[PATCH 3.10 278/319] kernel: Change ASSIGN_ONCE(val, x) to WRITE_ONCE(x, val)

Willy Tarreau
2017-02-05T19:29:04Z

From: Christian Borntraeger <borntraeger@de.ibm.com>

commit 43239cbe79fc369f5d2160bd7f69e28b5c50a58c upstream.

Feedback has shown that WRITE_ONCE(x, val) is easier to use than
ASSIGN_ONCE(val,x).
There are no in-tree users yet, so lets change it for 3.19.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
[wt: backported only for next patch]

Signed-off-by: Willy Tarreau <w@1wt.eu>
---
include/linux/compiler.h | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 9df1978..236a4e3 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -208,7 +208,7 @@ static __always_inline void __read_once_size(volatile void *p, void *res, int si
}
}

-static __always_inline void __assign_once_size(volatile void *p, void *res, int size)
+static __always_inline void __write_once_size(volatile void *p, void *res, int size)
{
switch (size) {
case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
@@ -228,15 +228,15 @@ static __always_inline void __assign_once_size(volatile void *p, void *res, int
/*
* Prevent the compiler from merging or refetching reads or writes. The
* compiler is also forbidden from reordering successive instances of
- * READ_ONCE, ASSIGN_ONCE and ACCESS_ONCE (see below), but only when the
+ * READ_ONCE, WRITE_ONCE and ACCESS_ONCE (see below), but only when the
* compiler is aware of some particular ordering. One way to make the
* compiler aware of ordering is to put the two invocations of READ_ONCE,
- * ASSIGN_ONCE or ACCESS_ONCE() in different C statements.
+ * WRITE_ONCE or ACCESS_ONCE() in different C statements.
*
* In contrast to ACCESS_ONCE these two macros will also work on aggregate
* data types like structs or unions. If the size of the accessed data
* type exceeds the word size of the machine (e.g., 32 bits or 64 bits)
- * READ_ONCE() and ASSIGN_ONCE() will fall back to memcpy and print a
+ * READ_ONCE() and WRITE_ONCE() will fall back to memcpy and print a
* compile-time warning.
*
* Their two major use cases are: (1) Mediating communication between
@@ -250,8 +250,8 @@ 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; })

-#define ASSIGN_ONCE(val, x) \
- ({ typeof(x) __val; __val = val; __assign_once_size(&x, &__val, sizeof(__val)); __val; })
+#define WRITE_ONCE(x, val) \
+ ({ typeof(x) __val; __val = val; __write_once_size(&x, &__val, sizeof(__val)); __val; })

#endif /* __KERNEL__ */

--
2.8.0.rc2.1.gbe9624a