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linux-next/kernel/events
Vince Weaver 4ec8363dfc perf_events: Fix perf buffer watermark setting
Since 2.6.36 (specifically commit d57e34fdd6 ("perf: Simplify the
ring-buffer logic: make perf_buffer_alloc() do everything needed"),
the perf_buffer_init_code() has been mis-setting the buffer watermark
if perf_event_attr.wakeup_events has a non-zero value.

This is because perf_event_attr.wakeup_events is a union with
perf_event_attr.wakeup_watermark.

This commit re-enables the check for perf_event_attr.watermark being
set before continuing with setting a non-default watermark.

This bug is most noticable when you are trying to use PERF_IOC_REFRESH
with a value larger than one and perf_event_attr.wakeup_events is set to
one.  In this case the buffer watermark will be set to 1 and you will
get extraneous POLL_IN overflows rather than POLL_HUP as expected.

[ avoid using attr.wakeup_events when attr.watermark is set ]

Signed-off-by: Vince Weaver <vweaver1@eecs.utk.edu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: <stable@kernel.org>
Link: http://lkml.kernel.org/r/alpine.DEB.2.00.1106011506390.5384@cl320.eecs.utk.edu
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-07-01 11:06:32 +02:00
..
core.c perf_events: Fix perf buffer watermark setting 2011-07-01 11:06:32 +02:00
hw_breakpoint.c hw breakpoints: Move to kernel/events/ 2011-05-03 15:26:43 +02:00
internal.h perf: Split up buffer handling from core code 2011-06-09 12:57:54 +02:00
Makefile perf: Split up buffer handling from core code 2011-06-09 12:57:54 +02:00
ring_buffer.c perf_events: Fix perf buffer watermark setting 2011-07-01 11:06:32 +02:00