From 657ee5531903339b06697581532ed32d4762526e Mon Sep 17 00:00:00 2001 From: Song Liu Date: Mon, 11 Mar 2019 22:30:50 -0700 Subject: perf evlist: Introduce side band thread This patch introduces side band thread that captures extended information for events like PERF_RECORD_BPF_EVENT. This new thread uses its own evlist that uses ring buffer with very low watermark for lower latency. To use side band thread, we need to: 1. add side band event(s) by calling perf_evlist__add_sb_event(); 2. calls perf_evlist__start_sb_thread(); 3. at the end of perf run, perf_evlist__stop_sb_thread(). In the next patch, we use this thread to handle PERF_RECORD_BPF_EVENT. Committer notes: Add fix by Jiri Olsa for when te sb_tread can't get started and then at the end the stop_sb_thread() segfaults when joining the (non-existing) thread. That can happen when running 'perf top' or 'perf record' as a normal user, for instance. Further checks need to be done on top of this to more graciously handle these possible failure scenarios. Signed-off-by: Song Liu Reviewed-by: Jiri Olsa Tested-by: Arnaldo Carvalho de Melo Cc: Alexei Starovoitov Cc: Daniel Borkmann Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Stanislav Fomichev Link: http://lkml.kernel.org/r/20190312053051.2690567-15-songliubraving@fb.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/builtin-record.c | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'tools/perf/builtin-record.c') diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c index e79faccd7842..6f645fd72fed 100644 --- a/tools/perf/builtin-record.c +++ b/tools/perf/builtin-record.c @@ -1137,6 +1137,7 @@ static int __cmd_record(struct record *rec, int argc, const char **argv) struct perf_data *data = &rec->data; struct perf_session *session; bool disabled = false, draining = false; + struct perf_evlist *sb_evlist = NULL; int fd; atexit(record__sig_exit); @@ -1237,6 +1238,11 @@ static int __cmd_record(struct record *rec, int argc, const char **argv) goto out_child; } + if (perf_evlist__start_sb_thread(sb_evlist, &rec->opts.target)) { + pr_debug("Couldn't start the BPF side band thread:\nBPF programs starting from now on won't be annotatable\n"); + opts->no_bpf_event = true; + } + err = record__synthesize(rec, false); if (err < 0) goto out_child; @@ -1487,6 +1493,9 @@ out_child: out_delete_session: perf_session__delete(session); + + if (!opts->no_bpf_event) + perf_evlist__stop_sb_thread(sb_evlist); return status; } -- cgit v1.2.3