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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id n20sm12483453qkn.118.2019.11.05.21.30.05 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 05 Nov 2019 21:30:05 -0800 (PST) From: Qian Cai To: mingo@redhat.com, peterz@infradead.org Cc: andi@firstfloor.org, acme@kernel.org, mark.rutland@arm.com, jolsa@redhat.com, namhyung@kernel.org, linux-kernel@vger.kernel.org, Qian Cai Subject: [PATCH -next] perf/core: fix unlock balance in perf_init_event Date: Wed, 6 Nov 2019 00:29:35 -0500 Message-Id: <20191106052935.8352-1-cai@lca.pw> X-Mailer: git-send-email 2.21.0 (Apple Git-122) MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The -next commit "perf/core: Optimize perf_init_event()" [1] introduced an unlock imbalance in perf_init_event() where it calls "goto again" and then only repeat rcu_read_unlock(). WARNING: bad unlock balance detected! perf_event_open/6185 is trying to release lock (rcu_read_lock) at: [] perf_event_alloc+0xbb9/0x17f0 but there are no more locks to release! other info that might help us debug this: 2 locks held by perf_event_open/6185: #0: ffff888526780b50 (&sig->cred_guard_mutex){+.+.}, at: __do_sys_perf_event_open+0x6ee/0x1460 #1: ffffffffb866b4e8 (&pmus_srcu){....}, at: perf_event_alloc+0xab8/0x17f0 Call Trace: dump_stack+0xa0/0xea print_unlock_imbalance_bug.cold.40+0xb1/0xb6 lock_release+0x349/0x4b0 perf_event_alloc+0xbcf/0x17f0 __do_sys_perf_event_open+0x1e2/0x1460 __x64_sys_perf_event_open+0x62/0x70 do_syscall_64+0xcc/0xaec entry_SYSCALL_64_after_hwframe+0x49/0xbe [1] https://lore.kernel.org/lkml/20191022092307.425783389@infradead.org/ Signed-off-by: Qian Cai --- kernel/events/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index cfd89b4a02d8..8226d6ecdb86 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -10307,7 +10307,6 @@ static struct pmu *perf_init_event(struct perf_event *event) goto unlock; } - rcu_read_lock(); /* * PERF_TYPE_HARDWARE and PERF_TYPE_HW_CACHE * are often aliases for PERF_TYPE_RAW. @@ -10317,6 +10316,7 @@ static struct pmu *perf_init_event(struct perf_event *event) type = PERF_TYPE_RAW; again: + rcu_read_lock(); pmu = idr_find(&pmu_idr, type); rcu_read_unlock(); if (pmu) { -- 2.21.0 (Apple Git-122)