Em Fri, Sep 18, 2015 at 04:18:51PM +0100, Mark Rutland escreveu: > On Fri, Sep 18, 2015 at 04:00:18PM +0100, Arnaldo Carvalho de Melo wrote: > > After applying your patch it works, had to tweak the commit log to avoid > > starting lines with ---, breaks git scripts, also added a commiter log, > > check it, patch is below, after the one I used to not process any > > samples. > Sorry for the '---' problem, I'll bear that in mind in future. > Your commit log looks fine, though I'm slightly confused by the > Reported-by line -- did you mean to add that?
Sorry, I mean Tested-by:, will replace, guess i can replace the one for Adrian from Cc: to Tested-by too, right? - Arnaldo > Mark. > > > commit dd486ec4aa33cfca2fd912ef501d49909005de79 > > Author: Mark Rutland <mark.rutl...@arm.com> > > Date: Wed Sep 16 18:18:49 2015 +0100 > > > > perf record: Avoid infinite loop at buildid processing with no samples > > > > If a session contains no events, we can get stuck in an infinite loop in > > __perf_session__process_events, with a non-zero file_size and > > data_offset, but > > a zero data_size. > > > > In this case, we can mmap the entirety of the file (consisting of the > > file and > > attribute headers), and fetch_mmaped_event will correctly refuse to > > read any > > (unmapped and non-existent) event headers. This causes > > __perf_session__process_events to unmap the file and retry with the > > exact same > > parameters, getting stuck in an infinite loop. > > > > This has been observed to result in an exit-time hang when counting > > rare/unschedulable events with perf record, and can be triggered > > artificially > > with the script below: > > > > ---- > > #!/bin/sh > > printf "REPRO: launching perf\n"; > > ./perf record -e software/config=9/ sleep 1 & > > PERF_PID=$!; > > sleep 0.002; > > kill -2 $PERF_PID; > > printf "REPRO: waiting for perf (%d) to exit...\n" "$PERF_PID"; > > wait $PERF_PID; > > printf "REPRO: perf exited\n"; > > ---- > > > > To avoid this, have __perf_session__process_events bail out early when > > the file has no data (i.e. it has no events). > > > > Commiter note: > > > > I only managed to reproduce this when setting > > /proc/sys/kernel/kptr_restrict to '1' and changing the code to > > purposefully not process any samples and no synthesized samples, i.e. > > kptr_restrict prevents 'record' from synthesizing the kernel mmaps for > > vmlinux + modules and since it is a workload started from perf, we don't > > synthesize mmap/comm records for existing threads. > > > > Adrian Hunter managed to reproduce it in his environment tho. > > > > Reported-by: Arnaldo Carvalho de Melo <a...@kernel.org> > > Signed-off-by: Mark Rutland <mark.rutl...@arm.com> > > Cc: Adrian Hunter <adrian.hun...@intel.com> > > Cc: Jiri Olsa <jo...@redhat.com> > > Cc: Peter Zijlstra <pet...@infradead.org> > > Link: > > http://lkml.kernel.org/r/1442423929-12253-1-git-send-email-mark.rutl...@arm.com > > Signed-off-by: Arnaldo Carvalho de Melo <a...@redhat.com> > > > > diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c > > index 8a4537ee9bc3..fc3f7c922f99 100644 > > --- a/tools/perf/util/session.c > > +++ b/tools/perf/util/session.c > > @@ -1580,7 +1580,10 @@ static int __perf_session__process_events(struct > > perf_session *session, > > file_offset = page_offset; > > head = data_offset - page_offset; > > > > - if (data_size && (data_offset + data_size < file_size)) > > + if (data_size == 0) > > + goto out; > > + > > + if (data_offset + data_size < file_size) > > file_size = data_offset + data_size; > > > > ui_progress__init(&prog, file_size, "Processing events..."); > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
