4.14-stable review patch. If anyone has any objections, please let me know.
------------------
From: Will Deacon will.deacon@arm.com
commit c2bc66082e1048c7573d72e62f597bdc5ce13fea upstream.
[ 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.c... Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- include/linux/compiler.h | 1 + 1 file changed, 1 insertion(+)
--- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -341,6 +341,7 @@ static __always_inline void __write_once __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)