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authorWill Deacon <will.deacon@arm.com>2017-10-24 11:22:50 +0100
committerIngo Molnar <mingo@kernel.org>2017-10-24 13:17:34 +0200
commit5a8897cc7631fa544d079c443800f4420d1b173f (patch)
tree85ebb227577173a8744d47fb220379651aa4235b /arch
parent59ecbbe7b31cd2d86ff9a9f461a00f7e7533aedc (diff)
locking/atomics/alpha: Add smp_read_barrier_depends() to _release()/_relaxed() atomics
As part of the fight against smp_read_barrier_depends(), we require dependency ordering to be preserved when a dependency is headed by a load performed using an atomic operation. This patch adds smp_read_barrier_depends() to the _release() and _relaxed() atomics on alpha, which otherwise lack anything to enforce dependency ordering. Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1508840570-22169-6-git-send-email-will.deacon@arm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/alpha/include/asm/atomic.h13
1 files changed, 13 insertions, 0 deletions
diff --git a/arch/alpha/include/asm/atomic.h b/arch/alpha/include/asm/atomic.h
index 498933a7df97..16961a3f45ba 100644
--- a/arch/alpha/include/asm/atomic.h
+++ b/arch/alpha/include/asm/atomic.h
@@ -13,6 +13,15 @@
* than regular operations.
*/
+/*
+ * To ensure dependency ordering is preserved for the _relaxed and
+ * _release atomics, an smp_read_barrier_depends() is unconditionally
+ * inserted into the _relaxed variants, which are used to build the
+ * barriered versions. To avoid redundant back-to-back fences, we can
+ * define the _acquire and _fence versions explicitly.
+ */
+#define __atomic_op_acquire(op, args...) op##_relaxed(args)
+#define __atomic_op_fence __atomic_op_release
#define ATOMIC_INIT(i) { (i) }
#define ATOMIC64_INIT(i) { (i) }
@@ -60,6 +69,7 @@ static inline int atomic_##op##_return_relaxed(int i, atomic_t *v) \
".previous" \
:"=&r" (temp), "=m" (v->counter), "=&r" (result) \
:"Ir" (i), "m" (v->counter) : "memory"); \
+ smp_read_barrier_depends(); \
return result; \
}
@@ -77,6 +87,7 @@ static inline int atomic_fetch_##op##_relaxed(int i, atomic_t *v) \
".previous" \
:"=&r" (temp), "=m" (v->counter), "=&r" (result) \
:"Ir" (i), "m" (v->counter) : "memory"); \
+ smp_read_barrier_depends(); \
return result; \
}
@@ -111,6 +122,7 @@ static __inline__ long atomic64_##op##_return_relaxed(long i, atomic64_t * v) \
".previous" \
:"=&r" (temp), "=m" (v->counter), "=&r" (result) \
:"Ir" (i), "m" (v->counter) : "memory"); \
+ smp_read_barrier_depends(); \
return result; \
}
@@ -128,6 +140,7 @@ static __inline__ long atomic64_fetch_##op##_relaxed(long i, atomic64_t * v) \
".previous" \
:"=&r" (temp), "=m" (v->counter), "=&r" (result) \
:"Ir" (i), "m" (v->counter) : "memory"); \
+ smp_read_barrier_depends(); \
return result; \
}