On Mon, Jun 05, 2023 at 12:14:01PM +0200, Peter Zijlstra wrote:
> On Mon, Jun 05, 2023 at 11:27:31AM +0200, Peter Zijlstra wrote:
>
> > That said; given that this commit has been tagged twice now, I suppose I
> > should go revert it and we'll try again after a more thorough audit.
>
> I'll go queue this then...
>
> ---
> Subject: perf: Re-instate the linear PMU search
> From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Date: Mon Jun 5 11:42:39 CEST 2023
>
> Full revert of commit 9551fbb64d09 ("perf/core: Remove pmu linear
> searching code").
>
> Some architectures (notably arm/arm64) still relied on the linear
> search in order to find the PMU that consumes
> PERF_TYPE_{HARDWARE,HW_CACHE,RAW}.
>
> This will need a more thorought audit and clean.
>
> Reported-by: Nathan Chancellor <nathan@xxxxxxxxxx>
> Reported-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Acked-by: Mark Rutland <mark.rutland@xxxxxxx>
Thanks for sorting this out!
Mark.
> ---
> kernel/events/core.c | 39 +++++++++++++++++++++++++--------------
> 1 file changed, 25 insertions(+), 14 deletions(-)
>
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -11630,27 +11630,38 @@ static struct pmu *perf_init_event(struc
> }
>
> again:
> - ret = -ENOENT;
> rcu_read_lock();
> pmu = idr_find(&pmu_idr, type);
> rcu_read_unlock();
> - if (!pmu)
> - goto fail;
> + if (pmu) {
> + if (event->attr.type != type && type != PERF_TYPE_RAW &&
> + !(pmu->capabilities & PERF_PMU_CAP_EXTENDED_HW_TYPE))
> + goto fail;
> +
> + ret = perf_try_init_event(pmu, event);
> + if (ret == -ENOENT && event->attr.type != type && !extended_type) {
> + type = event->attr.type;
> + goto again;
> + }
>
> - if (event->attr.type != type && type != PERF_TYPE_RAW &&
> - !(pmu->capabilities & PERF_PMU_CAP_EXTENDED_HW_TYPE))
> - goto fail;
> -
> - ret = perf_try_init_event(pmu, event);
> - if (ret == -ENOENT && event->attr.type != type && !extended_type) {
> - type = event->attr.type;
> - goto again;
> + if (ret)
> + pmu = ERR_PTR(ret);
> +
> + goto unlock;
> }
>
> + list_for_each_entry_rcu(pmu, &pmus, entry, lockdep_is_held(&pmus_srcu)) {
> + ret = perf_try_init_event(pmu, event);
> + if (!ret)
> + goto unlock;
> +
> + if (ret != -ENOENT) {
> + pmu = ERR_PTR(ret);
> + goto unlock;
> + }
> + }
> fail:
> - if (ret)
> - pmu = ERR_PTR(ret);
> -
> + pmu = ERR_PTR(-ENOENT);
> unlock:
> srcu_read_unlock(&pmus_srcu, idx);
>
