It is better to use smp_cond_load_relaxed instead
of busy waiting for bit_spinlock.
Signed-off-by: Gao Xiang <hsiang...@aol.com>
---
include/linux/bit_spinlock.h | 21 ++++++++-------------
1 file changed, 8 insertions(+), 13 deletions(-)
diff --git a/include/linux/bit_spinlock.h b/include/linux/bit_spinlock.h
index bbc4730..713efc4 100644
--- a/include/linux/bit_spinlock.h
+++ b/include/linux/bit_spinlock.h
@@ -15,22 +15,17 @@
*/
static inline void bit_spin_lock(int bitnum, unsigned long *addr)
{
- /*
- * Assuming the lock is uncontended, this never enters
- * the body of the outer loop. If it is contended, then
- * within the inner loop a non-atomic test is used to
- * busywait with less bus contention for a good time to
- * attempt to acquire the lock bit.
- */
- preempt_disable();
#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
- while (unlikely(test_and_set_bit_lock(bitnum, addr))) {
- preempt_enable();
- do {
- cpu_relax();
- } while (test_bit(bitnum, addr));
+ while (1) {
+ smp_cond_load_relaxed(&addr[BIT_WORD(bitnum)],
+ !(VAL >> (bitnum & (BITS_PER_LONG-1))));
preempt_disable();
+ if (!test_and_set_bit_lock(bitnum, addr))
+ break;
+ preempt_enable();
}
+#else
+ preempt_disable();
#endif
__acquire(bitlock);
}
--
2.7.4
