perf tools: Prefer to use a cpu-wide event for probing CLOEXEC
authorAdrian Hunter <adrian.hunter@intel.com>
Tue, 12 Aug 2014 15:04:31 +0000 (18:04 +0300)
committerArnaldo Carvalho de Melo <acme@redhat.com>
Wed, 13 Aug 2014 19:24:13 +0000 (16:24 -0300)
commitf6edb53c4993ffe92ce521fb449d1c146cea6ec2
tree49f920dcfeeb5e722d62da942d838bc6a0a2f06c
parent46ec69add5df60310147ce3ce01a662053d82a1e
perf tools: Prefer to use a cpu-wide event for probing CLOEXEC

When doing a system-wide trace with Intel PT, the jump label set up as a
result of probing CLOEXEC gets reset while the trace is running.  That
causes an Intel PT decoding error because the object code (obtained from
/proc/kcore) does not match the running code at that point.  While we
can't expect there never to be jump label changes, we can avoid cases
that the perf tool itself creates.

The problem is avoided by first trying a cpu-wide event (pid = -1) for
probing the PERF_FLAG_FD_CLOEXEC flag and falling back to an event for
the current process (pid = 0).

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1407855871-15024-5-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
tools/perf/util/cloexec.c