diff options
Diffstat (limited to 'include/linux/wait_bit.h')
| -rw-r--r-- | include/linux/wait_bit.h | 444 |
1 files changed, 362 insertions, 82 deletions
diff --git a/include/linux/wait_bit.h b/include/linux/wait_bit.h index 7725b7579b78..9e29d79fc790 100644 --- a/include/linux/wait_bit.h +++ b/include/linux/wait_bit.h @@ -8,7 +8,7 @@ #include <linux/wait.h> struct wait_bit_key { - void *flags; + unsigned long *flags; int bit_nr; unsigned long timeout; }; @@ -23,14 +23,14 @@ struct wait_bit_queue_entry { typedef int wait_bit_action_f(struct wait_bit_key *key, int mode); -void __wake_up_bit(struct wait_queue_head *wq_head, void *word, int bit); +void __wake_up_bit(struct wait_queue_head *wq_head, unsigned long *word, int bit); int __wait_on_bit(struct wait_queue_head *wq_head, struct wait_bit_queue_entry *wbq_entry, wait_bit_action_f *action, unsigned int mode); int __wait_on_bit_lock(struct wait_queue_head *wq_head, struct wait_bit_queue_entry *wbq_entry, wait_bit_action_f *action, unsigned int mode); -void wake_up_bit(void *word, int bit); -int out_of_line_wait_on_bit(void *word, int, wait_bit_action_f *action, unsigned int mode); -int out_of_line_wait_on_bit_timeout(void *word, int, wait_bit_action_f *action, unsigned int mode, unsigned long timeout); -int out_of_line_wait_on_bit_lock(void *word, int, wait_bit_action_f *action, unsigned int mode); -struct wait_queue_head *bit_waitqueue(void *word, int bit); +void wake_up_bit(unsigned long *word, int bit); +int out_of_line_wait_on_bit(unsigned long *word, int, wait_bit_action_f *action, unsigned int mode); +int out_of_line_wait_on_bit_timeout(unsigned long *word, int, wait_bit_action_f *action, unsigned int mode, unsigned long timeout); +int out_of_line_wait_on_bit_lock(unsigned long *word, int, wait_bit_action_f *action, unsigned int mode); +struct wait_queue_head *bit_waitqueue(unsigned long *word, int bit); extern void __init wait_bit_init(void); int wake_bit_function(struct wait_queue_entry *wq_entry, unsigned mode, int sync, void *key); @@ -49,23 +49,24 @@ int wake_bit_function(struct wait_queue_entry *wq_entry, unsigned mode, int sync extern int bit_wait(struct wait_bit_key *key, int mode); extern int bit_wait_io(struct wait_bit_key *key, int mode); extern int bit_wait_timeout(struct wait_bit_key *key, int mode); -extern int bit_wait_io_timeout(struct wait_bit_key *key, int mode); /** * wait_on_bit - wait for a bit to be cleared - * @word: the word being waited on, a kernel virtual address - * @bit: the bit of the word being waited on + * @word: the address containing the bit being waited on + * @bit: the bit at that address being waited on * @mode: the task state to sleep in * - * There is a standard hashed waitqueue table for generic use. This - * is the part of the hashtable's accessor API that waits on a bit. - * For instance, if one were to have waiters on a bitflag, one would - * call wait_on_bit() in threads waiting for the bit to clear. - * One uses wait_on_bit() where one is waiting for the bit to clear, - * but has no intention of setting it. - * Returned value will be zero if the bit was cleared, or non-zero - * if the process received a signal and the mode permitted wakeup - * on that signal. + * Wait for the given bit in an unsigned long or bitmap (see DECLARE_BITMAP()) + * to be cleared. The clearing of the bit must be signalled with + * wake_up_bit(), often as clear_and_wake_up_bit(). + * + * The process will wait on a waitqueue selected by hash from a shared + * pool. It will only be woken on a wake_up for the target bit, even + * if other processes on the same queue are waiting for other bits. + * + * Returned value will be zero if the bit was cleared in which case the + * call has ACQUIRE semantics, or %-EINTR if the process received a + * signal and the mode permitted wake up on that signal. */ static inline int wait_on_bit(unsigned long *word, int bit, unsigned mode) @@ -80,17 +81,20 @@ wait_on_bit(unsigned long *word, int bit, unsigned mode) /** * wait_on_bit_io - wait for a bit to be cleared - * @word: the word being waited on, a kernel virtual address - * @bit: the bit of the word being waited on + * @word: the address containing the bit being waited on + * @bit: the bit at that address being waited on * @mode: the task state to sleep in * - * Use