linux-kernel - Re: [PATCH v3 2/3] perf/ibs: Fix interface via core pmu events

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Message-ID: <20230502153701.GF1597538@hirez.programming.kicks-ass.net>
Date:   Tue, 2 May 2023 17:37:01 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Ravi Bangoria <ravi.bangoria@....com>
Cc:     namhyung@...nel.org, eranian@...gle.com, acme@...nel.org,
        mark.rutland@....com, jolsa@...nel.org, irogers@...gle.com,
        bp@...en8.de, kan.liang@...ux.intel.com, adrian.hunter@...el.com,
        maddy@...ux.ibm.com, x86@...nel.org,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        sandipan.das@....com, ananth.narayan@....com,
        santosh.shukla@....com
Subject: Re: [PATCH v3 2/3] perf/ibs: Fix interface via core pmu events

On Tue, Apr 25, 2023 at 07:52:04PM +0530, Ravi Bangoria wrote:
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 151299940d9a..232121a6d1e2 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -11648,16 +11648,6 @@ static struct pmu *perf_init_event(struct perf_event *event)
>  		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:
>  	pmu = ERR_PTR(-ENOENT);
>  unlock:

Would it make sense to put the above and the below cleanup in a separate
patch after this?

--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -11631,25 +11631,24 @@ static struct pmu *perf_init_event(struc
 	rcu_read_lock();
 	pmu = idr_find(&pmu_idr, type);
 	rcu_read_unlock();
-	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 (!pmu)
+		goto unlock;
 
-		if (ret)
-			pmu = ERR_PTR(ret);
+	ret = -ENOENT;
+	if (event->attr.type != type && type != PERF_TYPE_RAW &&
+	    !(pmu->capabilities & PERF_PMU_CAP_EXTENDED_HW_TYPE))
+		goto fail;
 
-		goto unlock;
+	ret = perf_try_init_event(pmu, event);
+	if (ret == -ENOENT && event->attr.type != type && !extended_type) {
+		type = event->attr.type;
+		goto again;
 	}
 
 fail:
-	pmu = ERR_PTR(-ENOENT);
+	if (ret)
+		pmu = ERR_PTR(ret);
+
 unlock:
 	srcu_read_unlock(&pmus_srcu, idx);