[PATCH v7 0/3] perf/core: sched_task() dispatch and branch entry fixes

[Andrii Nakryiko]

On Tue, Sep 15, 2026 at 3:47 PM Ian Rogers <irogers at google.com> wrote:
>
> On Thu, Sep 3, 2026 at 7:45 PM wuyifan <wuyifan50 at huawei.com> wrote:
> >
> > Hi Puranjay,
> >
> > On 8/10/2026 9:35 PM, Puranjay Mohan wrote:
> > > These three fixes were found while adding BRBE support for
> > > bpf_get_branch_snapshot() on arm64 and were carried in that series until
> > > v6 [1]. They do not depend on it, so they go on their own; the version
> > > number continues from that series to avoid two numbering schemes for the
> > > same patches.
> > perf record -C <cpu> -b [<command>] triggers a NULL pointer dereference
> > in armv8pmu_sched_task().
> >
> > Commit fa9d27773873 ("perf: arm_pmu: Kill last use of per-CPU cpu_armpmu
> > pointer") changed armv8pmu_sched_task() from reading the per-CPU
> > cpu_armpmu variable to dereferencing pmu_ctx->pmu via
> > to_arm_pmu(pmu_ctx->pmu). Meanwhile, commit bd2756811766 ("perf:
> > Rewrite core context handling") made __perf_pmu_sched_task() pass
> > cpc->task_epc to pmu->sched_task(). cpc->task_epc is only non-NULL
> > while a task context is scheduled in; CPU-bound events do not schedule a
> > task context, so cpc->task_epc stays NULL. The NULL argument is dereferenced
> > and crashes.
> >
> > With the patches applied, perf record -C <cpu> -b no longer crashes,
> > and system-wide perf record -b -e <event> -a alongside a task-bound event
> > on a different CPU runs without any WARN_ON.
> >
> > Tested-by: Yifan Wu <wuyifan50 at huawei.com>
>
> Hi,
>
> Is there anything that needs doing to land this series? Avoiding a
> perf crash seems worthwhile. I believe Peter and Ingo are best placed
> to review the changes to kernel/events/core.c.
>

another ping... seems like worthwhile problems to fix

> Thanks,
> Ian
>