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[IA64] SMT friendly version of spin_unlock_wait()

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We can be kinder to SMT systems in spin_unlock_wait.

Signed-off-by: Tony Luck <tony.luck@intel.com>
This commit is contained in:
Tony Luck 2009-10-12 09:51:41 -07:00
parent 9d40ee200a
commit 1502f08edc
1 changed files with 15 additions and 2 deletions
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17
arch/ia64/include/asm/spinlock.h
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@ -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)