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/*
* Routines to manage notifier chains for passing status changes to any
* interested routines. We need this instead of hard coded call lists so
* that modules can poke their nose into the innards. The network devices
* needed them so here they are for the rest of you.
*
* Alan Cox <Alan.Cox@linux.org>
*/
#ifndef _LINUX_NOTIFIER_H
#define _LINUX_NOTIFIER_H
#include <linux/errno.h>
#include <linux/mutex.h>
#include <linux/rwsem.h>
#include <linux/srcu.h>
/*
* 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 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 */
/*
* Clean way to return from the notifier and stop further calls.
*/
#define NOTIFY_STOP (NOTIFY_OK|NOTIFY_STOP_MASK)
/*
* Declared notifiers so far. I can imagine quite a few more chains
* over time (eg laptop power reset chains, reboot chain (to clean
* device units up), device [un]mount chain, module load/unload chain,
* low memory chain, screenblank chain (for plug in modular screenblankers)
* VC switch chains (for loadable kernel svgalib VC switch helpers) etc...
*/
/* netdevice notifier chain */
#define NETDEV_UP 0x0001 /* For now you can't veto a device up/down */
#define NETDEV_DOWN 0x0002
#define NETDEV_REBOOT 0x0003 /* Tell a protocol stack a network interface
detected a hardware crash and restarted
- we can use this eg to kick tcp sessions
once done */
#define NETDEV_CHANGE 0x0004 /* Notify device state change */
#define NETDEV_REGISTER 0x0005
#define NETDEV_UNREGISTER 0x0006
#define NETDEV_CHANGEMTU 0x0007
#define NETDEV_CHANGEADDR 0x0008
#define NETDEV_GOING_DOWN 0x0009
#define NETDEV_CHANGENAME 0x000A
#define NETDEV_FEAT_CHANGE 0x000B
#define SYS_DOWN 0x0001 /* Notify of system down */
#define SYS_RESTART SYS_DOWN
#define SYS_HALT 0x0002 /* Notify of system halt */
#define SYS_POWER_OFF 0x0003 /* Notify of system power off */
#define NETLINK_URELEASE 0x0001 /* Unicast netlink socket released */
#define CPU_ONLINE 0x0002 /* CPU (unsigned)v is up */
#define CPU_UP_PREPARE 0x0003 /* CPU (unsigned)v coming up */
#define CPU_UP_CANCELED 0x0004 /* CPU (unsigned)v NOT coming up */
#define CPU_DOWN_PREPARE 0x0005 /* CPU (unsigned)v going down */
#define CPU_DOWN_FAILED 0x0006 /* CPU (unsigned)v NOT going down */
#define CPU_DEAD 0x0007 /* CPU (unsigned)v dead */
#endif /* __KERNEL__ */
#endif /* _LINUX_NOTIFIER_H */
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