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

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Pull locking fixes from Ingo Molnar:
 "Spinlock performance regression fix, plus documentation fixes"

* 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  locking/static_keys: Fix up the static keys documentation
  locking/qspinlock/x86: Only emit the test-and-set fallback when building guest support
  locking/qspinlock/x86: Fix performance regression under unaccelerated VMs
  locking/static_keys: Fix a silly typo
This commit is contained in:
Linus Torvalds
2015-09-17 08:45:23 -07:00
parent 1b3dfde386 1975dbc276
commit 9786cff38a
5 changed files with 23 additions and 16 deletions
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19
arch/x86/include/asm/qspinlock.h
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@@ -39,18 +39,27 @@ static inline void queued_spin_unlock(struct qspinlock *lock)
}
#endif
#define virt_queued_spin_lock virt_queued_spin_lock
static inline bool virt_queued_spin_lock(struct qspinlock *lock)
#ifdef CONFIG_PARAVIRT
#define virt_spin_lock virt_spin_lock
static inline bool virt_spin_lock(struct qspinlock *lock)
{
if (!static_cpu_has(X86_FEATURE_HYPERVISOR))
return false;
while (atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL) != 0)
cpu_relax();
/*
* On hypervisors without PARAVIRT_SPINLOCKS support we fall
* back to a Test-and-Set spinlock, because fair locks have
* horrible lock 'holder' preemption issues.
*/
do {
while (atomic_read(&lock->val) != 0)
cpu_relax();
} while (atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL) != 0);
return true;
}
#endif /* CONFIG_PARAVIRT */
#include <asm-generic/qspinlock.h>