diff options
| author | Linus Torvalds <torvalds@linux-foundation.org> | 2014-12-09 19:59:22 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-12-09 19:59:22 -0800 |
| commit | 9c37f95936b6c169e89733747504879b06e77c24 (patch) | |
| tree | 9d03d0c8f8b716d7d232975ca6e89f0f33cd1602 /arch | |
| parent | a0e4467726cd26bacb16f13d207ffcfa82ffc07d (diff) | |
| parent | 78bff1c8684fb94f1ae7283688f90188b53fc433 (diff) | |
Merge branch 'core-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking tree changes from Ingo Molnar:
"Two changes: a documentation update and a ticket locks live lock fix"
* 'core-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/ticketlock: Fix spin_unlock_wait() livelock
locking/lglocks: Add documentation of current lglocks implementation
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/include/asm/spinlock.h | 14 |
1 files changed, 13 insertions, 1 deletions
diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h index 9295016485c9..a4efe477ceab 100644 --- a/arch/x86/include/asm/spinlock.h +++ b/arch/x86/include/asm/spinlock.h @@ -183,8 +183,20 @@ static __always_inline void arch_spin_lock_flags(arch_spinlock_t *lock, static inline void arch_spin_unlock_wait(arch_spinlock_t *lock) { - while (arch_spin_is_locked(lock)) + __ticket_t head = ACCESS_ONCE(lock->tickets.head); + + for (;;) { + struct __raw_tickets tmp = ACCESS_ONCE(lock->tickets); + /* + * We need to check "unlocked" in a loop, tmp.head == head + * can be false positive because of overflow. + */ + if (tmp.head == (tmp.tail & ~TICKET_SLOWPATH_FLAG) || + tmp.head != head) + break; + cpu_relax(); + } } /* |