diff options
Diffstat (limited to 'kern/sleepq.h')
| -rw-r--r-- | kern/sleepq.h | 31 |
1 files changed, 24 insertions, 7 deletions
diff --git a/kern/sleepq.h b/kern/sleepq.h index 3de765a3..827d0436 100644 --- a/kern/sleepq.h +++ b/kern/sleepq.h @@ -26,17 +26,13 @@ * the associated mutex, at which point two sleep queues are locked. * Handling condition variable sleep queues slightly differently * allows preventing deadlocks while keeping overall complexity low. - * - * In addition, despite being used to implement condition variables, - * this implementation doesn't provide a broadcast call. The rationale - * is to force users to implement "chained waking" in order to avoid - * the thundering herd effect. */ #ifndef _KERN_SLEEPQ_H #define _KERN_SLEEPQ_H #include <stdbool.h> +#include <stdint.h> #include <kern/init.h> @@ -98,7 +94,7 @@ void sleepq_return(struct sleepq *sleepq, unsigned long flags); bool sleepq_empty(const struct sleepq *sleepq); /* - * Wait for a wake up on the given sleep queue. + * Wait for a wake-up on the given sleep queue. * * The sleep queue must be lent when calling this function. It is * released and later reacquired before returning from this function. @@ -110,8 +106,13 @@ bool sleepq_empty(const struct sleepq *sleepq); * the queue, the queue is not immediately considered empty. * * Threads are queued in FIFO order. + * + * When bounding the duration of the wait, the caller must pass an absolute + * time in ticks, and ERROR_TIMEDOUT is returned if that time is reached + * before the sleep queue is signalled. */ void sleepq_wait(struct sleepq *sleepq, const char *wchan); +int sleepq_timedwait(struct sleepq *sleepq, const char *wchan, uint64_t ticks); /* * Wake up a thread waiting on the given sleep queue, if any. @@ -125,10 +126,26 @@ void sleepq_wait(struct sleepq *sleepq, const char *wchan); * * Threads are queued in FIFO order, which means signalling a sleep * queue multiple times always awakens the same thread, regardless - * of new waiters, as long as that first thread didn't reacquire the + * of new waiters, as long as that thread didn't reacquire the * sleep queue. + * + * A broadcast differs only by also making all currently waiting threads + * pending for wake-up. As with sleepq_signal, a single thread may be + * awaken. The rationale is to force users to implement "chained waking" + * in order to avoid the thundering herd effect. */ void sleepq_signal(struct sleepq *sleepq); +void sleepq_broadcast(struct sleepq *sleepq); + +/* + * Wake up a pending thread. + * + * This function may only wake up a thread pending for wake-up after a + * broadcast. It is used to chain wake-ups to avoid the thundering herd + * effect. If there are no threads pending for wake-up, this function + * does nothing. + */ +void sleepq_wakeup(struct sleepq *sleepq); /* * This init operation provides : |