Forces the calling kernel thread to wait for the occurrence of a shared event.
#include <sys/types.h> #include <sys/errno.h> #include <sys/sleep.h> int e_sleepl ( lock_word, event_word, flags) int *lock_word; tid_t *event_word; int flags;
| Item | Description |
|---|---|
| lock_word | Specifies the lock word for a conventional process lock. |
| event_word | Specifies the shared event word. The kernel uses this word to anchor the list of kernel threads sleeping on this event. This event word must be initialized to EVENT_NULL before its first use. |
| flags | Specifies the flags that control action on occurrence of a signal. These flags are found in the /usr/include/sys/sleep.h file. |
The e_sleepl kernel service waits for the specified shared event to occur. The kernel places the current kernel thread on the list anchored by the event_word parameter. The e_wakeup service wakes up all threads on the list.
The e_wakeup service does not wake up a thread that is not currently sleeping in the e_sleepl function. That is, if an e_wakeup operation for an event is issued before the thread calls the e_sleepl service for the event, the thread still sleeps, waiting on the next e_wakeup operation for the event. This implies that routines using this capability must ensure that no timing window exists in which events could be missed due to the e_wakeup service being called before the e_sleepl service for the event has been called.
The e_sleepl service also unlocks the conventional lock specified by the lock_word parameter before putting the thread to sleep. It also reacquires the lock when the thread wakes up.
The anchor for the event list, specified by the event_word parameter, must be initialized to EVENT_NULL before its first use. Kernel extensions must not alter this anchor while it is in use.
Values for the flags Parameter
The flags parameter controls how signals affect waiting for an event. There are three flags available to the e_sleepl service:
| Item | Description |
|---|---|
| EVENT_SIGRET | Indicates the termination of the wait for the event by an unmasked signal. The return value is set to EVENT_SIG. |
| EVENT_SIGWAKE | Indicates the termination of the event by an unmasked signal. This flag also indicates the transfer of control to the return from the last setjmpx service with the return value set to EINTR. |
| EVENT_SHORT | Indicates that signals cannot terminate the wait. Use the EVENT_SHORT flag for only short, guaranteed-to-wakeup sleeps. |
The e_sleepl kernel service can be called from the process environment only.
| Item | Description |
|---|---|
| EVENT_SUCC | Indicates successful completion. |
| EVENT_SIG | Indicates that the EVENT_SIGRET flag is set and the wait is terminated by a signal. |