diff options
Diffstat (limited to 'kernel/sys.c')
| -rw-r--r-- | kernel/sys.c | 327 |
1 files changed, 266 insertions, 61 deletions
diff --git a/kernel/sys.c b/kernel/sys.c index 38bc73ede2ba..c93d37f71aef 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -95,99 +95,304 @@ int cad_pid = 1; * and the like. */ -static struct notifier_block *reboot_notifier_list; -static DEFINE_RWLOCK(notifier_lock); +static BLOCKING_NOTIFIER_HEAD(reboot_notifier_list); + +/* + * Notifier chain core routines. The exported routines below + * are layered on top of these, with appropriate locking added. + */ + +static int notifier_chain_register(struct notifier_block **nl, + struct notifier_block *n) +{ + while ((*nl) != NULL) { + if (n->priority > (*nl)->priority) + break; + nl = &((*nl)->next); + } + n->next = *nl; + rcu_assign_pointer(*nl, n); + return 0; +} + +static int notifier_chain_unregister(struct notifier_block **nl, + struct notifier_block *n) +{ + while ((*nl) != NULL) { + if ((*nl) == n) { + rcu_assign_pointer(*nl, n->next); + return 0; + } + nl = &((*nl)->next); + } + return -ENOENT; +} + +static int __kprobes notifier_call_chain(struct notifier_block **nl, + unsigned long val, void *v) +{ + int ret = NOTIFY_DONE; + struct notifier_block *nb; + + nb = rcu_dereference(*nl); + while (nb) { + ret = nb->notifier_call(nb, val, v); + if ((ret & NOTIFY_STOP_MASK) == NOTIFY_STOP_MASK) + break; + nb = rcu_dereference(nb->next); + } + return ret; +} + +/* + * Atomic notifier chain routines. Registration and unregistration + * use a mutex, and call_chain is synchronized by RCU (no locks). + */ /** - * notifier_chain_register - Add notifier to a notifier chain - * @list: Pointer to root list pointer + * atomic_notifier_chain_register - 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 a notifier chain. + * Adds a notifier to an atomic notifier chain. * * Currently always returns zero. */ + +int atomic_notifier_chain_register(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); + spin_unlock_irqrestore(&nh->lock, flags); + return ret; +} + +EXPORT_SYMBOL_GPL(atomic_notifier_chain_register); + +/** + * 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 + * + * Removes a notifier from an atomic notifier chain. + * + * Returns zero on success or %-ENOENT on failure. + */ +int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh, + struct notifier_block *n) +{ + unsigned long flags; + int ret; + + spin_lock_irqsave(&nh->lock, flags); + ret = notifier_chain_unregister(&nh->head, n); + spin_unlock_irqrestore(&nh->lock, flags); + synchronize_rcu(); + return ret; +} + +EXPORT_SYMBOL_GPL(atomic_notifier_chain_unregister); + +/** + * atomic_notifier_call_chain - Call functions in an atomic notifier chain + * @nh: Pointer to head of the atomic notifier chain + * @val: Value passed unmodified to notifier function + * @v: Pointer passed unmodified to notifier function + * + * Calls each function in a notifier chain in turn. The functions + * run in an atomic context, so they must not block. + * This routine uses RCU to synchronize with changes to the chain. + * + * If the return value of the notifier can be and'ed + * with %NOTIFY_STOP_MASK then atomic_notifier_call_chain + * will return immediately, with the return value of + * the notifier function which halted execution. + * Otherwise the return value is the return value + * of the last notifier function called. + */ -int notifier_chain_register(struct notifier_block **list, struct notifier_block *n) +int atomic_notifier_call_chain(struct atomic_notifier_head *nh, + unsigned long val, void *v) { - write_lock(¬ifier_lock); - while(*list) - { - if(n->priority > (*list)->priority) - break; - list= &((*list)->next); - } - n->next = *list; - *list=n; - write_unlock(¬ifier_lock); - return 