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authorWill Deacon <will.deacon@arm.com>2017-10-24 11:22:47 +0100
committerIngo Molnar <mingo@kernel.org>2017-12-17 13:57:01 +0100
commitc2bc66082e1048c7573d72e62f597bdc5ce13fea (patch)
tree6f2e6ad4fb90064a5b862a7591584ed5aa7884cf
parentab95477e7cb35557ecfc837687007b646bab9a9f (diff)
downloadlinux-sh-c2bc66082e1048c7573d72e62f597bdc5ce13fea.tar.gz
locking/barriers: Add implicit smp_read_barrier_depends() to READ_ONCE()
[ Note, this is a Git cherry-pick of the following commit: 76ebbe78f739 ("locking/barriers: Add implicit smp_read_barrier_depends() to READ_ONCE()") ... for easier x86 PTI code testing and back-porting. ] 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>
-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 202710420d6d..712cd8bb00b4 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -341,6 +341,7 @@ 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)