osfmk/man/semaphore_signal.html

   1 <h2>semaphore_signal</h2>
   2 <hr>
   3 <p>
   4 <strong>Function</strong> - Increments the semaphore count.
   5 <h3>SYNOPSIS</h3>
   6 <pre>
   7 <strong>kern_return_t   semaphore_signal</strong>
   8                 <strong>(semaphore_t</strong>                          <var>semaphore</var><strong>);</strong>
   9 </pre>
  10 <h3>PARAMETERS</h3>
  11 <dl>
  12 <p>
  13 <dt> <var>semaphore</var>
  14 <dd>
  15 [in send right] The port naming the semaphore to be signalled.
  16 </dl>
  17 <h3>DESCRIPTION</h3>
  18 <p>
  19 The <strong>semaphore_signal</strong> function increments the semaphore count. If the
  20 count goes non-negative (i.e. greater than or equal to 0) and a thread
  21 is blocked on the semaphore, then the waiting thread is scheduled to
  22 execute. If multiple threads are blocked on the semaphore, the thread
  23 scheduled to execute is selected according to the wakeup policy of the
  24 semaphore (set when the semaphore was created via <strong>semaphore_create</strong>).
  25 Device driver interrupt service routines may safely execute
  26 <strong>semaphore_signal</strong> operations without causing a deadlock.
  27 <h3>RETURN VALUES</h3>
  28 <dl>
  29 <p>
  30 <dt> <strong>KERN_INVALID_ARGUMENT</strong>
  31 <dd>
  32 The specified semaphore is invalid.
  33 <p>
  34 <dt> <strong>KERN_TERMINATED</strong>
  35 <dd>
  36 The specified semaphore has been destroyed.
  37 <p>
  38 <dt> <strong>KERN_SUCCESS</strong>
  39 <dd>
  40 The semaphore has been signalled.
  41 </dl>
  42 <h3>RELATED INFORMATION</h3>
  43 <p>
  44 Functions:
  45 <a href="semaphore_create.html"><strong>semaphore_create</strong></a>,
  46 <a href="semaphore_destroy.html"><strong>semaphore_destroy</strong></a>,
  47 <a href="semaphore_signal_all.html"><strong>semaphore_signal_all</strong></a>,
  48 <a href="semaphore_wait.html"><strong>semaphore_wait</strong></a>,
  49 <a href="device_get_status.html"><strong>device_get_status</strong></a>.