Em Mon, Feb 22, 2021 at 09:31:51AM +0800, Yang Jihong escreveu:
> Hello,
>
> On 2021/2/19 1:09, Arnaldo Carvalho de Melo wrote:
> > Em Thu, Feb 18, 2021 at 10:20:53AM -0300, Arnaldo Carvalho de Melo escreveu:
> > > Em Fri, Feb 05, 2021 at 11:46:12AM +0100, Jiri Olsa escreveu:
> > > > 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 <yangjiho...@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 <yangjiho...@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
> > >
> > > Yes, this can't work on systems without eventfd, it will simply not
> > > build, and why do we have to make the definition of this function
> > > conditional on HAVE_EVENTFD_SUPPORT?
> > >
> > > I'm missing something :-\
> > >
> > > Yeah, this whole call to evlist__add_pollfd is already surrounded by
> > > #ifdef HAVE_EVENTFD_SUPPORT:
> > >
> > > 1656 if (zstd_init(&session->zstd_data, rec->opts.comp_level) <
> > > 0) {
> > > 1657 pr_err("Compression initialization failed.\n");
> > > 1658 return -1;
> > > 1659 }
> > > 1660 #ifdef HAVE_EVENTFD_SUPPORT
> > > 1661 done_fd = eventfd(0, EFD_NONBLOCK);
> > > 1662 if (done_fd < 0) {
> > > 1663 pr_err("Failed to create wakeup eventfd, error:
> > > %m\n");
> > > 1664 status = -1;
> > > 1665 goto out_delete_session;
> > > 1666 }
> > > 1667 err = evlist__add_pollfd(rec->evlist, done_fd);
> > > 1668 if (err < 0) {
> > > 1669 pr_err("Failed to add wakeup eventfd to poll
> > > list\n");
> > > 1670 status = err;
> > > 1671 goto out_delete_session;
> > > 1672 }
> > > 1673 #endif // HAVE_EVENTFD_SUPPORT
> > > 1674
> > > 1675 session->header.env.comp_type = PERF_COMP_ZSTD;
> > > 1676 session->header.env.comp_level = rec->opts.comp_level;
> > >
> > > Jiri, does your Acked-by stands? Namhyung?
> >
> > Thanks tested and applied, together with Jiri's Tested-by,
> >
> > - Arnaldo
> > .
> >
> Is this patch okay? Is there anything that needs to be modified?
It was merged:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/tools/perf/builtin-record.c?id=e16c2ce7c5ed5de881066c1fd10ba5c09af69559
- Arnaldo
