Messages in this thread | | | Subject | Re: [PATCH] perf record: Fix continue profiling after draining the buffer | From | Yang Jihong <> | Date | Thu, 18 Feb 2021 18:18:46 +0800 |
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Hello,
On 2021/2/7 8:56, Yang Jihong wrote: > Hello, > > On 2021/2/5 18:46, Jiri Olsa wrote: >> 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 >>> >>> > I have tested that if "eventfd" feature is removed from the > FEATURE_TESTS_BASIC list in Makefile.feature, > evlist__add_wakeup_eventfd will not be build. > > Modify as follows: > > diff --git a/tools/build/Makefile.feature b/tools/build/Makefile.feature > index 97cbfb31b762..d1603050764a 100644 > --- a/tools/build/Makefile.feature > +++ b/tools/build/Makefile.feature > @@ -32,7 +32,6 @@ FEATURE_TESTS_BASIC := \ > backtrace \ > dwarf \ > dwarf_getlocations \ > - eventfd \ > fortify-source \ > sync-compare-and-swap \ > get_current_dir_name \ > > Thanks, > Yang > >>>> + >>>> 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 >>>> >>> >> >> . >> Do have any other questions about this patch? Look forward to your review.
Thanks, Yang
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