Docs » Autodocs » exec.library » InitSemaphore
InitSemaphore -- initialize a signal semaphore
InitSemaphore(signalSemaphore)
A0
void InitSemaphore(struct SignalSemaphore *);
This function initializes a signal semaphore and prepares it for
use. It does not allocate anything, but does initialize list
pointers and the semaphore counters.
Semaphores are often used to protect critical data structures
or hardware that can only be accessed by one task at a time.
After initialization, the address of the SignalSemaphore may be
made available to any number of tasks. Typically a task will
try to ObtainSemaphore(), passing this address in. If no other
task owns the semaphore, then the call will lock and return
quickly. If more tasks try to ObtainSemaphore(), they will
be put to sleep. When the owner of the semaphore releases
it, the next waiter in turn will be woken up.
Semaphores are often preferable to the old-style Forbid()/Permit()
type arbitration. With Forbid()/Permit() *all* other tasks are
prevented from running. With semaphores, only those tasks that
need access to whatever the semaphore protects are subject
to waiting.
signalSemaphore -- a signal semaphore structure (with all fields
set to zero before the call)
ObtainSemaphore(), ObtainSemaphoreShared(), AttemptSemaphore(), ReleaseSemaphore(), Procure(), Vacate(), <exec/semaphores.h>
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