the standard hashed waitqueue table to wait for a bit - * to be cleared. This is similar to wait_on_bit(), but calls - * io_schedule() instead of schedule() for the actual waiting. + * Wait for the given bit in an unsigned long or bitmap (see DECLARE_BITMAP()) + * to be cleared. The clearing of the bit must be signalled with + * wake_up_bit(), often as clear_and_wake_up_bit(). * - * Returned value will be zero if the bit was cleared, or non-zero - * if the process received a signal and the mode permitted wakeup - * on that signal. + * This is similar to wait_on_bit(), but calls io_schedule() instead of + * schedule() for the actual waiting. + * + * Returned value will be zero if the bit was cleared in which case the + * call has ACQUIRE semantics, or %-EINTR if the process received a + * signal and the mode permitted wake up on that signal. */ static inline int wait_on_bit_io(unsigned long *word, int bit, unsigned mode) @@ -104,19 +108,24 @@ wait_on_bit_io(unsigned long *word, int bit, unsigned mode) } /** - * wait_on_bit_timeout - wait for a bit to be cleared or a timeout elapses - * @word: the word being waited on, a kernel virtual address - * @bit: the bit of the word being waited on + * wait_on_bit_timeout - wait for a bit to be cleared or a timeout to elapse + * @word: the address containing the bit being waited on + * @bit: the bit at that address being waited on * @mode: the task state to sleep in * @timeout: timeout, in jiffies * - * Use the standard hashed waitqueue table to wait for a bit - * to be cleared. This is similar to wait_on_bit(), except also takes a - * timeout parameter. + * Wait for the given bit in an unsigned long or bitmap (see + * DECLARE_BITMAP()) to be cleared, or for a timeout to expire. The + * clearing of the bit must be signalled with wake_up_bit(), often as + * clear_and_wake_up_bit(). + * + * This is similar to wait_on_bit(), except it also takes a timeout + * parameter. * - * Returned value will be zero if the bit was cleared before the - * @timeout elapsed, or non-zero if the @timeout elapsed or process - * received a signal and the mode permitted wakeup on that signal. + * Returned value will be zero if the bit was cleared in which case the + * call has ACQUIRE semantics, or %-EINTR if the process received a + * signal and the mode permitted wake up on that signal, or %-EAGAIN if the + * timeout elapsed. */ static inline int wait_on_bit_timeout(unsigned long *word, int bit, unsigned mode, @@ -132,19 +141,21 @@ wait_on_bit_timeout(unsigned long *word, int bit, unsigned mode, /** * wait_on_bit_action - wait for a bit to be cleared - * @word: the word being waited on, a kernel virtual address - * @bit: the bit of the word being waited on + * @word: the address containing the bit waited on + * @bit: the bit at that address being waited on * @action: the function used to sleep, which may take special actions * @mode: the task state to sleep in * - * Use the standard hashed waitqueue table to wait for a bit - * to be cleared, and allow the waiting action to be specified. - * This is like wait_on_bit() but allows fine control of how the waiting - * is done. + * Wait for the given bit in an unsigned long or bitmap (see DECLARE_BITMAP()) + * to be cleared. The clearing of the bit must be signalled with + * wake_up_bit(), often as clear_and_wake_up_bit(). + * + * This is similar to wait_on_bit(), but calls @action() instead of + * schedule() for the actual waiting. * - * Returned value will be zero if the bit was cleared, or non-zero - * if the process received a signal and the mode permitted wakeup - * on that signal. + * Returned value will be zero if the bit was cleared in which case the + * call has ACQUIRE semantics, or the error code returned by @action if + * that call returned non-zero. */ static inline int wait_on_bit_action(unsigned long *word, int bit, wait_bit_action_f *action, @@ -157,23 +168,22 @@ wait_on_bit_action(unsigned long *word, int bit, wait_bit_action_f *action, } /** - * wait_on_bit_lock - wait for a bit to be cleared, when wanting to set it - * @word: the word being waited on, a kernel virtual address - * @bit: the bit of the word being waited on + * wait_on_bit_lock - wait for a bit to be cleared, then set it + * @word: the address containing the bit being waited on + * @bit: the bit of the word being waited on and set * @mode: the task state to sleep in * - * There is a standard hashed waitqueue table for generic use. This - * is the part of the hashtable's accessor API that waits on a bit - * when one intends to set it, for instance, trying to lock bitflags. - * For instance, if one were to have waiters trying to set bitflag - * and waiting for it to clear before setting it, one would call - * wait_on_bit() in threads waiting to be able to set the bit. - * One uses wait_on_bit_lock() where one is waiting for the bit to - * clear with the intention of setting it, and when done, clearing it. + * Wait for the given bit in an unsigned long or bitmap (see + * DECLARE_BITMAP()) to be cleared. The clearing of the bit must be + * signalled with wake_up_bit(), often as clear_and_wake_up_bit(). As + * soon as it is clear, atomically set it and return. * - * Returns zero if the bit was (eventually) found to be clear and was - * set. Returns non-zero if a signal was delivered to the process and - * the @mode allows that signal to wake the process. + * This is similar to wait_on_bit(), but sets the bit before returning. + * + * Returned value will be zero if the bit was successfully set in which + * case the call has the same memory sequencing semantics as + * test_and_clear_bit(), or %-EINTR if the process received a signal and + * the mode permitted wake up on that signal. */ static inline int wait_on_bit_lock(unsigned long *word, int bit, unsigned mode) @@ -185,15 +195,18 @@ wait_on_bit_lock(unsigned long *word, int bit, unsigned mode) } /** - * wait_on_bit_lock_io - wait for a bit to be cleared, when wanting to set it - * @word: the word being waited on, a kernel virtual address - * @bit: the bit of the word being waited on + * wait_on_bit_lock_io - wait for a bit to be cleared, then set it + * @word: the address containing the bit being waited on + * @bit: the bit of the word being waited on and set * @mode: the task state to sleep in * - * Use the standard hashed waitqueue table to wait for a bit - * to be cleared and then to atomically set it. This is similar - * to wait_on_bit(), but calls io_schedule() instead of schedule() - * for the actual waiting. + * Wait for the given bit in an unsigned long or bitmap (see + * DECLARE_BITMAP()) to be cleared. The clearing of the bit must be + * signalled with wake_up_bit(), often as clear_and_wake_up_bit(). As + * soon as it is clear, atomically set it and return. + * + * This is similar to wait_on_bit_lock(), but calls io_schedule() instead + * of schedule(). * * Returns zero if the bit was (eventually) found to be clear and was * set. Returns non-zero if a signal was delivered to the process and @@ -209,21 +222,19 @@ wait_on_bit_lock_io(unsigned long *word, int bit, unsigned mode) } /** - * wait_on_bit_lock_action - wait for a bit to be cleared, when wanting to set it - * @word: the word being waited on, a kernel virtual address - * @bit: the bit of the word being waited on + * wait_on_bit_lock_action - wait for a bit to be cleared, then set it + * @word: the address containing the bit being waited on + * @bit: the bit of the word being waited on and set * @action: the function used to sleep, which may take special actions * @mode: the task state to sleep in * - * Use the standard hashed waitqueue table to wait for a bit - * to be cleared and then to set it, and allow the waiting action - * to be specified. - * This is like wait_on_bit() but allows fine control of how the waiting - * is done. + * This is similar to wait_on_bit_lock(), but calls @action() instead of + * schedule() for the actual waiting. * - * Returns zero if the bit was (eventually) found to be clear and was - * set. Returns non-zero if a signal was delivered to the process and - * the @mode allows that signal to wake the process. + * Returned value will be zero if the bit was successfully set in which + * case the call has the same memory sequencing semantics as + * test_and_clear_bit(), or the error code returned by @action if that + * call returned non-zero. */ static inline int wait_on_bit_lock_action(unsigned long *word, int bit, wait_bit_action_f *action, @@ -269,7 +280,26 @@ __out: __ret; \ #define __wait_var_event(var, condition) \ ___wait_var_event(var, condition, TASK_UNINTERRUPTIBLE, 