From c2bc66082e1048c7573d72e62f597bdc5ce13fea Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Tue, 24 Oct 2017 11:22:47 +0100 Subject: 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 Cc: Linus Torvalds Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1508840570-22169-3-git-send-email-will.deacon@arm.com Signed-off-by: Ingo Molnar --- include/linux/compiler.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/compiler.h') 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) -- cgit v1.2.3-59-g8ed1b