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authorMark Rutland <mark.rutland@arm.com>2017-10-23 14:07:16 -0700
committerIngo Molnar <mingo@kernel.org>2017-10-25 11:00:58 +0200
commit24fbd6e04e4e4793ec9dd9c2e007b0b38d2ec3ab (patch)
treea299aed0a96b248ca95f280041b2694762901325
parentfd7048adb7a5f3c44154675e0e128fe0f2e16bef (diff)
locking/atomics, media/dvb_ringbuffer: Convert ACCESS_ONCE() to READ_ONCE()/WRITE_ONCE()
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.rutland@arm.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mauro Carvalho Chehab <mchehab@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sakari Ailus <sakari.ailus@linux.intel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: davem@davemloft.net Cc: linux-arch@vger.kernel.org Cc: mpe@ellerman.id.au Cc: shuah@kernel.org Cc: snitzer@redhat.com Cc: thor.thayer@linux.intel.com Cc: tj@kernel.org Cc: viro@zeniv.linux.org.uk Cc: will.deacon@arm.com Link: http://lkml.kernel.org/r/1508792849-3115-6-git-send-email-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--drivers/media/dvb-core/dvb_ringbuffer.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/drivers/media/dvb-core/dvb_ringbuffer.c b/drivers/media/dvb-core/dvb_ringbuffer.c
index 2322af1b8742..53011629c9ad 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);
}