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| author | Peter Zijlstra <peterz@infradead.org> | 2015-09-18 14:22:52 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-09-23 10:54:29 +0300 |
| commit | e3e72ab80a3fac0b88e07d358a2c75724ccd66b4 (patch) | |
| tree | 3cc1b2f6fbe8ca8d3649d95d14f7c093cea11480 /include/linux | |
| parent | 62e8a3258bda118f24ff462fe04cfbe75b8189b5 (diff) | |
| download | linux-e3e72ab80a3fac0b88e07d358a2c75724ccd66b4.tar.xz | |
atomic: Implement atomic_read_ctrl()
Provide atomic_read_ctrl() to mirror READ_ONCE_CTRL(), such that we can
more conveniently use atomics in control dependencies.
Since we can assume atomic_read() implies a READ_ONCE(), we must only
emit an extra smp_read_barrier_depends() in order to upgrade to
READ_ONCE_CTRL() semantics.
Requested-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Cc: oleg@redhat.com
Link: http://lkml.kernel.org/r/20150918115637.GM3604@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/atomic.h | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/include/linux/atomic.h b/include/linux/atomic.h index 29dafa184aeb..e326469bb9d6 100644 --- a/include/linux/atomic.h +++ b/include/linux/atomic.h @@ -4,6 +4,15 @@ #include <asm/atomic.h> #include <asm/barrier.h> +#ifndef atomic_read_ctrl +static inline int atomic_read_ctrl(const atomic_t *v) +{ + int val = atomic_read(v); + smp_read_barrier_depends(); /* Enforce control dependency. */ + return val; +} +#endif + /* * Relaxed variants of xchg, cmpxchg and some atomic operations. * @@ -455,6 +464,15 @@ static inline int atomic_dec_if_positive(atomic_t *v) #include <asm-generic/atomic64.h> #endif +#ifndef atomic64_read_ctrl +static inline long long atomic64_read_ctrl(const atomic64_t *v) +{ + long long val = atomic64_read(v); + smp_read_barrier_depends(); /* Enforce control dependency. */ + return val; +} +#endif + #ifndef atomic64_andnot static inline void atomic64_andnot(long long i, atomic64_t *v) { |