diff options
Diffstat (limited to 'include/linux/wait_bit.h')
| -rw-r--r-- | include/linux/wait_bit.h | 159 |
1 files changed, 86 insertions, 73 deletions
diff --git a/include/linux/wait_bit.h b/include/linux/wait_bit.h index 48e123839892..723e7bf35747 100644 --- a/include/linux/wait_bit.h +++ b/include/linux/wait_bit.h @@ -53,19 +53,21 @@ 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 +82,20 @@ 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(). + * + * 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, 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 %-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 +109,24 @@ 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(). * - * 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. + * This is similar to wait_on_bit(), except it also takes a timeout + * parameter. + * + * 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 +142,21 @@ 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 +169,22 @@ 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 +196,18 @@ 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 +223,19 @@ 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, @@ -320,12 +332,13 @@ do { \ /** * 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, unsigned long *word) { |