1*c54f35caSApple OSS Distributions<h2>semaphore_create</h2> 2*c54f35caSApple OSS Distributions<hr> 3*c54f35caSApple OSS Distributions<p> 4*c54f35caSApple OSS Distributions<strong>Function</strong> - Create a new semaphore. 5*c54f35caSApple OSS Distributions<h3>SYNOPSIS</h3> 6*c54f35caSApple OSS Distributions<pre> 7*c54f35caSApple OSS Distributions<strong>kern_return_t semaphore_create</strong> 8*c54f35caSApple OSS Distributions <strong>(task_t</strong> <var>task</var>, 9*c54f35caSApple OSS Distributions <strong>semaphore_t</strong> <var>*semaphore</var>, 10*c54f35caSApple OSS Distributions <strong>int</strong> <var>policy</var>, 11*c54f35caSApple OSS Distributions <strong>int</strong> <var>value</var><strong>);</strong> 12*c54f35caSApple OSS Distributions</pre> 13*c54f35caSApple OSS Distributions<h3>PARAMETERS</h3> 14*c54f35caSApple OSS Distributions<dl> 15*c54f35caSApple OSS Distributions<dt> <var>task</var> 16*c54f35caSApple OSS Distributions<dd> 17*c54f35caSApple OSS Distributions[in task port] The task receiving the send right of the newly created semaphore. 18*c54f35caSApple OSS Distributions<p> 19*c54f35caSApple OSS Distributions<dt> <var>semaphore</var> 20*c54f35caSApple OSS Distributions<dd> 21*c54f35caSApple OSS Distributions[out send right] The port naming the created semaphore. 22*c54f35caSApple OSS Distributions<p> 23*c54f35caSApple OSS Distributions<dt> <var>policy</var> 24*c54f35caSApple OSS Distributions<dd> 25*c54f35caSApple OSS Distributions[in scalar] The blocked thread wakeup policy for the newly created semaphore. Valid policies are: 26*c54f35caSApple OSS Distributions<dl> 27*c54f35caSApple OSS Distributions<p> 28*c54f35caSApple OSS Distributions <dt> SYNC_POLICY_FIFO 29*c54f35caSApple OSS Distributions<dd> 30*c54f35caSApple OSS Distributionsa first-in-first-out policy for scheduling thread wakeup. 31*c54f35caSApple OSS Distributions <p> 32*c54f35caSApple OSS Distributions <dt> SYNC_POLICY_FIXED_PRIORITY 33*c54f35caSApple OSS Distributions<dd> 34*c54f35caSApple OSS Distributionsa fixed priority policy for scheduling thread wakeup. 35*c54f35caSApple OSS Distributions </dl> 36*c54f35caSApple OSS Distributions <p> 37*c54f35caSApple OSS Distributions<dt> <var>value</var> 38*c54f35caSApple OSS Distributions<dd> 39*c54f35caSApple OSS Distributions[in scalar] The initial value of the semaphore count. 40*c54f35caSApple OSS Distributions</dl> 41*c54f35caSApple OSS Distributions<h3>DESCRIPTION</h3> 42*c54f35caSApple OSS Distributions<p> 43*c54f35caSApple OSS DistributionsThe <strong>semaphore_create</strong> function creates a new semaphore, associates the 44*c54f35caSApple OSS Distributionscreated semaphore with the specified task, and returns a send right 45*c54f35caSApple OSS Distributionsnaming the new semaphore. In order to support a robust 46*c54f35caSApple OSS Distributionsproducer/consumer communication service, Interrupt Service Routines 47*c54f35caSApple OSS Distributions(ISR) must be able to signal semaphores. The semaphore synchronizer 48*c54f35caSApple OSS Distributionsservice is designed to allow user-level device drivers to perform 49*c54f35caSApple OSS Distributionssignal operations, eliminating the need for event counters. Device 50*c54f35caSApple OSS Distributionsdrivers which utilize semaphores are responsible for creating (via 51*c54f35caSApple OSS Distributions<strong>semaphore_create</strong>) and exporting (via <strong>device_get_status</strong>) 52*c54f35caSApple OSS Distributionssemaphores for 53*c54f35caSApple OSS Distributionsuser level access. Device driver semaphore creation is done at device 54*c54f35caSApple OSS Distributionsinitialization time. Device drivers may support multiple semaphores. 55*c54f35caSApple OSS Distributions<h3>RETURN VALUES</h3> 56*c54f35caSApple OSS Distributions<dl> 57*c54f35caSApple OSS Distributions <p> 58*c54f35caSApple OSS Distributions<dt> <strong>KERN_INVALID_ARGUMENT</strong> 59*c54f35caSApple OSS Distributions<dd> 60*c54f35caSApple OSS DistributionsThe task argument or the policy argument was invalid, 61*c54f35caSApple OSS Distributions or the initial value of the semaphore was invalid. 62*c54f35caSApple OSS Distributions <p> 63*c54f35caSApple OSS Distributions<dt> <strong>KERN_RESOURCE_SHORTAGE</strong> 64*c54f35caSApple OSS Distributions<dd> 65*c54f35caSApple OSS DistributionsThe kernel could not allocate the semaphore. 66*c54f35caSApple OSS Distributions <p> 67*c54f35caSApple OSS Distributions<dt> <strong>KERN_SUCCESS</strong> 68*c54f35caSApple OSS Distributions<dd> 69*c54f35caSApple OSS DistributionsThe semaphore was successfully created. 70*c54f35caSApple OSS Distributions</dl> 71*c54f35caSApple OSS Distributions<h3>RELATED INFORMATION</h3> 72*c54f35caSApple OSS Distributions<p> 73*c54f35caSApple OSS DistributionsFunctions: 74*c54f35caSApple OSS Distributions<a href="semaphore_destroy.html"><strong>semaphore_destroy</strong></a>, 75*c54f35caSApple OSS Distributions<a href="semaphore_signal.html"><strong>semaphore_signal</strong></a>, 76*c54f35caSApple OSS Distributions<a href="semaphore_signal_all.html"><strong>semaphore_signal_all</strong></a>, 77*c54f35caSApple OSS Distributions<a href="semaphore_wait.html"><strong>semaphore_wait</strong></a>, 78*c54f35caSApple OSS Distributions<a href="device_get_status.html"><strong>device_get_status</strong></a>. 79