Hi Peter, On Mon, 11 Mar 2013 11:01:14 +0100, Peter Zijlstra wrote: > On Thu, 2013-03-07 at 13:19 +0900, Namhyung Kim wrote: >> From: Namhyung Kim <namhyung....@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 <hollm...@in.tum.de> >> Cc: Jiri Olsa <jo...@redhat.com> >> Cc: Vince Weaver <vi...@deater.net> >> Cc: Frederic Weisbecker <fweis...@gmail.com> >> Signed-off-by: Namhyung Kim <namhy...@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.
Hmm.. it seems that it needs whole perf_{remove_from,install_in}_context step to migrate them, right? Looks like not a simple job for me. :( Any advice? Thanks, Namhyung -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/