On 18/09/15 18:29, Arnaldo Carvalho de Melo wrote: > 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?
Yes > > - 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/
