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perf: Tighten (and fix) the grouping condition

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The fix from 9fc81d8742 ("perf: Fix events installation during
moving group") was incomplete in that it failed to recognise that
creating a group with events for different CPUs is semantically
broken -- they cannot be co-scheduled.

Furthermore, it leads to real breakage where, when we create an event
for CPU Y and then migrate it to form a group on CPU X, the code gets
confused where the counter is programmed -- triggered in practice
as well by me via the perf fuzzer.

Fix this by tightening the rules for creating groups. Only allow
grouping of counters that can be co-scheduled in the same context.
This means for the same task and/or the same cpu.

Fixes: 9fc81d8742 ("perf: Fix events installation during moving group")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20150123125834.090683288@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2015-01-23 11:19:48 +01:00 • committed by Ingo Molnar
commit c3c87e7704
2 changed files with 13 additions and 8 deletions
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6
include/linux/perf_event.h
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@ -450,11 +450,6 @@ struct perf_event {
#endif /* CONFIG_PERF_EVENTS */
};
enum perf_event_context_type {
task_context,
cpu_context,
};
/**
* struct perf_event_context - event context structure
*
@ -462,7 +457,6 @@ enum perf_event_context_type {
*/
struct perf_event_context {
struct pmu *pmu;
enum perf_event_context_type type;
/*
* Protect the states of the events in the list,
* nr_active, and the list: