Messages in this thread Patch in this message | | | From | Gao Xiang <> | Subject | [RFC PATCH] bit_spinlock: introduce smp_cond_load_relaxed | Date | Sat, 13 Oct 2018 14:47:29 +0800 |
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It is better to use smp_cond_load_relaxed instead of busy waiting for bit_spinlock.
Signed-off-by: Gao Xiang <hsiangkao@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
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