Em Wed, Sep 16, 2015 at 06:18:49PM +0100, Mark Rutland escreveu:
> 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";
> ----
So, I run it here, without this patch, and get:
[root@zoo ~]# time ./repro.sh
REPRO: launching perf
REPRO: waiting for perf (766) to exit...
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.015 MB perf.data ]
REPRO: perf exited
real 0m1.060s
user 0m0.018s
sys 0m0.037s
[root@zoo ~]# perf report --stdio
Error:
The perf.data file has no samples!
# To display the perf.data header info, please use
# --header/--header-only options.
#
[root@zoo ~]# perf evlist -v
software/config=9/: type: 1, size: 112, config: 0x9, { sample_period,
sample_freq }: 4000, sample_type: IP|TID|TIME|PERIOD, disabled: 1,
inherit: 1, mmap: 1, comm: 1, freq: 1, enable_on_exec: 1, task: 1,
sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1
[root@zoo ~]#
What am I doing wrong? Trying to reproduce this before even looking at
the patch :-)
- Arnaldo
> To avoid this, have __perf_session__process_events bail out early when
> the file has no data (i.e. it has no events).
>
> Signed-off-by: Mark Rutland <mark.rutl...@arm.com>
> Cc: Adrian Hunter <adrian.hun...@intel.com>
> Cc: Arnaldo Carvalho de Melo <a...@kernel.org>
> Cc: Ingo Molnar <mi...@redhat.com>
> Cc: Jiri Olsa <jo...@redhat.com>
> Cc: Peter Zijlstra <pet...@infradead.org>
> ---
> tools/perf/util/session.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
> index 8a4537e..fc3f7c9 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...");
> --
> 1.9.1
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