On Tue, Aug 26, 2025 at 12:15:23PM +0100, Mark Rutland wrote: > On Wed, Aug 13, 2025 at 06:00:54PM +0100, Robin Murphy wrote: > > The group validation logic shared by the HiSilicon HNS3/PCIe drivers is > > a bit off, in that given a software group leader, it will consider that > > event *in place of* the actual new event being opened. At worst this > > could theoretically allow an unschedulable group if the software event > > config happens to look like one of the hardware siblings. > > > > The uncore framework avoids that particular issue, > > What is "the uncore framework"? I'm not sure exactly what you're > referring to, nor how that composes with the problem described above. > > > but all 3 also share the common issue of not preventing racy access to > > the sibling list, > > Can you please elaborate on this racy access to the silbing list? I'm > not sure exactly what you're referring to.
Ah, I think you're referring to the issue in: https://lore.kernel.org/linux-arm-kernel/Zg0l642PgQ7T3a8Z@FVFF77S0Q05N/ ... where when creatign a new event which is its own group leader, lockdep_assert_event_ctx(event) fires in for_each_sibling_event(), because the new event's context isn't locked... > > diff --git a/drivers/perf/hisilicon/hisi_uncore_pmu.c > > b/drivers/perf/hisilicon/hisi_uncore_pmu.c > > index a449651f79c9..3c531b36cf25 100644 > > --- a/drivers/perf/hisilicon/hisi_uncore_pmu.c > > +++ b/drivers/perf/hisilicon/hisi_uncore_pmu.c > > @@ -101,26 +101,17 @@ static bool hisi_validate_event_group(struct > > perf_event *event) > > /* Include count for the event */ > > int counters = 1; > > > > - if (!is_software_event(leader)) { > > - /* > > - * We must NOT create groups containing mixed PMUs, although > > - * software events are acceptable > > - */ > > - if (leader->pmu != event->pmu) > > - return false; > > + if (leader == event) > > + return true; ... and hence bailing out here avoids that? It's not strictly "racy access to the sibling list", becuase there's nothing else accessing the list; it's just that this is the simplest way to appease lockdep while avoiding false negatives. It'd probably be better to say something like "the common issue of calling for_each_sibling_event() when initialising a new group leader", and maybe to spell that out a bit. Mark.
