Messages in this thread | | | Subject | Re: [PATCH] perf record: Fix continue profiling after draining the buffer | From | Yang Jihong <> | Date | Thu, 4 Mar 2021 09:19:32 +0800 |
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On 2021/3/4 0:43, Arnaldo Carvalho de Melo wrote: > 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 <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 >>>> >>>> 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 > . > Thanks. Yang
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