0; + int ret; + + rcu_read_lock(); + ret = notifier_call_chain(&nh->head, val, v); + rcu_read_unlock(); + return ret; } -EXPORT_SYMBOL(notifier_chain_register); +EXPORT_SYMBOL_GPL(atomic_notifier_call_chain); + +/* + * Blocking notifier chain routines. All access to the chain is + * synchronized by an rwsem. + */ /** - * notifier_chain_unregister - Remove notifier from a notifier chain - * @nl: Pointer to root list pointer + * 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 * - * Removes a notifier from a notifier chain. + * Adds a notifier to a blocking notifier chain. + * Must be called in process context. * - * Returns zero on success, or %-ENOENT on failure. + * Currently always returns zero. */ -int notifier_chain_unregister(struct notifier_block **nl, struct notifier_block *n) +int blocking_notifier_chain_register(struct blocking_notifier_head *nh, + struct notifier_block *n) { - write_lock(¬ifier_lock); - while((*nl)!=NULL) - { - if((*nl)==n) - { - *nl=n->next; - write_unlock(¬ifier_lock); - return 0; - } - nl=&((*nl)->next); - } - write_unlock(¬ifier_lock); - return -ENOENT; + int ret; + + /* + * This code gets used during boot-up, when task switching is + * not yet working and interrupts must remain disabled. At + * such times we must not call down_write(). + */ + if (unlikely(system_state == SYSTEM_BOOTING)) + return notifier_chain_register(&nh->head, n); + + down_write(&nh->rwsem); + ret = notifier_chain_register(&nh->head, n); + up_write(&nh->rwsem); + return ret; } -EXPORT_SYMBOL(notifier_chain_unregister); +EXPORT_SYMBOL_GPL(blocking_notifier_chain_register); /** - * notifier_call_chain - Call functions in a notifier chain - * @n: Pointer to root pointer of notifier chain + * 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 + * + * Removes a notifier from a blocking notifier chain. + * Must be called from process context. + * + * Returns zero on success or %-ENOENT on failure. + */ +int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh, + struct notifier_block *n) +{ + int ret; + + /* + * This code gets used during boot-up, when task switching is + * not yet working and interrupts must remain disabled. At + * such times we must not call down_write(). + */ + if (unlikely(system_state == SYSTEM_BOOTING)) + return notifier_chain_unregister(&nh->head, n); + + down_write(&nh->rwsem); + ret = notifier_chain_unregister(&nh->head, n); + up_write(&nh->rwsem); + return ret; +} + +EXPORT_SYMBOL_GPL(blocking_notifier_chain_unregister); + +/** + * blocking_notifier_call_chain - Call functions in a blocking notifier chain + * @nh: Pointer to head of the blocking notifier chain * @val: Value passed unmodified to notifier function * @v: Pointer passed unmodified to notifier function * - * Calls each function in a notifier chain in turn. + * Calls each function in a notifier chain in turn. The functions + * run in a process context, so they are allowed to block. * - * If the return value of the notifier can be and'd - * with %NOTIFY_STOP_MASK, then notifier_call_chain + * If the return value of the notifier can be and'ed + * with %NOTIFY_STOP_MASK then blocking_notifier_call_chain * will return immediately, with the return value of * the notifier function which halted execution. - * Otherwise, the return value is the return value + * Otherwise the return value is the return value * of the last notifier function called. */ -int __kprobes notifier_call_chain(struct notifier_block **n, unsigned long val, void *v) +int blocking_notifier_call_chain(struct blocking_notifier_head *nh, + unsigned long val, void *v) { - int ret=NOTIFY_DONE; - struct notifier_block *nb = *n; + int ret; - while(nb) - { - ret=nb->notifier_call(nb,val,v); - if(ret&NOTIFY_STOP_MASK) - { - return