From e603dc15072c7fec0ae263597e6dabc3bb4c5c5b Mon Sep 17 00:00:00 2001 From: Arnaldo Carvalho de Melo Date: Mon, 21 Feb 2011 16:05:50 -0300 Subject: [PATCH] perf evsel: Fix inverted test for fixing up attr.inherit flag 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 Cc: Frederic Weisbecker Cc: Ingo Molnar Cc: Mike Galbraith Cc: Paul Mackerras Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Tom Zanussi LKML-Reference: Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/evsel.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c index 63cadaf..8083d51 100644 --- a/tools/perf/util/evsel.c +++ b/tools/perf/util/evsel.c @@ -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++) { -- 2.7.4