Commit 74048f89 authored May 27, 2010 by Frederic Weisbecker Committed by Ingo Molnar May 31, 2010

perf_events: Fix unincremented buffer base on partial copy



If a sample size crosses to the next page boundary, the copy
will be made in more than one step. However we forget to advance
the source offset for the next copy, leading to unexpected double
copies that completely mess up the traces.

This fixes various kinds of bad traces that have irrelevant
data inside, as an example:

	geany-4979  [001]  5758.077775: sched_switch: prev_comm=! prev_pid=121
		prev_prio=0 prev_state=S|D|Z|X|x ==> next_comm= next_pid=7497072
		next_prio=0

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1274988898-5639-1-git-send-regression-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent 90151c35

kernel/perf_event.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -3064,6 +3064,7 @@ __always_inline void perf_output_copy(struct perf_output_handle *handle,

		len -= size;
		handle->addr += size;
		buf += size;
		handle->size -= size;
		if (!handle->size) {
		struct perf_mmap_data *data = handle->data;

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