ring-buffer: Make benchmark handle missed events

With the addition of the "missed events" flags that is stored in the
commit field of the ring buffer page, the ring_buffer_benchmark
was not updated to handle this. If events are missed, then the
missed events flag is set in the ring buffer page, the benchmark
will count that flag as part of the size of the page and will hit the BUG()
when it tries to read beyond the page.

The solution is simply to have the ring buffer benchmark mask off
the extra bits.

Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/ring_buffer_benchmark.c b/kernel/trace/ring_buffer_benchmark.c
index dc56556b55a24424bf4b0b10c79f00c39a8a86be..302f8a6146352a998f2730923598346196e84856 100644 (file)
--- a/kernel/trace/ring_buffer_benchmark.c
+++ b/kernel/trace/ring_buffer_benchmark.c
@@ -113,7 +113,8 @@ static enum event_status read_page(int cpu)
        ret = ring_buffer_read_page(buffer, &bpage, PAGE_SIZE, cpu, 1);
        if (ret >= 0) {
                rpage = bpage;
-               commit = local_read(&rpage->commit);
+               /* The commit may have missed event flags set, clear them */
+               commit = local_read(&rpage->commit) & 0xfffff;
                for (i = 0; i < commit && !kill_test; i += inc) {
 
                        if (i >= (PAGE_SIZE - offsetof(struct rb_page, data))) {