perf: Re-instate the linear PMU search

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 cleanup.

Reported-by: Nathan Chancellor <nathan@kernel.org>
Reported-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20230605101401.GL38236@hirez.programming.kicks-ass.net

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 231b187..c01bbe9 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -11630,27 +11630,38 @@ static struct pmu *perf_init_event(struct perf_event *event)
        }
 
 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;
 
-       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;
+               }
 
-       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;
        }
 
-fail:
-       if (ret)
-               pmu = ERR_PTR(ret);
+       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:
+       pmu = ERR_PTR(-ENOENT);
 unlock:
        srcu_read_unlock(&pmus_srcu, idx);