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perf evsel: Fix inverted test for fixing up attr.inherit flag

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The kernel refuses mmapping an event with the inherit flag set for
something that is systemwide (cpu == -1), and the evsel layer got this
reversed at some point, fix it.

The symtom was that the --pid and --tid parameters for 'perf record' and
'perf top' returned with -EINVAL, like:

 # /tmp/build-perf/perf record -v -fo/tmp/perf.data -p 1042
   Warning:  ... trying to fall back to cpu-clock-ticks

   Fatal: failed to mmap with 22 (Invalid argument)

Reported-by: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Arnaldo Carvalho de Melo 2011-02-21 16:05:50 -03:00
parent fbee632d0c
commit e603dc1507
1 changed files with 13 additions and 2 deletions
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15
tools/perf/util/evsel.c
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@ -179,8 +179,19 @@ static int __perf_evsel__open(struct perf_evsel *evsel, struct cpu_map *cpus,
for (cpu = 0; cpu < cpus->nr; cpu++) {
int group_fd = -1;
evsel->attr.inherit = (cpus->map[cpu] < 0) && inherit;
/*
* Don't allow mmap() of inherited per-task counters. This
* would create a performance issue due to all children writing
* to the same buffer.
*
* FIXME:
* Proper fix is not to pass 'inherit' to perf_evsel__open*,
* but a 'flags' parameter, with 'group' folded there as well,
* then introduce a PERF_O_{MMAP,GROUP,INHERIT} enum, and if
* O_MMAP is set, emit a warning if cpu < 0 and O_INHERIT is
* set. Lets go for the minimal fix first tho.
*/
evsel->attr.inherit = (cpus->map[cpu] >= 0) && inherit;
for (thread = 0; thread < threads->nr; thread++) {