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linux-modules@vger.kernel.org, rcu@vger.kernel.org, linux-nfs@vger.kernel.org, linux-rt-devel@lists.linux.dev Subject: [PATCH v17 29/47] cpu/hotplug: use a weaker annotation in AP thread Date: Thu, 2 Oct 2025 17:12:29 +0900 Message-Id: <20251002081247.51255-30-byungchul@sk.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20251002081247.51255-1-byungchul@sk.com> References: <20251002081247.51255-1-byungchul@sk.com> X-Brightmail-Tracker: H4sIAAAAAAAAAzXSe0hTcRQH8H73PWlym4G3WVQLCaTMzOJADwqpLlZQ+Ef0drVLG02N+SiN Qi1Lq5VZ00qy+ciGW2VbD7W0MlrZEl0vV21TS1NJk6SZr2Fb0n8fvt/DOf8cBpe8J6WMKiFZ 0CTI1TIqgAjon1qyMCjKrYwYsc2DNk8Ogj9jRTh48600/B75QoPpXiYGuo5OCgp7MwkYqDiL oPfFeuhve0TChKsbg9ahPgSdT08h8BYcgOulFgrGmppxKNS1IOip8uX3rG4EdYYsCrry7uPw rjMQ3nsGKGjUnaHgZxUF+qw6Eo6X3aGg4JqZgJr2WhrsP8YxcBbkY2A0b/Id93V3g6GosAeD N2VOAioyQmFCnwhWYzcNrvM6Am73N5PQ6P5IQtvLkyQ8zGinwfzpBYKcWg8B5m++ouRkOQFX ip0UPK5rJCDH+xuBtforBmer7pPgNk2QcKfbgYHN+oqA5tpbJNxotWPQ0e4gwdL0BoehcyHQ 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Q7ZA2IQ7GgcRqH8OmAJbYQNn3X52dXRBQl0erQxxQ9rxIWGI= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: cb92173d1f0 ("locking/lockdep, cpu/hotplug: Annotate AP thread") was introduced to make lockdep_assert_cpus_held() work in AP thread. However, the annotation is too strong for that purpose. We don't have to use more than try lock annotation for that. rwsem_acquire() implies: 1. might be a waiter on contention of the lock. 2. enter to the critical section of the lock. All we need in here is to act 2, not 1. So trylock version of annotation is sufficient for that purpose. Now that dept partially relies on lockdep annotaions, dept interpets rwsem_acquire() as a potential wait and might report a deadlock by the wait. Replace it with trylock version of annotation. Signed-off-by: Byungchul Park --- kernel/cpu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/cpu.c b/kernel/cpu.c index db9f6c539b28..285d7fa55523 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -538,7 +538,7 @@ int lockdep_is_cpus_held(void) static void lockdep_acquire_cpus_lock(void) { - rwsem_acquire(&cpu_hotplug_lock.dep_map, 0, 0, _THIS_IP_); + rwsem_acquire(&cpu_hotplug_lock.dep_map, 0, 1, _THIS_IP_); } static void lockdep_release_cpus_lock(void) -- 2.17.1