perf: Ensure that IOC_OUTPUT isn't used to create multi-writer buffers (0f139300) · Commits · 戴 / test

Since we want to ensure buffers only have a single writer, we must avoid creating one with multiple. Signed-off-by:

Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Steven Rostedt <rostedt@goodmis.org> LKML-Reference: <20100521090710.528215873@chello.nl> Signed-off-by:

Ingo Molnar <mingo@elte.hu>

kernel/perf_event.c

+19 −0

Original line number	Diff line number	Diff line
		@@ -4920,6 +4920,13 @@ static int perf_event_set_output(struct perf_event *event, int output_fd)
		int fput_needed = 0;
		int ret = -EINVAL;

		/*
		* Don't allow output of inherited per-task events. This would
		* create performance issues due to cross cpu access.
		*/
		if (event->cpu == -1 && event->attr.inherit)
		return -EINVAL;

		if (!output_fd)
		goto set;

		@@ -4940,6 +4947,18 @@ static int perf_event_set_output(struct perf_event *event, int output_fd)
		if (event->data)
		goto out;

		/*
		* Don't allow cross-cpu buffers
		*/
		if (output_event->cpu != event->cpu)
		goto out;

		/*
		* If its not a per-cpu buffer, it must be the same task.
		*/
		if (output_event->cpu == -1 && output_event->ctx != event->ctx)
		goto out;

		atomic_long_inc(&output_file->f_count);

		set:

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