Hi Jiri,
On Mon, Dec 12, 2016 at 11:35:42AM +0100, Jiri Olsa wrote:
> Adding perf_evsel::ignore_missing_cpu_thread bool.
>
> When set true, it allows perf to ignore error of missing
> pid of perf event syscall.
>
> We remove missing thread id from the thread_map, so the
> rest of the processing like ioctl and mmap won't get
> disturbed with -1 fd.
>
> The reason for supporting this is to ease up monitoring
> group of pids, that 'disappear' before perf opens their
> event. This currently leads perf to report error and exit
> and makes perf record's -u option unusable under certain
> setup.
>
> With this change we will allow this race and ignore such
> failure with following warning:
>
> WARNING: Ignored open failure for pid 8605
>
> Signed-off-by: Jiri Olsa <jo...@kernel.org>
> Cc: David Ahern <dsah...@gmail.com>
> Cc: Namhyung Kim <namhy...@kernel.org>
> Cc: Peter Zijlstra <a.p.zijls...@chello.nl>
> Link: http://lkml.kernel.org/n/tip-atmzsjyhrt1j6xjwwmb84...@git.kernel.org
> ---
> tools/perf/perf.h | 1 +
> tools/perf/util/evsel.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
> tools/perf/util/evsel.h | 1 +
> 3 files changed, 46 insertions(+)
>
> diff --git a/tools/perf/perf.h b/tools/perf/perf.h
> index 9a0236a4cf95..1c27d947c2fe 100644
> --- a/tools/perf/perf.h
> +++ b/tools/perf/perf.h
> @@ -55,6 +55,7 @@ struct record_opts {
> bool all_user;
> bool tail_synthesize;
> bool overwrite;
> + bool ignore_missing_thread;
> unsigned int freq;
> unsigned int mmap_pages;
> unsigned int auxtrace_mmap_pages;
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index fd61ebd77c26..ac87f1637ae9 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -990,6 +990,8 @@ void perf_evsel__config(struct perf_evsel *evsel, struct
> record_opts *opts,
> * it overloads any global configuration.
> */
> apply_config_terms(evsel, opts);
> +
> + evsel->ignore_missing_thread = opts->ignore_missing_thread;
> }
>
> static int perf_evsel__alloc_fd(struct perf_evsel *evsel, int ncpus, int
> nthreads)
> @@ -1419,6 +1421,33 @@ static int __open_attr__fprintf(FILE *fp, const char
> *name, const char *val,
> return fprintf(fp, " %-32s %s\n", name, val);
> }
>
> +static bool ignore_missing_thread(struct perf_evsel *evsel,
> + struct thread_map *threads,
> + int thread, int err)
> +{
> + if (!evsel->ignore_missing_thread)
> + return false;
> +
> + /* The system wide setup does not work with threads. */
> + if (!evsel->system_wide)
> + return false;
I'm bit confused with this. Shouldn't the condition be positive?
Thanks,
Namhyung
> +
> + /* The -ESRCH is perf event syscall errno for pid's not found. */
> + if (err != -ESRCH)
> + return false;
> +
> + /* If there's only one thread, let it fail. */
> + if (threads->nr == 1)
> + return false;
> +
> + if (thread_map__remove(threads, thread))
> + return false;
> +
> + pr_warning("WARNING: Ignored open failure for pid %d\n",
> + thread_map__pid(threads, thread));
> + return true;
> +}
> +
> static int __perf_evsel__open(struct perf_evsel *evsel, struct cpu_map *cpus,
> struct thread_map *threads)
> {
> @@ -1491,6 +1520,21 @@ static int __perf_evsel__open(struct perf_evsel
> *evsel, struct cpu_map *cpus,
>
> if (fd < 0) {
> err = -errno;
> +
> + if (ignore_missing_thread(evsel, threads,
> thread, err)) {
> + /*
> + * We just removed 1 thread, so take a
> step
> + * back on thread index and lower the
> upper
> + * nthreads limit.
> + */
> + nthreads--;
> + thread--;
> +
> + /* ... and pretend like nothing have
> happened. */
> + err = 0;
> + continue;
> + }
> +
> pr_debug2("\nsys_perf_event_open failed, error
> %d\n",
> err);
> goto try_fallback;
> diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
> index 6abb89cd27f9..06ef6f29efa1 100644
> --- a/tools/perf/util/evsel.h
> +++ b/tools/perf/util/evsel.h
> @@ -120,6 +120,7 @@ struct perf_evsel {
> bool tracking;
> bool per_pkg;
> bool precise_max;
> + bool ignore_missing_thread;
> /* parse modifier helper */
> int exclude_GH;
> int nr_members;
> --
> 2.7.4
>
