From 4df714be4dcf40bfb0d4af0f851a6e1977afa02e Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Thu, 12 Oct 2017 13:20:48 +0100 Subject: locking/atomic: Add atomic_cond_read_acquire() smp_cond_load_acquire() provides a way to spin on a variable with acquire semantics until some conditional expression involving the variable is satisfied. Architectures such as arm64 can potentially enter a low-power state, waking up only when the value of the variable changes, which reduces the system impact of tight polling loops. This patch makes the same interface available to users of atomic_t, atomic64_t and atomic_long_t, rather than require messy accesses to the structure internals. Signed-off-by: Will Deacon Acked-by: Peter Zijlstra Cc: Boqun Feng Cc: Jeremy.Linton@arm.com Cc: Linus Torvalds Cc: Paul E. McKenney Cc: Thomas Gleixner Cc: Waiman Long Cc: linux-arm-kernel@lists.infradead.org Link: http://lkml.kernel.org/r/1507810851-306-3-git-send-email-will.deacon@arm.com Signed-off-by: Ingo Molnar --- include/linux/atomic.h | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'include/linux/atomic.h') diff --git a/include/linux/atomic.h b/include/linux/atomic.h index 40d6bfec0e0d..0aeb2b3f4578 100644 --- a/include/linux/atomic.h +++ b/include/linux/atomic.h @@ -653,6 +653,8 @@ static inline int atomic_dec_if_positive(atomic_t *v) } #endif +#define atomic_cond_read_acquire(v, c) smp_cond_load_acquire(&(v)->counter, (c)) + #ifdef CONFIG_GENERIC_ATOMIC64 #include #endif @@ -1072,6 +1074,8 @@ static inline long long atomic64_fetch_andnot_release(long long i, atomic64_t *v } #endif +#define atomic64_cond_read_acquire(v, c) smp_cond_load_acquire(&(v)->counter, (c)) + #include #endif /* _LINUX_ATOMIC_H */ -- cgit v1.2.3