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>
---
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);