0, 0, \ schedule()) +#define __wait_var_event_io(var, condition) \ + ___wait_var_event(var, condition, TASK_UNINTERRUPTIBLE, 0, 0, \ + io_schedule()) +/** + * wait_var_event - wait for a variable to be updated and notified + * @var: the address of variable being waited on + * @condition: the condition to wait for + * + * Wait for a @condition to be true, only re-checking when a wake up is + * received for the given @var (an arbitrary kernel address which need + * not be directly related to the given condition, but usually is). + * + * The process will wait on a waitqueue selected by hash from a shared + * pool. It will only be woken on a wake_up for the given address. + * + * The condition should normally use smp_load_acquire() or a similarly + * ordered access to ensure that any changes to memory made before the + * condition became true will be visible after the wait completes. + */ #define wait_var_event(var, condition) \ do { \ might_sleep(); \ @@ -278,10 +308,56 @@ do { \ __wait_var_event(var, condition); \ } while (0) +/** + * wait_var_event_io - wait for a variable to be updated and notified + * @var: the address of variable being waited on + * @condition: the condition to wait for + * + * Wait for an IO related @condition to be true, only re-checking when a + * wake up is received for the given @var (an arbitrary kernel address + * which need not be directly related to the given condition, but + * usually is). + * + * The process will wait on a waitqueue selected by hash from a shared + * pool. It will only be woken on a wake_up for the given address. + * + * This is similar to wait_var_event(), but calls io_schedule() instead + * of schedule(). + * + * The condition should normally use smp_load_acquire() or a similarly + * ordered access to ensure that any changes to memory made before the + * condition became true will be visible after the wait completes. + */ +#define wait_var_event_io(var, condition) \ +do { \ + might_sleep(); \ + if (condition) \ + break; \ + __wait_var_event_io(var, condition); \ +} while (0) + #define __wait_var_event_killable(var, condition) \ ___wait_var_event(var, condition, TASK_KILLABLE, 0, 0, \ schedule()) +/** + * wait_var_event_killable - wait for a variable to be updated and notified + * @var: the address of variable being waited on + * @condition: the condition to wait for + * + * Wait for a @condition to be true or a fatal signal to be received, + * only re-checking the condition when a wake up is received for the given + * @var (an arbitrary kernel address which need not be directly related + * to the given condition, but usually is). + * + * This is similar to wait_var_event() but returns a value which is + * 0 if the condition became true, or %-ERESTARTSYS if a fatal signal + * was received. + * + * The condition should normally use smp_load_acquire() or a similarly + * ordered access to ensure that any changes to memory made before the + * condition became true will be visible after the wait completes. + */ #define wait_var_event_killable(var, condition) \ ({ \ int __ret = 0; \ @@ -296,6 +372,26 @@ do { \ TASK_UNINTERRUPTIBLE, 0, timeout, \ __ret = schedule_timeout(__ret)) +/** + * wait_var_event_timeout - wait for a variable to be updated or a timeout to expire + * @var: the address of variable being waited on + * @condition: the condition to wait for + * @timeout: maximum time to wait in jiffies + * + * Wait for a @condition to be true or a timeout to expire, only + * re-checking the condition when a wake up is received for the given + * @var (an arbitrary kernel address which need not be directly related + * to the given condition, but usually is). + * + * This is similar to wait_var_event() but returns a value which is 0 if + * the timeout expired and the condition was still false, or the + * remaining time left in the timeout (but at least 1) if the condition + * was found to be true. + * + * The condition should normally use smp_load_acquire() or a similarly + * ordered access to ensure that any changes to memory made before the + * condition became true will be visible after the wait completes. + */ #define wait_var_event_timeout(var, condition, timeout) \ ({ \ long __ret = timeout; \ @@ -309,6 +405,23 @@ do { \ ___wait_var_event(var, condition, TASK_INTERRUPTIBLE, 