linux-kernel - [PATCH] perf/core: remove a meaningless pair of rcu_read

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Date:   Wed,  8 Jun 2022 17:09:38 +0800
From:   Yanfei Xu <yanfei.xu@...el.com>
To:     peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
        mark.rutland@....com, alexander.shishkin@...ux.intel.com,
        jolsa@...nel.org, namhyung@...nel.org
Cc:     linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org
Subject: [PATCH] perf/core: remove a meaningless pair of rcu_read_{,un}lock()

Per the codes, this pair of rcu_read_{,un}lock() protects nothing.
Let's remove it.

Further, the variable "pmu" is safe as it is in the SRCU read-side
critical scope of "pmus_srcu" and perf_pmu_unregister() delete it
after calling synchronize_srcu.

Signed-off-by: Yanfei Xu <yanfei.xu@...el.com>
---
 kernel/events/core.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 950b25c3f210..36b0df6feab4 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -11296,9 +11296,7 @@ static struct pmu *perf_init_event(struct perf_event *event)
 	}
 
 again:
-	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))
-- 
2.32.0