From c82f898d873ce10d88f8d60b38c8dd19f1ed7c66 Mon Sep 17 00:00:00 2001 From: Dmitry Osipenko Date: Tue, 10 May 2022 02:32:10 +0300 Subject: [PATCH] notifier: Add blocking/atomic_notifier_chain_register_unique_prio() MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Add variant of blocking/atomic_notifier_chain_register() functions that allow registration of a notifier only if it has unique priority, otherwise -EBUSY error code is returned by the new functions. Reviewed-by: Michał Mirosław Signed-off-by: Dmitry Osipenko Signed-off-by: Rafael J. Wysocki --- include/linux/notifier.h | 5 +++ kernel/notifier.c | 88 +++++++++++++++++++++++++++++++++++++----------- 2 files changed, 74 insertions(+), 19 deletions(-) diff --git a/include/linux/notifier.h b/include/linux/notifier.h index 95e2440..aef88c2 100644 --- a/include/linux/notifier.h +++ b/include/linux/notifier.h @@ -150,6 +150,11 @@ extern int raw_notifier_chain_register(struct raw_notifier_head *nh, extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh, struct notifier_block *nb); +extern int atomic_notifier_chain_register_unique_prio( + struct atomic_notifier_head *nh, struct notifier_block *nb); +extern int blocking_notifier_chain_register_unique_prio( + struct blocking_notifier_head *nh, struct notifier_block *nb); + extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh, struct notifier_block *nb); extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh, diff --git a/kernel/notifier.c b/kernel/notifier.c index 137b902..0d5bd62 100644 --- a/kernel/notifier.c +++ b/kernel/notifier.c @@ -20,7 +20,8 @@ BLOCKING_NOTIFIER_HEAD(reboot_notifier_list); */ static int notifier_chain_register(struct notifier_block **nl, - struct notifier_block *n) + struct notifier_block *n, + bool unique_priority) { while ((*nl) != NULL) { if (unlikely((*nl) == n)) { @@ -30,6 +31,8 @@ static int notifier_chain_register(struct notifier_block **nl, } if (n->priority > (*nl)->priority) break; + if (n->priority == (*nl)->priority && unique_priority) + return -EBUSY; nl = &((*nl)->next); } n->next = *nl; @@ -144,13 +147,36 @@ int atomic_notifier_chain_register(struct atomic_notifier_head *nh, int ret; spin_lock_irqsave(&nh->lock, flags); - ret = notifier_chain_register(&nh->head, n); + ret = notifier_chain_register(&nh->head, n, false); spin_unlock_irqrestore(&nh->lock, flags); return ret; } EXPORT_SYMBOL_GPL(atomic_notifier_chain_register); /** + * atomic_notifier_chain_register_unique_prio - Add notifier to an atomic notifier chain + * @nh: Pointer to head of the atomic notifier chain + * @n: New entry in notifier chain + * + * Adds a notifier to an atomic notifier chain if there is no other + * notifier registered using the same priority. + * + * Returns 0 on success, %-EEXIST or %-EBUSY on error. + */ +int atomic_notifier_chain_register_unique_prio(struct atomic_notifier_head *nh, + struct notifier_block *n) +{ + unsigned long flags; + int ret; + + spin_lock_irqsave(&nh->lock, flags); + ret = notifier_chain_register(&nh->head, n, true); + spin_unlock_irqrestore(&nh->lock, flags); + return ret; +} +EXPORT_SYMBOL_GPL(atomic_notifier_chain_register_unique_prio); + +/** * atomic_notifier_chain_unregister - Remove notifier from an atomic notifier chain * @nh: Pointer to head of the atomic notifier chain * @n: Entry to remove from notifier chain @@ -222,18 +248,9 @@ bool atomic_notifier_call_chain_is_empty(struct atomic_notifier_head *nh) * synchronized by an rwsem. */ -/** - * blocking_notifier_chain_register - Add notifier to a blocking notifier chain - * @nh: Pointer to head of the blocking notifier chain - * @n: New entry in notifier chain - * - * Adds a notifier to a blocking notifier chain. - * Must be called in process context. - * - * Returns 0 on success, %-EEXIST on error. - */ -int blocking_notifier_chain_register(struct blocking_notifier_head *nh, - struct notifier_block *n) +static int __blocking_notifier_chain_register(struct blocking_notifier_head *nh, + struct notifier_block *n, + bool unique_priority) { int ret; @@ -243,16 +260,49 @@ int blocking_notifier_chain_register(struct blocking_notifier_head *nh, * such times we must not call down_write(). */ if (unlikely(system_state == SYSTEM_BOOTING)) - return notifier_chain_register(&nh->head, n); + return notifier_chain_register(&nh->head, n, unique_priority); down_write(&nh->rwsem); - ret = notifier_chain_register(&nh->head, n); + ret = notifier_chain_register(&nh->head, n, unique_priority); up_write(&nh->rwsem); return ret; } + +/** + * blocking_notifier_chain_register - Add notifier to a blocking notifier chain + * @nh: Pointer to head of the blocking notifier chain + * @n: New entry in notifier chain + * + * Adds a notifier to a blocking notifier chain. + * Must be called in process context. + * + * Returns 0 on success, %-EEXIST on error. + */ +int blocking_notifier_chain_register(struct blocking_notifier_head *nh, + struct notifier_block *n) +{ + return __blocking_notifier_chain_register(nh, n, false); +} EXPORT_SYMBOL_GPL(blocking_notifier_chain_register); /** + * blocking_notifier_chain_register_unique_prio - Add notifier to a blocking notifier chain + * @nh: Pointer to head of the blocking notifier chain + * @n: New entry in notifier chain + * + * Adds a notifier to an blocking notifier chain if there is no other + * notifier registered using the same priority. + * + * Returns 0 on success, %-EEXIST or %-EBUSY on error. + */ +int blocking_notifier_chain_register_unique_prio(struct blocking_notifier_head *nh, + struct notifier_block *n) +{ + return __blocking_notifier_chain_register(nh, n, true); +} +EXPORT_SYMBOL_GPL(blocking_notifier_chain_register_unique_prio); + +/** * blocking_notifier_chain_unregister - Remove notifier from a blocking notifier chain * @nh: Pointer to head of the blocking notifier chain * @n: Entry to remove from notifier chain @@ -354,7 +404,7 @@ EXPORT_SYMBOL_GPL(blocking_notifier_call_chain); int raw_notifier_chain_register(struct raw_notifier_head *nh, struct notifier_block *n) { - return notifier_chain_register(&nh->head, n); + return notifier_chain_register(&nh->head, n, false); } EXPORT_SYMBOL_GPL(raw_notifier_chain_register); @@ -433,10 +483,10 @@ int srcu_notifier_chain_register(struct srcu_notifier_head *nh, * such times we must not call mutex_lock(). */ if (unlikely(system_state == SYSTEM_BOOTING)) - return notifier_chain_register(&nh->head, n); + return notifier_chain_register(&nh->head, n, false); mutex_lock(&nh->mutex); - ret = notifier_chain_register(&nh->head, n); + ret = notifier_chain_register(&nh->head, n, false); mutex_unlock(&nh->mutex); return ret; } -- 2.7.4