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authorMark Rutland <mark.rutland@arm.com>2017-10-23 14:07:29 -0700
committerIngo Molnar <mingo@kernel.org>2017-10-25 11:01:08 +0200
commit6aa7de059173a986114ac43b8f50b297a86f09a8 (patch)
tree77666afe795e022914ca26433d61686c694dc4fd /kernel/events
parentb03a0fe0c5e4b46dcd400d27395b124499554a71 (diff)
downloadlinux-6aa7de059173a986114ac43b8f50b297a86f09a8.tar.bz2
locking/atomics: COCCINELLE/treewide: Convert trivial ACCESS_ONCE() patterns to READ_ONCE()/WRITE_ONCE()
Please do not apply this to mainline directly, instead please re-run the coccinelle script shown below and apply its output. 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 harmful, and changing them results in churn. However, for some features, the read/write distinction is critical to correct operation. To distinguish these cases, separate read/write accessors must be used. This patch migrates (most) remaining ACCESS_ONCE() instances to {READ,WRITE}_ONCE(), using the following coccinelle script: ---- // Convert trivial ACCESS_ONCE() uses to equivalent READ_ONCE() and // WRITE_ONCE() // $ make coccicheck COCCI=/home/mark/once.cocci SPFLAGS="--include-headers" MODE=patch 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: Peter Zijlstra <peterz@infradead.org> 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/1508792849-3115-19-git-send-email-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/events')
-rw-r--r--kernel/events/core.c6
-rw-r--r--kernel/events/ring_buffer.c2
2 files changed, 4 insertions, 4 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 824a583079a1..8fd2f2d1358a 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1200,7 +1200,7 @@ perf_event_ctx_lock_nested(struct perf_event *event, int nesting)
again:
rcu_read_lock();
- ctx = ACCESS_ONCE(event->ctx);
+ ctx = READ_ONCE(event->ctx);
if (!atomic_inc_not_zero(&ctx->refcount)) {
rcu_read_unlock();
goto again;
@@ -5302,8 +5302,8 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
if (!rb)
goto aux_unlock;
- aux_offset = ACCESS_ONCE(rb->user_page->aux_offset);
- aux_size = ACCESS_ONCE(rb->user_page->aux_size);
+ aux_offset = READ_ONCE(rb->user_page->aux_offset);
+ aux_size = READ_ONCE(rb->user_page->aux_size);
if (aux_offset < perf_data_size(rb) + PAGE_SIZE)
goto aux_unlock;
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index f684d8e5fa2b..f3e37971c842 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -381,7 +381,7 @@ void *perf_aux_output_begin(struct perf_output_handle *handle,
* (B) <-> (C) ordering is still observed by the pmu driver.
*/
if (!rb->aux_overwrite) {
- aux_tail = ACCESS_ONCE(rb->user_page->aux_tail);
+ aux_tail = READ_ONCE(rb->user_page->aux_tail);
handle->wakeup = rb->aux_wakeup + rb->aux_watermark;
if (aux_head - aux_tail < perf_aux_size(rb))
handle->size = CIRC_SPACE(aux_head, aux_tail, perf_aux_size(rb));