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Merge branch 'locking/urgent' into locking/core, to pick up dependency

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Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Ingo Molnar
2016-06-08 14:35:29 +02:00
parent 331b6d8c7a 2c61002271
commit ae0b5c2f03
2 changed files with 77 additions and 36 deletions
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53
include/asm-generic/qspinlock.h
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@@ -21,38 +21,34 @@
#include <asm-generic/qspinlock_types.h>
/**
* queued_spin_unlock_wait - wait until the _current_ lock holder releases the lock
* @lock : Pointer to queued spinlock structure
*
* There is a very slight possibility of live-lock if the lockers keep coming
* and the waiter is just unfortunate enough to not see any unlock state.
*/
#ifndef queued_spin_unlock_wait
extern void queued_spin_unlock_wait(struct qspinlock *lock);
#endif
/**
* queued_spin_is_locked - is the spinlock locked?
* @lock: Pointer to queued spinlock structure
* Return: 1 if it is locked, 0 otherwise
*/
#ifndef queued_spin_is_locked
static __always_inline int queued_spin_is_locked(struct qspinlock *lock)
{
/*
* queued_spin_lock_slowpath() can ACQUIRE the lock before
* issuing the unordered store that sets _Q_LOCKED_VAL.
* See queued_spin_unlock_wait().
*
* See both smp_cond_acquire() sites for more detail.
*
* This however means that in code like:
*
* spin_lock(A) spin_lock(B)
* spin_unlock_wait(B) spin_is_locked(A)
* do_something() do_something()
*
* Both CPUs can end up running do_something() because the store
* setting _Q_LOCKED_VAL will pass through the loads in
* spin_unlock_wait() and/or spin_is_locked().
*
* Avoid this by issuing a full memory barrier between the spin_lock()
* and the loads in spin_unlock_wait() and spin_is_locked().
*
* Note that regular mutual exclusion doesn't care about this
* delayed store.
* Any !0 state indicates it is locked, even if _Q_LOCKED_VAL
* isn't immediately observable.
*/
smp_mb();
return atomic_read(&lock->val) & _Q_LOCKED_MASK;
return atomic_read(&lock->val);
}
#endif
/**
* queued_spin_value_unlocked - is the spinlock structure unlocked?
@@ -122,21 +118,6 @@ static __always_inline void queued_spin_unlock(struct qspinlock *lock)
}
#endif
/**
* queued_spin_unlock_wait - wait until current lock holder releases the lock
* @lock : Pointer to queued spinlock structure
*
* There is a very slight possibility of live-lock if the lockers keep coming
* and the waiter is just unfortunate enough to not see any unlock state.
*/
static inline void queued_spin_unlock_wait(struct qspinlock *lock)
{
/* See queued_spin_is_locked() */
smp_mb();
while (atomic_read(&lock->val) & _Q_LOCKED_MASK)
cpu_relax();
}
#ifndef virt_spin_lock
static __always_inline bool virt_spin_lock(struct qspinlock *lock)
{