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SubjectRe: [PATCH] perf record: Fix continue profiling after draining the buffer
On Fri, Feb 05, 2021 at 07:35:22PM +0900, Namhyung Kim wrote:
> Hello,
>
> On Fri, Feb 5, 2021 at 3:50 PM Yang Jihong <yangjihong1@huawei.com> wrote:
> >
> > commit da231338ec9c098707c8a1e4d8a50e2400e2fe17 uses eventfd to solve rare race
> > where the setting and checking of 'done' which add done_fd to pollfd.
> > When draining buffer, revents of done_fd is 0 and evlist__filter_pollfd
> > function returns a non-zero value.
> > As a result, perf record does not stop profiling.
> >
> > The following simple scenarios can trigger this condition:
> >
> > sleep 10 &
> > perf record -p $!
> >
> > After the sleep process exits, perf record should stop profiling and exit.
> > However, perf record keeps running.
> >
> > If pollfd revents contains only POLLERR or POLLHUP,
> > perf record indicates that buffer is draining and need to stop profiling.
> > Use fdarray_flag__nonfilterable to set done eventfd to nonfilterable objects,
> > so that evlist__filter_pollfd does not filter and check done eventfd.
> >
> > Fixes: da231338ec9c (perf record: Use an eventfd to wakeup when done)
> > Signed-off-by: Yang Jihong <yangjihong1@huawei.com>
> > ---
> > tools/perf/builtin-record.c | 2 +-
> > tools/perf/util/evlist.c | 8 ++++++++
> > tools/perf/util/evlist.h | 4 ++++
> > 3 files changed, 13 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> > index fd3911650612..51e593e896ea 100644
> > --- a/tools/perf/builtin-record.c
> > +++ b/tools/perf/builtin-record.c
> > @@ -1663,7 +1663,7 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
> > status = -1;
> > goto out_delete_session;
> > }
> > - err = evlist__add_pollfd(rec->evlist, done_fd);
> > + err = evlist__add_wakeup_eventfd(rec->evlist, done_fd);
> > if (err < 0) {
> > pr_err("Failed to add wakeup eventfd to poll list\n");
> > status = err;
> > diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> > index 05363a7247c4..fea4c1e8010d 100644
> > --- a/tools/perf/util/evlist.c
> > +++ b/tools/perf/util/evlist.c
> > @@ -572,6 +572,14 @@ int evlist__filter_pollfd(struct evlist *evlist, short revents_and_mask)
> > return perf_evlist__filter_pollfd(&evlist->core, revents_and_mask);
> > }
> >
> > +#ifdef HAVE_EVENTFD_SUPPORT
> > +int evlist__add_wakeup_eventfd(struct evlist *evlist, int fd)
> > +{
> > + return perf_evlist__add_pollfd(&evlist->core, fd, NULL, POLLIN,
> > + fdarray_flag__nonfilterable);
> > +}
> > +#endif
>
> Does it build when HAVE_EVENTFD_SUPPORT is not defined?

yea, I was wondering the same.. but it's called only from
code within HAVE_EVENTFD_SUPPORT ifdef

jirka

>
> Thanks,
> Namhyung
>
>
> > +
> > int evlist__poll(struct evlist *evlist, int timeout)
> > {
> > return perf_evlist__poll(&evlist->core, timeout);
> > diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
> > index 1aae75895dea..6d4d62151bc8 100644
> > --- a/tools/perf/util/evlist.h
> > +++ b/tools/perf/util/evlist.h
> > @@ -142,6 +142,10 @@ struct evsel *evlist__find_tracepoint_by_name(struct evlist *evlist, const char
> > int evlist__add_pollfd(struct evlist *evlist, int fd);
> > int evlist__filter_pollfd(struct evlist *evlist, short revents_and_mask);
> >
> > +#ifdef HAVE_EVENTFD_SUPPORT
> > +int evlist__add_wakeup_eventfd(struct evlist *evlist, int fd);
> > +#endif
> > +
> > int evlist__poll(struct evlist *evlist, int timeout);
> >
> > struct evsel *evlist__id2evsel(struct evlist *evlist, u64 id);
> > --
> > 2.17.1
> >
>

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