Messages in this thread | | | Subject | Re: [PATCH 2/2] perf: Fix mixed hw/sw event group initialization | From | Peter Zijlstra <> | Date | Mon, 11 Mar 2013 11:01:14 +0100 |
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On Thu, 2013-03-07 at 13:19 +0900, Namhyung Kim wrote: > From: Namhyung Kim <namhyung.kim@lge.com> > > There's a problem with mixed hw/sw group when the leader is a software > event. For instance:
> Jiri's patch 0231bb533675 ("perf: Fix event group context move") fixed > a part of problem but there's a devil still.. > > The problem arose when a sw event is added to already moved (to hw > context) group whose leader also is a sw event. In the above example > > 1. task-clock (sw event) is a group leader (has PERF_GROUP_SOFTWARE) > 2. cycles (hw event) is added, so the leader moved to the hw context > 3. faults (sw event) is added but the leader also is a sw event > 4. after find_get_context(), ctx is not same as leader->ctx since the > leader had moved to the hw context (-EINVAL) > > Fix it by adding new PERF_GROUP_MIXED flag and use leader's ctx->pmu > if it's set.
> Reported-by: Andreas Hollmann <hollmann@in.tum.de> > Cc: Jiri Olsa <jolsa@redhat.com> > Cc: Vince Weaver <vince@deater.net> > Cc: Frederic Weisbecker <fweisbec@gmail.com> > Signed-off-by: Namhyung Kim <namhyung@kernel.org> > --- > include/linux/perf_event.h | 1 + > kernel/events/core.c | 37 ++++++++++++++++++++++--------------- > 2 files changed, 23 insertions(+), 15 deletions(-) > > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h > index e47ee462c2f2..001a3b64fe61 100644 > --- a/include/linux/perf_event.h > +++ b/include/linux/perf_event.h > @@ -285,6 +285,7 @@ typedef void (*perf_overflow_handler_t)(struct perf_event *, > > enum perf_group_flag { > PERF_GROUP_SOFTWARE = 0x1, > + PERF_GROUP_MIXED = 0x2, > }; > > #define SWEVENT_HLIST_BITS 8 > diff --git a/kernel/events/core.c b/kernel/events/core.c > index 007dfe846d4d..06266d5ed500 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -6441,6 +6441,8 @@ out: > * @pid: target pid > * @cpu: target cpu > * @group_fd: group leader event fd > + * @flags: flags which controls the meaning of arguments. > + * see PERF_FLAG_* > */ > SYSCALL_DEFINE5(perf_event_open, > struct perf_event_attr __user *, attr_uptr, > @@ -6536,26 +6538,30 @@ SYSCALL_DEFINE5(perf_event_open, > */ > pmu = event->pmu; > > - if (group_leader && > - (is_software_event(event) != is_software_event(group_leader))) { > - if (is_software_event(event)) { > - /* > - * If event and group_leader are not both a software > - * event, and event is, then group leader is not. > - * > - * Allow the addition of software events to !software > - * groups, this is safe because software events never > - * fail to schedule. > - */ > - pmu = group_leader->pmu; > - } else if (is_software_event(group_leader) && > - (group_leader->group_flags & PERF_GROUP_SOFTWARE)) { > + if (group_leader) { > + if (group_leader->group_flags & PERF_GROUP_SOFTWARE) { > /* > * In case the group is a pure software group, and we > * try to add a hardware event, move the whole group to > * the hardware context. > */ > - move_group = 1; > + if (!is_software_event(event)) > + move_group = 1; > + } else if (group_leader->group_flags & PERF_GROUP_MIXED) { > + /* > + * The group leader was moved on to a hardware context, > + * so move this event also. > + */ > + if (is_software_event(event)) > + pmu = group_leader->ctx->pmu; > + } else if (!is_software_event(group_leader)) { > + /* > + * Allow the addition of software events to !software > + * groups, this is safe because software events never > + * fail to schedule. > + */ > + if (is_software_event(event)) > + pmu = group_leader->pmu; > } > } > > @@ -6650,6 +6656,7 @@ SYSCALL_DEFINE5(perf_event_open, > perf_install_in_context(ctx, sibling, event->cpu); > get_ctx(ctx); > } > + group_leader->group_flags = PERF_GROUP_MIXED; > } > > perf_install_in_context(ctx, event, event->cpu);
This seems reasonable, but I think the perf_group_detach thing needs to migrate events between pmu's as well to complete the whole mess.
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