For several reasons, it is desirable to use {READ,WRITE}_ONCE() in
preference to ACCESS_ONCE(), and new code is expected to use one of the
former. So far, there's been no reason to change most existing uses of
ACCESS_ONCE(), as these aren't currently harmful.
However, for some features it is necessary to instrument reads and
writes separately, which is not possible with ACCESS_ONCE(). This
distinction is critical to correct operation.
It's possible to transform the bulk of kernel code using the Coccinelle
script below. However, this doesn't handle comments, leaving references
to ACCESS_ONCE() instances which have been removed. As a preparatory
step, this patch converts the DVB ringbuffer code and comments to use
{READ,WRITE}_ONCE() consistently.
----
virtual patch
@ depends on patch @
expression E1, E2;
@@
- ACCESS_ONCE(E1) = E2
+ WRITE_ONCE(E1, E2)
@ depends on patch @
expression E;
@@
- ACCESS_ONCE(E)
+ READ_ONCE(E)
----
Signed-off-by: Mark Rutland <mark.rutl...@arm.com>
Cc: Mauro Carvalho Chehab <mche...@kernel.org>
Cc: Sakari Ailus <sakari.ai...@linux.intel.com>
---
drivers/media/dvb-core/dvb_ringbuffer.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/drivers/media/dvb-core/dvb_ringbuffer.c
b/drivers/media/dvb-core/dvb_ringbuffer.c
index 2322af1..5301162 100644
--- a/drivers/media/dvb-core/dvb_ringbuffer.c
+++ b/drivers/media/dvb-core/dvb_ringbuffer.c
@@ -66,12 +66,12 @@ ssize_t dvb_ringbuffer_free(struct dvb_ringbuffer *rbuf)
{
ssize_t free;
- /* ACCESS_ONCE() to load read pointer on writer side
+ /* READ_ONCE() to load read pointer on writer side
* this pairs with smp_store_release() in dvb_ringbuffer_read(),
* dvb_ringbuffer_read_user(), dvb_ringbuffer_flush(),
* or dvb_ringbuffer_reset()
*/
- free = ACCESS_ONCE(rbuf->pread) - rbuf->pwrite;
+ free = READ_ONCE(rbuf->pread) - rbuf->pwrite;
if (free <= 0)
free += rbuf->size;
return free-1;
@@ -143,7 +143,7 @@ ssize_t dvb_ringbuffer_read_user(struct dvb_ringbuffer
*rbuf, u8 __user *buf, si
todo -= split;
/* smp_store_release() for read pointer update to ensure
* that buf is not overwritten until read is complete,
- * this pairs with ACCESS_ONCE() in dvb_ringbuffer_free()
+ * this pairs with READ_ONCE() in dvb_ringbuffer_free()
*/
smp_store_release(&rbuf->pread, 0);
}
@@ -168,7 +168,7 @@ void dvb_ringbuffer_read(struct dvb_ringbuffer *rbuf, u8
*buf, size_t len)
todo -= split;
/* smp_store_release() for read pointer update to ensure
* that buf is not overwritten until read is complete,
- * this pairs with ACCESS_ONCE() in dvb_ringbuffer_free()
+ * this pairs with READ_ONCE() in dvb_ringbuffer_free()
*/
smp_store_release(&rbuf->pread, 0);
}
--
1.9.1