0, 0, \ schedule()) +/** + * wait_var_event_killable - wait for a variable to be updated and notified + * @var: the address of variable being waited on + * @condition: the condition to wait for + * + * Wait for a @condition to be true or a signal to be received, only + * re-checking the condition when a wake up is received for the given + * @var (an arbitrary kernel address which need not be directly related + * to the given condition, but usually is). + * + * This is similar to wait_var_event() but returns a value which is 0 if + * the condition became true, or %-ERESTARTSYS if a signal was received. + * + * The condition should normally use smp_load_acquire() or a similarly + * ordered access to ensure that any changes to memory made before the + * condition became true will be visible after the wait completes. + */ #define wait_var_event_interruptible(var, condition) \ ({ \ int __ret = 0; \ @@ -319,15 +432,122 @@ do { \ }) /** - * clear_and_wake_up_bit - clear a bit and wake up anyone waiting on that bit + * wait_var_event_any_lock - wait for a variable to be updated under a lock + * @var: the address of the variable being waited on + * @condition: condition to wait for + * @lock: the object that is locked to protect updates to the variable + * @type: prefix on lock and unlock operations + * @state: waiting state, %TASK_UNINTERRUPTIBLE etc. + * + * Wait for a condition which can only be reliably tested while holding + * a lock. The variables assessed in the condition will normal be updated + * under the same lock, and the wake up should be signalled with + * wake_up_var_locked() under the same lock. + * + * This is similar to wait_var_event(), but assumes a lock is held + * while calling this function and while updating the variable. * + * This must be called while the given lock is held and the lock will be + * dropped when schedule() is called to wait for a wake up, and will be + * reclaimed before testing the condition again. The functions used to + * unlock and lock the object are constructed by appending _unlock and _lock + * to @type. + * + * Return %-ERESTARTSYS if a signal arrives which is allowed to interrupt + * the wait according to @state. + */ +#define wait_var_event_any_lock(var, condition, lock, type, state) \ +({ \ + int __ret = 0; \ + if (!(condition)) \ + __ret = ___wait_var_event(var, condition, state, 0, 0, \ + type ## _unlock(lock); \ + schedule(); \ + type ## _lock(lock)); \ + __ret; \ +}) + +/** + * wait_var_event_spinlock - wait for a variable to be updated under a spinlock + * @var: the address of the variable being waited on + * @condition: condition to wait for + * @lock: the spinlock which protects updates to the variable + * + * Wait for a condition which can only be reliably tested while holding + * a spinlock. The variables assessed in the condition will normal be updated + * under the same spinlock, and the wake up should be signalled with + * wake_up_var_locked() under the same spinlock. + * + * This is similar to wait_var_event(), but assumes a spinlock is held + * while calling this function and while updating the variable. + * + * This must be called while the given lock is held and the lock will be + * dropped when schedule() is called to wait for a wake up, and will be + * reclaimed before testing the condition again. + */ +#define wait_var_event_spinlock(var, condition, lock) \ + wait_var_event_any_lock(var, condition, lock, spin, TASK_UNINTERRUPTIBLE) + +/** + * wait_var_event_mutex - wait for a variable to be updated under a mutex + * @var: the address of the variable being waited on + * @condition: condition to wait for + * @mutex: the mutex which protects updates to the variable + * + * Wait for a condition which can only be reliably tested while holding + * a mutex. The variables assessed in the condition will normal be + * updated under the same mutex, and the wake up should be signalled + * with wake_up_var_locked() under the same mutex. + * + * This is similar to wait_var_event(), but assumes a mutex is held + * while calling this function and while updating the variable. + * + * This must be called while the given mutex is held and the mutex will be + * dropped when schedule() is called to wait for a wake up, and will be + * reclaimed before testing the condition again. + */ +#define wait_var_event_mutex(var, condition, lock) \ + wait_var_event_any_lock(var, condition, lock, mutex, TASK_UNINTERRUPTIBLE) + +/** + * wake_up_var_protected - wake up waiters for a variable asserting that it is safe + * @var: the address of the variable being waited on + * @cond: the condition which afirms this is safe + * + * When waking waiters which use wait_var_event_any_lock() the waker must be + * holding the reelvant lock to avoid races. This version of wake_up_var() + * asserts that the relevant lock is held and so no barrier is needed. + * The @cond is only tested when CONFIG_LOCKDEP is enabled. + */ +#define wake_up_var_protected(var, cond) \ +do { \ + lockdep_assert(cond); \ + wake_up_var(var); \ +} while (0) + +/** + * wake_up_var_locked - wake up waiters for a variable while holding a spinlock or mutex + * @var: the address of the variable being waited on + * @lock: The spinlock or mutex what protects the variable + * + * Send a wake up for the given variable which should be waited for with + * wait_var_event_spinlock() or wait_var_event_mutex(). Unlike wake_up_var(), + * no extra barriers are needed as the locking provides sufficient sequencing. + */ +#define wake_up_var_locked(var, lock) \ + wake_up_var_protected(var, lockdep_is_held(lock)) + +/** + * clear_and_wake_up_bit - clear a bit and wake up anyone waiting on that bit * @bit: the bit of the word being waited on - * @word: the word being waited on, a kernel virtual address + * @word: the address containing the bit being waited on * - * You can use this helper if bitflags are manipulated atomically rather than - * non-atomically under a lock. + * The designated bit is cleared and any tasks waiting in wait_on_bit() + * or similar will be woken. This call has RELEASE semantics so that + * any changes to memory made before this call are guaranteed to be visible + * after the corresponding wait_on_bit() completes. */ -static inline void clear_and_wake_up_bit(int bit, void *word) +static inline void clear_and_wake_up_bit(int bit, unsigned long *word) { clear_bit_unlock(bit, word); /* See wake_up_bit() for which memory barrier you need to use. */ @@ -335,4 +555,64 @@ static inline void clear_and_wake_up_bit(int bit, void *word) wake_up_bit(word, bit); } +/** + * test_and_clear_wake_up_bit - clear a bit if it was set: wake up anyone waiting on that bit + * @bit: the bit of the word being waited on + * @word: the address of memory containing that bit + * + * If the bit is set and can be atomically cleared, any tasks waiting in + * wait_on_bit() or similar will be woken. This call has the same + * complete ordering semantics as test_and_clear_bit(). Any changes to + * memory made before this call are guaranteed to be visible after the + * corresponding wait_on_bit() completes. + * + * Returns %true if the bit was successfully set and the wake up was sent. + */ +static inline bool test_and_clear_wake_up_bit(int bit, unsigned long *word) +{ + if (!test_and_clear_bit(bit, word)) + return false; + /* no extra barrier required */ + wake_up_bit(word, bit); + return true; +} + +/** + * atomic_dec_and_wake_up - decrement an atomic_t and if zero, wake up waiters + * @var: the variable to dec and test + * + * Decrements the atomic variable and if it reaches zero, send a wake_up to any + * processes waiting on the variable. + * + * This function has the same complete ordering semantics as atomic_dec_and_test. + * + * Returns %true is the variable reaches zero and the wake up was sent. + */ + +static inline bool atomic_dec_and_wake_up(atomic_t *var) +{ + if (!atomic_dec_and_test(var)) + return false; + /* No extra barrier required */ + wake_up_var(var); + return true; +} + +/** + * store_release_wake_up - update a variable and send a wake_up + * @var: the address of the variable to be updated and woken + * @val: the value to store in the variable. + * + * Store the given value in the variable send a wake up to any tasks + * waiting on the variable. All necessary barriers are included to ensure + * the task calling wait_var_event() sees the new value and all values + * written to memory before this call. + */ +#define store_release_wake_up(var, val) \ +do { \ + smp_store_release(var, val); \ + smp_mb(); \ + wake_up_var(var); \ +} while (0) + #endif /* _LINUX_WAIT_BIT_H */ |