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Merge branch 'perf-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

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* 'perf-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  ring_buffer: Off-by-one and duplicate events in ring_buffer_read_page
This commit is contained in:
Linus Torvalds 2010-12-28 15:54:24 -08:00
commit 6f7f41851c
1 changed files with 8 additions and 1 deletions
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9
kernel/trace/ring_buffer.c
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@ -3853,6 +3853,13 @@ int ring_buffer_read_page(struct ring_buffer *buffer,
/* Need to copy one event at a time */ /* Need to copy one event at a time */
do { do {
/* We need the size of one event, because
* rb_advance_reader only advances by one event,
* whereas rb_event_ts_length may include the size of
* one or two events.
* We have already ensured there's enough space if this
* is a time extend. */
size = rb_event_length(event);
memcpy(bpage->data + pos, rpage->data + rpos, size); memcpy(bpage->data + pos, rpage->data + rpos, size);
len -= size; len -= size;
@ -3867,7 +3874,7 @@ int ring_buffer_read_page(struct ring_buffer *buffer,
event = rb_reader_event(cpu_buffer); event = rb_reader_event(cpu_buffer);
/* Always keep the time extend and data together */ /* Always keep the time extend and data together */
size = rb_event_ts_length(event); size = rb_event_ts_length(event);
} while (len > size); } while (len >= size);
/* update bpage */ /* update bpage */
local_set(&bpage->commit, pos); local_set(&bpage->commit, pos);