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authorWill Deacon <will.deacon@arm.com>2017-10-24 11:22:47 +0100
committerIngo Molnar <mingo@kernel.org>2017-10-24 13:17:32 +0200
commit76ebbe78f7390aee075a7f3768af197ded1bdfbb (patch)
tree531d3794d965b8e4e8107d8dbd1b124cbf3dbca5 /include/linux/compiler.h
parentd15155824c5014803d91b829736d249c500bdda6 (diff)
locking/barriers: Add implicit smp_read_barrier_depends() to READ_ONCE()
In preparation for the removal of lockless_dereference(), which is the same as READ_ONCE() on all architectures other than Alpha, add an implicit smp_read_barrier_depends() to READ_ONCE() so that it can be used to head dependency chains on all architectures. Signed-off-by: Will Deacon <will.deacon@arm.com> 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> Link: http://lkml.kernel.org/r/1508840570-22169-3-git-send-email-will.deacon@arm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include/linux/compiler.h')
-rw-r--r--include/linux/compiler.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 08083186e54f..7d7b77da9716 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -242,6 +242,7 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
__read_once_size(&(x), __u.__c, sizeof(x)); \
else \
__read_once_size_nocheck(&(x), __u.__c, sizeof(x)); \
+ smp_read_barrier_depends(); /* Enforce dependency ordering from x */ \
__u.__val; \
})
#define READ_ONCE(x) __READ_ONCE(x, 1)