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Commit 2ab346cf authored by Will Deacon's avatar Will Deacon Committed by Ingo Molnar
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perf/aux: Make aux_{head,wakeup} ring_buffer members long 



The aux_head and aux_wakeup members of struct ring_buffer are defined
using the local_t type, despite the fact that they are only accessed via
the perf_aux_output_*() functions, which cannot race with each other for a
given ring buffer.

This patch changes the type of the members to long, so we can avoid
using the local_*() API where it isn't needed.

Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/1502900297-21839-1-git-send-email-will.deacon@arm.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 290d9bf2

kernel/events/internal.h

+2 −2
Original line number Diff line number Diff line
@@ -38,9 +38,9 @@ struct ring_buffer { 
	struct user_struct		*mmap_user;



	/* AUX area */

	local_t				aux_head;

	long				aux_head;

	local_t				aux_nest;

	local_t				aux_wakeup;

	long				aux_wakeup;

	unsigned long			aux_pgoff;

	int				aux_nr_pages;

	int				aux_overwrite;

kernel/events/ring_buffer.c

+14 −17
Original line number Diff line number Diff line
@@ -367,7 +367,7 @@ void *perf_aux_output_begin(struct perf_output_handle *handle, 
	if (WARN_ON_ONCE(local_xchg(&rb->aux_nest, 1)))

		goto err_put;



	aux_head = local_read(&rb->aux_head);

	aux_head = rb->aux_head;



	handle->rb = rb;

	handle->event = event;
@@ -382,7 +382,7 @@ void *perf_aux_output_begin(struct perf_output_handle *handle, 
	 */

	if (!rb->aux_overwrite) {

		aux_tail = ACCESS_ONCE(rb->user_page->aux_tail);

		handle->wakeup = local_read(&rb->aux_wakeup) + rb->aux_watermark;

		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));
@@ -433,12 +433,12 @@ void perf_aux_output_end(struct perf_output_handle *handle, unsigned long size) 
		handle->aux_flags |= PERF_AUX_FLAG_OVERWRITE;



		aux_head = handle->head;

		local_set(&rb->aux_head, aux_head);

		rb->aux_head = aux_head;

	} else {

		handle->aux_flags &= ~PERF_AUX_FLAG_OVERWRITE;



		aux_head = local_read(&rb->aux_head);

		local_add(size, &rb->aux_head);

		aux_head = rb->aux_head;

		rb->aux_head += size;

	}



	if (size || handle->aux_flags) {
@@ -450,11 +450,10 @@ void perf_aux_output_end(struct perf_output_handle *handle, unsigned long size) 
		                     handle->aux_flags);

	}



	aux_head = rb->user_page->aux_head = local_read(&rb->aux_head);



	if (aux_head - local_read(&rb->aux_wakeup) >= rb->aux_watermark) {

	rb->user_page->aux_head = rb->aux_head;

	if (rb->aux_head - rb->aux_wakeup >= rb->aux_watermark) {

		wakeup = true;

		local_add(rb->aux_watermark, &rb->aux_wakeup);

		rb->aux_wakeup += rb->aux_watermark;

	}



	if (wakeup) {
@@ -478,22 +477,20 @@ void perf_aux_output_end(struct perf_output_handle *handle, unsigned long size) 
int perf_aux_output_skip(struct perf_output_handle *handle, unsigned long size)

{

	struct ring_buffer *rb = handle->rb;

	unsigned long aux_head;



	if (size > handle->size)

		return -ENOSPC;



	local_add(size, &rb->aux_head);

	rb->aux_head += size;



	aux_head = rb->user_page->aux_head = local_read(&rb->aux_head);

	if (aux_head - local_read(&rb->aux_wakeup) >= rb->aux_watermark) {

	rb->user_page->aux_head = rb->aux_head;

	if (rb->aux_head - rb->aux_wakeup >= rb->aux_watermark) {

		perf_output_wakeup(handle);

		local_add(rb->aux_watermark, &rb->aux_wakeup);

		handle->wakeup = local_read(&rb->aux_wakeup) +

				 rb->aux_watermark;

		rb->aux_wakeup += rb->aux_watermark;

		handle->wakeup = rb->aux_wakeup + rb->aux_watermark;

	}



	handle->head = aux_head;

	handle->head = rb->aux_head;

	handle->size -= size;



	return 0;