#ifndef _LINUX_NOTIFIER_H
#define _LINUX_NOTIFIER_H
#include <linux/errno.h>
+#include <linux/mutex.h>
+#include <linux/rwsem.h>
+#include <linux/srcu.h>
-struct notifier_block
-{
- int (*notifier_call)(struct notifier_block *self, unsigned long, void *);
+/*
+ * Notifier chains are of four types:
+ *
+ * Atomic notifier chains: Chain callbacks run in interrupt/atomic
+ * context. Callouts are not allowed to block.
+ * Blocking notifier chains: Chain callbacks run in process context.
+ * Callouts are allowed to block.
+ * 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() and srcu_notifier_chain_register()
+ * must be called from a process context. Ditto for the corresponding
+ * _unregister() routines.
+ *
+ * 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 {
+ int (*notifier_call)(struct notifier_block *, unsigned long, void *);
struct notifier_block *next;
int priority;
};
+struct atomic_notifier_head {
+ spinlock_t lock;
+ struct notifier_block *head;
+};
+
+struct blocking_notifier_head {
+ struct rw_semaphore rwsem;
+ struct notifier_block *head;
+};
+
+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; \
+ } while (0)
+#define BLOCKING_INIT_NOTIFIER_HEAD(name) do { \
+ init_rwsem(&(name)->rwsem); \
+ (name)->head = NULL; \
+ } while (0)
+#define RAW_INIT_NOTIFIER_HEAD(name) do { \
+ (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 }
+#define BLOCKING_NOTIFIER_INIT(name) { \
+ .rwsem = __RWSEM_INITIALIZER((name).rwsem), \
+ .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 = \
+ ATOMIC_NOTIFIER_INIT(name)
+#define BLOCKING_NOTIFIER_HEAD(name) \
+ struct blocking_notifier_head name = \
+ BLOCKING_NOTIFIER_INIT(name)
+#define RAW_NOTIFIER_HEAD(name) \
+ struct raw_notifier_head name = \
+ RAW_NOTIFIER_INIT(name)
#ifdef __KERNEL__
-extern int notifier_chain_register(struct notifier_block **list, struct notifier_block *n);
-extern int notifier_chain_unregister(struct notifier_block **nl, struct notifier_block *n);
-extern int notifier_call_chain(struct notifier_block **n, unsigned long val, void *v);
+extern int atomic_notifier_chain_register(struct atomic_notifier_head *,
+ struct notifier_block *);
+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 *);
+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);
+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 */
#define NOTIFY_STOP_MASK 0x8000 /* Don't call further */
-#define NOTIFY_BAD (NOTIFY_STOP_MASK|0x0002) /* Bad/Veto action */
+#define NOTIFY_BAD (NOTIFY_STOP_MASK|0x0002)
+ /* Bad/Veto action */
/*
* Clean way to return from the notifier and stop further calls.
*/
git://git.onelab.eu / linux-2.6.git / blobdiff