The following commit has been merged in the linux branch: commit 1502f08edc040b6ba4b986454416564088995e79 Author: Tony Luck tony.luck@intel.com Date: Mon Oct 12 09:51:41 2009 -0700

[IA64] SMT friendly version of spin_unlock_wait()

We can be kinder to SMT systems in spin_unlock_wait.

Signed-off-by: Tony Luck tony.luck@intel.com

diff --git a/arch/ia64/include/asm/spinlock.h b/arch/ia64/include/asm/spinlock.h index 4fa5027..239ecdc 100644 --- a/arch/ia64/include/asm/spinlock.h +++ b/arch/ia64/include/asm/spinlock.h @@ -75,6 +75,20 @@ static __always_inline void __ticket_spin_unlock(raw_spinlock_t *lock) ACCESS_ONCE(*p) = (tmp + 2) & ~1; }

+static __always_inline void __ticket_spin_unlock_wait(raw_spinlock_t *lock) +{ + int *p = (int *)&lock->lock, ticket; + + ia64_invala(); + + for (;;) { + asm volatile ("ld4.c.nc %0=[%1]" : "=r"(ticket) : "r"(p) : "memory"); + if (!(((ticket >> TICKET_SHIFT) ^ ticket) & TICKET_MASK)) + return; + cpu_relax(); + } +} + static inline int __ticket_spin_is_locked(raw_spinlock_t *lock) { long tmp = ACCESS_ONCE(lock->lock); @@ -123,8 +137,7 @@ static __always_inline void __raw_spin_lock_flags(raw_spinlock_t *lock,

static inline void __raw_spin_unlock_wait(raw_spinlock_t *lock) { - while (__raw_spin_is_locked(lock)) - cpu_relax(); + __ticket_spin_unlock_wait(lock); }

#define __raw_read_can_lock(rw) (*(volatile int *)(rw) >= 0)