condSignal#

Synopsis#

#include <sys/threads.h>

int condBroadcast(handle_t h);

int condSignal(handle_t h);

Status#

Implemented

Conformance#

Phoenix-RTOS specific

Description#

These functions shall unblock threads blocked on a condition variable.

The condBroadcast() function shall unblock all threads currently blocked on the specified conditional variable h.

The condSignal() function shall unblock at least one of the threads that are blocked on the specified condition variable h (if any threads are blocked on h).

If more than one thread is blocked on a condition variable, the scheduling policy shall determine the order in which threads are unblocked. When each thread unblocked as a result of a condBroadcast() or condSignal() returns from its call to condWait(), the thread shall own the mutex with which it is called condWait(). The thread(s) that are unblocked shall contend for the mutex according to the scheduling policy (if applicable), and as if each had called mutexLock().

The condBroadcast() or condSignal() functions may be called by a thread whether it currently owns the mutex that threads calling condWait() have associated with the condition variable during their waits; however, if predictable scheduling behavior is required, then that mutex shall be locked by the thread calling condBroadcast() or condSignal().

When there is no thread waiting on condition invoking condBroadcast() and condSignal() internal condition state is changed. First condWait invoked on condition exits immediately without waiting. This property is known as being “sticky”. Condition signaling performed on user space interrupt handler is performed without lock acquired. Sticky condition implementation ensures that signals sent without lock can be reliably detected.

The behavior is undefined if the value specified by the cond argument to condBroadcast() or condSignal() does not refer to an initialized condition variable.

Return value#

If successful, the condBroadcast() and condSignal() functions shall return zero; otherwise, an error number shall be returned to indicate the error.

Errors#

The condBroadcast() and condSignal() function may fail if:

  • -EINVAL - The value h does not refer to an initialized condition variable.

  • -EINVAL - Parent process for h variable ceased to exist during function call

These functions shall not return an error code of -EINTR.

Tests#

Untested

Known bugs#

None

See Also#

  1. Standard library functions

  2. Table of Contents