ret; - } - nb=nb->next; - } + down_read(&nh->rwsem); + ret = notifier_call_chain(&nh->head, val, v); + up_read(&nh->rwsem); return ret; } -EXPORT_SYMBOL(notifier_call_chain); +EXPORT_SYMBOL_GPL(blocking_notifier_call_chain); + +/* + * Raw notifier chain routines. There is no protection; + * the caller must provide it. Use at your own risk! + */ + +/** + * raw_notifier_chain_register - Add notifier to a raw notifier chain + * @nh: Pointer to head of the raw notifier chain + * @n: New entry in notifier chain + * + * Adds a notifier to a raw notifier chain. + * All locking must be provided by the caller. + * + * Currently always returns zero. + */ + +int raw_notifier_chain_register(struct raw_notifier_head *nh, + struct notifier_block *n) +{ + return notifier_chain_register(&nh->head, n); +} + +EXPORT_SYMBOL_GPL(raw_notifier_chain_register); + +/** + * raw_notifier_chain_unregister - Remove notifier from a raw notifier chain + * @nh: Pointer to head of the raw notifier chain + * @n: Entry to remove from notifier chain + * + * Removes a notifier from a raw notifier chain. + * All locking must be provided by the caller. + * + * Returns zero on success or %-ENOENT on failure. + */ +int raw_notifier_chain_unregister(struct raw_notifier_head *nh, + struct notifier_block *n) +{ + return notifier_chain_unregister(&nh->head, n); +} + +EXPORT_SYMBOL_GPL(raw_notifier_chain_unregister); + +/** + * raw_notifier_call_chain - Call functions in a raw notifier chain + * @nh: Pointer to head of the raw notifier chain + * @val: Value passed unmodified to notifier function + * @v: Pointer passed unmodified to notifier function + * + * Calls each function in a notifier chain in turn. The functions + * run in an undefined context. + * All locking must be provided by the caller. + * + * If the return value of the notifier can be and'ed + * with %NOTIFY_STOP_MASK then raw_notifier_call_chain + * will return immediately, with the return value of + * the notifier function which halted execution. + * Otherwise the return value is the return value + * of the last notifier function called. + */ + +int raw_notifier_call_chain(struct raw_notifier_head *nh, + unsigned long val, void *v) +{ + return notifier_call_chain(&nh->head, val, v); +} + +EXPORT_SYMBOL_GPL(raw_notifier_call_chain); /** * register_reboot_notifier - Register function to be called at reboot time @@ -196,13 +401,13 @@ EXPORT_SYMBOL(notifier_call_chain); * Registers a function with the list of functions * to be called at reboot time. * - * Currently always returns zero, as notifier_chain_register + * Currently always returns zero, as blocking_notifier_chain_register * always returns zero. */ int register_reboot_notifier(struct notifier_block * nb) { - return notifier_chain_register(&reboot_notifier_list, nb); + return blocking_notifier_chain_register(&reboot_notifier_list, nb); } EXPORT_SYMBOL(register_reboot_notifier); @@ -219,7 +424,7 @@ EXPORT_SYMBOL(register_reboot_notifier); int unregister_reboot_notifier(struct notifier_block * nb) { - return notifier_chain_unregister(&reboot_notifier_list, nb); + return blocking_notifier_chain_unregister(&reboot_notifier_list, nb); } EXPORT_SYMBOL(unregister_reboot_notifier); @@ -380,7 +585,7 @@ EXPORT_SYMBOL_GPL(emergency_restart); void kernel_restart_prepare(char *cmd) { - notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd); + blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd); system_state = SYSTEM_RESTART; device_shutdown(); } @@ -430,7 +635,7 @@ EXPORT_SYMBOL_GPL(kernel_kexec); void kernel_shutdown_prepare(enum system_states state) { - notifier_call_chain(&reboot_notifier_list, + blocking_notifier_call_chain(&reboot_notifier_list, (state == SYSTEM_HALT)?SYS_HALT:SYS_POWER_OFF, NULL); system_state = state; device_shutdown(); |