The commit is pushed to "branch-rh7-3.10.0-229.7.2.vz7.9.x-ovz" and will appear
at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-229.7.2.vz7.9.10
------>
commit 38904c408bdbf049edeea5ffc529c248930164ec
Author: Linus Torvalds <torva...@linux-foundation.org>
Date: Wed Nov 18 13:23:13 2015 +0400
ms/kernel: make READ_ONCE() valid on const arguments
The use of READ_ONCE() causes lots of warnings witht he pending paravirt
spinlock fixes, because those ends up having passing a member to a
'const' structure to READ_ONCE().
There should certainly be nothing wrong with using READ_ONCE() with a
const source, but the helper function __read_once_size() would cause
warnings because it would drop the 'const' qualifier, but also because
the destination would be marked 'const' too due to the use of 'typeof'.
Use a union of types in READ_ONCE() to avoid this issue.
Also make sure to use parenthesis around the macro arguments to avoid
possible operator precedence issues.
Tested-by: Ingo Molnar <mi...@kernel.org>
Cc: Christian Borntraeger <borntrae...@de.ibm.com>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
(cherry picked from commit dd36929720f40f17685e841ae0d4c581c165ea60)
Signed-off-by: Andrey Ryabinin <aryabi...@virtuozzo.com>
Signed-off-by: Andrey Ryabinin <aryabi...@virtuozzo.com>
---
include/linux/compiler.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 0737107..39fe1dc 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -187,7 +187,7 @@ static __always_inline void
data_access_exceeds_word_size(void)
{
}
-static __always_inline void __read_once_size(volatile void *p, void *res, int
size)
+static __always_inline void __read_once_size(const volatile void *p, void
*res, int size)
{
switch (size) {
case 1: *(__u8 *)res = *(volatile __u8 *)p; break;
@@ -244,7 +244,7 @@ static __always_inline void __assign_once_size(volatile
void *p, void *res, int
*/
#define READ_ONCE(x) \
- ({ typeof(x) __val; __read_once_size(&x, &__val, sizeof(__val)); __val;
})
+ ({ union { typeof(x) __val; char __c[1]; } __u; __read_once_size(&(x),
__u.__c, sizeof(x)); __u.__val; })
#define ASSIGN_ONCE(val, x) \
({ typeof(x) __val; __val = val; __assign_once_size(&x, &__val,
sizeof(__val)); __val; })
_______________________________________________
Devel mailing list
Devel@openvz.org
https://lists.openvz.org/mailman/listinfo/devel
