diff options
Diffstat (limited to 'include/linux/notifier.h')
| -rw-r--r-- | include/linux/notifier.h | 43 |
1 files changed, 38 insertions, 5 deletions
diff --git a/include/linux/notifier.h b/include/linux/notifier.h index 7ff386a6ae8..10a43ed0527 100644 --- a/include/linux/notifier.h +++ b/include/linux/notifier.h @@ -12,9 +12,10 @@ #include <linux/errno.h> #include <linux/mutex.h> #include <linux/rwsem.h> +#include <linux/srcu.h> /* - * Notifier chains are of three types: + * Notifier chains are of four types: * * Atomic notifier chains: Chain callbacks run in interrupt/atomic * context. Callouts are not allowed to block. @@ -23,13 +24,27 @@ * Raw notifier chains: There are no restrictions on callbacks, * registration, or unregistration. All locking and protection * must be provided by the caller. + * SRCU notifier chains: A variant of blocking notifier chains, with + * the same restrictions. * * atomic_notifier_chain_register() may be called from an atomic context, - * but blocking_notifier_chain_register() must be called from a process - * context. Ditto for the corresponding _unregister() routines. + * but blocking_notifier_chain_register() and srcu_notifier_chain_register() + * must be called from a process context. Ditto for the corresponding + * _unregister() routines. * - * atomic_notifier_chain_unregister() and blocking_notifier_chain_unregister() - * _must not_ be called from within the call chain. + * atomic_notifier_chain_unregister(), blocking_notifier_chain_unregister(), + * and srcu_notifier_chain_unregister() _must not_ be called from within + * the call chain. + * + * SRCU notifier chains are an alternative form of blocking notifier chains. + * They use SRCU (Sleepable Read-Copy Update) instead of rw-semaphores for + * protection of the chain links. This means there is _very_ low overhead + * in srcu_notifier_call_chain(): no cache bounces and no memory barriers. + * As compensation, srcu_notifier_chain_unregister() is rather expensive. + * SRCU notifier chains should be used when the chain will be called very + * often but notifier_blocks will seldom be removed. Also, SRCU notifier + * chains are slightly more difficult to use because they require special + * runtime initialization. */ struct notifier_block { @@ -52,6 +67,12 @@ struct raw_notifier_head { struct notifier_block *head; }; +struct srcu_notifier_head { + struct mutex mutex; + struct srcu_struct srcu; + struct notifier_block *head; +}; + #define ATOMIC_INIT_NOTIFIER_HEAD(name) do { \ spin_lock_init(&(name)->lock); \ (name)->head = NULL; \ @@ -64,6 +85,11 @@ struct raw_notifier_head { (name)->head = NULL; \ } while (0) +/* srcu_notifier_heads must be initialized and cleaned up dynamically */ +extern void srcu_init_notifier_head(struct srcu_notifier_head *nh); +#define srcu_cleanup_notifier_head(name) \ + cleanup_srcu_struct(&(name)->srcu); + #define ATOMIC_NOTIFIER_INIT(name) { \ .lock = __SPIN_LOCK_UNLOCKED(name.lock), \ .head = NULL } @@ -72,6 +98,7 @@ struct raw_notifier_head { .head = NULL } #define RAW_NOTIFIER_INIT(name) { \ .head = NULL } +/* srcu_notifier_heads cannot be initialized statically */ #define ATOMIC_NOTIFIER_HEAD(name) \ struct atomic_notifier_head name = \ @@ -91,6 +118,8 @@ extern int blocking_notifier_chain_register(struct blocking_notifier_head *, struct notifier_block *); extern int raw_notifier_chain_register(struct raw_notifier_head *, struct notifier_block *); +extern int srcu_notifier_chain_register(struct srcu_notifier_head *, + struct notifier_block *); extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *, struct notifier_block *); @@ -98,6 +127,8 @@ extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *, struct notifier_block *); extern int raw_notifier_chain_unregister(struct raw_notifier_head *, struct notifier_block *); +extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *, + struct notifier_block *); extern int atomic_notifier_call_chain(struct atomic_notifier_head *, unsigned long val, void *v); @@ -105,6 +136,8 @@ extern int blocking_notifier_call_chain(struct blocking_notifier_head *, unsigned long val, void *v); extern int raw_notifier_call_chain(struct raw_notifier_head *, unsigned long val, void *v); +extern int srcu_notifier_call_chain(struct srcu_notifier_head *, + unsigned long val, void *v); #define NOTIFY_DONE 0x0000 /* Don't care */ #define NOTIFY_OK 0x0001 /* Suits me */ |