Eric B Munson 7f310a5d4e perf_event: Fix broken calc_timer_values() ... We detected a serious issue with PERF_SAMPLE_READ and timing information when events were being multiplexing. Samples would have time_running > time_enabled. That was easy to reproduce with a libpfm4 example (ran 3 times to cause multiplexing on Core 2): $ syst_smpl -e uops_retired:freq=1 & $ syst_smpl -e uops_retired:freq=1 & $ syst_smpl -e uops_retired:freq=1 & IIP:0x0000000040062d ... PERIOD:2355332948 ENA=40144625315 RUN=60014875184 syst_smpl: WARNING: time_running > time_enabled 63277537998 uops_retired:freq=1 , scaled The bug was not present in kernel up to (and including) 3.0. It turns out the bug was introduced by the following commit: commit c479429591 events: Move lockless timer calculation into helper function The parameters of the function got reversed yet the call sites were not updated to reflect the change. That lead to time_running and time_enabled being swapped. That had no effect when there was no multiplexing because in that case time_running = time_enabled but it would show up in any other scenario. Signed-off-by: Stephane Eranian <eranian@google.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/20110829124112.GA4828@quad Signed-off-by: Ingo Molnar <mingo@elte.hu>		2011-08-31 15:56:29 +02:00
..
core.c	perf_event: Fix broken calc_timer_values()	2011-08-31 15:56:29 +02:00
hw_breakpoint.c	perf: Add context field to perf_event	2011-07-01 11:06:38 +02:00
internal.h	perf: Remove the nmi parameter from the swevent and overflow interface	2011-07-01 11:06:35 +02:00
Makefile	perf: Split up buffer handling from core code	2011-06-09 12:57:54 +02:00
ring_buffer.c	perf: Remove the perf_output_begin(.sample) argument	2011-07-01 11:06:35 +02:00