Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 4d3b57da authored by Mark Rutland's avatar Mark Rutland Committed by Arnaldo Carvalho de Melo
Browse files

tools headers: Restore READ_ONCE() C++ compatibility 



Our userspace <linux/compiler.h> defines READ_ONCE() in a way that clang
doesn't like, as we have an anonymous union in which neither field is
initialized.

WRITE_ONCE() is fine since it initializes the __val field. For
READ_ONCE() we can keep clang and GCC happy with a dummy initialization
of the __c field, so let's do that.

At the same time, let's split READ_ONCE() and WRITE_ONCE() over several
lines for legibility, as we do in the in-kernel <linux/compiler.h>.

Reported-by: default avatarLi Zhijian <lizhijian@cn.fujitsu.com>
Reported-by: default avatarSandipan Das <sandipan@linux.vnet.ibm.com>
Tested-by: default avatarSandipan Das <sandipan@linux.vnet.ibm.com>
Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Fixes: 6aa7de05 ("locking/atomics: COCCINELLE/treewide: Convert trivial ACCESS_ONCE() patterns to READ_ONCE()/WRITE_ONCE()")
Link: http://lkml.kernel.org/r/20180404163445.16492-1-mark.rutland@arm.com


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 9dc9a95f

tools/include/linux/compiler.h

+15 −5
Original line number Diff line number Diff line
@@ -152,10 +152,20 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s 
 */



#define READ_ONCE(x)					\

	({ union { typeof(x) __val; char __c[1]; } __u; __read_once_size(&(x), __u.__c, sizeof(x)); __u.__val; })

({							\

	union { typeof(x) __val; char __c[1]; } __u =	\

		{ .__c = { 0 } };			\

	__read_once_size(&(x), __u.__c, sizeof(x));	\

	__u.__val;					\

})



#define WRITE_ONCE(x, val)				\

	({ union { typeof(x) __val; char __c[1]; } __u = { .__val = (val) }; __write_once_size(&(x), __u.__c, sizeof(x)); __u.__val; })

({							\

	union { typeof(x) __val; char __c[1]; } __u =	\

		{ .__val = (val) }; 			\

	__write_once_size(&(x), __u.__c, sizeof(x));	\

	__u.__val;					\

})





#ifndef __fallthrough