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([216.195.201.23]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-36ca38d46fcsm9019567eec.13.2026.11.04.08.58.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Nov 2026 08:58:23 -0800 (PST) From: Kunwu Chan To: paulmck@kernel.org, boqun@kernel.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, corbet@lwn.net, mingo@redhat.com, frederic@kernel.org, neeraj.upadhyay@kernel.org, josh@joshtriplett.org, urezki@gmail.com, dave@stgolabs.net Cc: stern@rowland.harvard.edu, parri.andrea@gmail.com, will@kernel.org, dhowells@redhat.com, j.alglave@ucl.ac.uk, luc.maranget@inria.fr, akiyks@gmail.com, dlustig@nvidia.com, joelagnelf@nvidia.com, skhan@linuxfoundation.org, rdunlap@infradead.org, longman@redhat.com, rostedt@goodmis.org, qiang.zhang@linux.dev, kunwu.chan@gmail.com, brads@mainlining.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, lkmm@lists.linux.dev, linux-doc@vger.kernel.org, rcu@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH 20/28] locking/lockdep: Use hazptr to wait for dynamic key lookups Date: Thu, 5 Nov 2026 00:54:38 +0800 Message-ID: <20261104165504.2430480-21-kunwu.chan@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20261104165504.2430480-1-kunwu.chan@gmail.com> References: <20261104165504.2430480-1-kunwu.chan@gmail.com> X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Replace the system-wide synchronize_rcu_expedited() in lockdep_unregister_key() with a hazptr_synchronize() scoped to the per-key hash bucket. Suggested-by: Boqun Feng Signed-off-by: Kunwu Chan --- kernel/locking/lockdep.c | 25 +++++++++++++++---------- 1 file changed, 15 insertions(+), 10 deletions(-) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index c3dc84a7cef2..256f23a9041d 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -58,6 +58,7 @@ #include #include #include +#include #include @@ -1308,14 +1309,19 @@ static bool is_dynamic_key(const struct lock_class_key *key) hash_head = keyhashentry(key); - rcu_read_lock(); - hlist_for_each_entry_rcu(k, hash_head, hash_entry) { - if (k == key) { - found = true; - break; + { + struct hazptr_ctx ctx; + void *bucket = hash_head; + + scoped_guard(hazptr, &ctx, &bucket) { + hlist_for_each_entry_rcu(k, hash_head, hash_entry, 1) { + if (k == key) { + found = true; + break; + } + } } } - rcu_read_unlock(); return found; } @@ -6717,11 +6723,10 @@ void lockdep_unregister_key(struct lock_class_key *key) * * Some operations like __qdisc_destroy() will call this in a debug * kernel, and the network traffic is disabled while waiting, hence - * the delay of the wait matters in debugging cases. Currently use a - * synchronize_rcu_expedited() to speed up the wait at the cost of - * system IPIs. TODO: Replace RCU with hazptr for this. + * the delay of the wait matters in debugging cases. Replace the + * expedited RCU wait with hazptr_synchronize(). */ - synchronize_rcu_expedited(); + hazptr_synchronize(keyhashentry(key)); } EXPORT_SYMBOL_GPL(lockdep_unregister_key); -- 2.43.0