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author | Mark Rutland <mark.rutland@arm.com> | 2017-10-23 14:07:29 -0700 |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2017-10-25 11:01:08 +0200 |
commit | 6aa7de059173a986114ac43b8f50b297a86f09a8 (patch) | |
tree | 77666afe795e022914ca26433d61686c694dc4fd /kernel/events | |
parent | b03a0fe0c5e4b46dcd400d27395b124499554a71 (diff) | |
download | linux-stable-6aa7de059173a986114ac43b8f50b297a86f09a8.tar.gz linux-stable-6aa7de059173a986114ac43b8f50b297a86f09a8.tar.bz2 linux-stable-6aa7de059173a986114ac43b8f50b297a86f09a8.zip |
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.c | 6 | ||||
-rw-r--r-- | kernel/events/ring_buffer.c | 2 |
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)); |