/
if (MUTEX_SHOW_NO_WAITER(lock) &&
(atomic_xchg(&lock->count, -1) == 1))
(atomic_xchg(&lock->count, -1) == 1))
break;
/*
@ -561,24 +564,25 @@ slowpath:
schedule_preempt_disabled();
spin_lock_mutex(&lock->wait_lock, flags);
}
done:
lock_acquired(&lock->dep_map, ip);
/* got the lock - rejoice! */
mutex_remove_waiter(lock, &waiter, current_thread_info());
/* set it to 0 if there are no waiters left: */
if (likely(list_empty(&lock->wait_list)))
atomic_set(&lock->count, 0);
debug_mutex_free_waiter(&waiter);
skip_wait:
/* got the lock - cleanup and rejoice! */
lock_acquired(&lock->dep_map, ip);
mutex_set_owner(lock);
if (!__builtin_constant_p(ww_ctx == NULL)) {
struct ww_mutex *ww = container_of(lock,
struct ww_mutex,
base);
struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
struct mutex_waiter *cur;
/*
* This branch gets optimized out for the common case,
* and is only important for ww_mutex_lock.
*/
ww_mutex_lock_acquired(ww, ww_ctx);
ww->ctx = ww_ctx;
@ -592,15 +596,8 @@ done:
}
}
/* set it to 0 if there are no waiters left: */
if (likely(list_empty(&lock->wait_list)))
atomic_set(&lock->count, 0);
spin_unlock_mutex(&lock->wait_lock, flags);
debug_mutex_free_waiter(&waiter);
preempt_enable();
return 0;
err: