1*1031c584SApple OSS Distributions<h2>semaphore_create</h2> 2*1031c584SApple OSS Distributions<hr> 3*1031c584SApple OSS Distributions<p> 4*1031c584SApple OSS Distributions<strong>Function</strong> - Create a new semaphore. 5*1031c584SApple OSS Distributions<h3>SYNOPSIS</h3> 6*1031c584SApple OSS Distributions<pre> 7*1031c584SApple OSS Distributions<strong>kern_return_t semaphore_create</strong> 8*1031c584SApple OSS Distributions <strong>(task_t</strong> <var>task</var>, 9*1031c584SApple OSS Distributions <strong>semaphore_t</strong> <var>*semaphore</var>, 10*1031c584SApple OSS Distributions <strong>int</strong> <var>policy</var>, 11*1031c584SApple OSS Distributions <strong>int</strong> <var>value</var><strong>);</strong> 12*1031c584SApple OSS Distributions</pre> 13*1031c584SApple OSS Distributions<h3>PARAMETERS</h3> 14*1031c584SApple OSS Distributions<dl> 15*1031c584SApple OSS Distributions<dt> <var>task</var> 16*1031c584SApple OSS Distributions<dd> 17*1031c584SApple OSS Distributions[in task port] The task receiving the send right of the newly created semaphore. 18*1031c584SApple OSS Distributions<p> 19*1031c584SApple OSS Distributions<dt> <var>semaphore</var> 20*1031c584SApple OSS Distributions<dd> 21*1031c584SApple OSS Distributions[out send right] The port naming the created semaphore. 22*1031c584SApple OSS Distributions<p> 23*1031c584SApple OSS Distributions<dt> <var>policy</var> 24*1031c584SApple OSS Distributions<dd> 25*1031c584SApple OSS Distributions[in scalar] The blocked thread wakeup policy for the newly created semaphore. Valid policies are: 26*1031c584SApple OSS Distributions<dl> 27*1031c584SApple OSS Distributions<p> 28*1031c584SApple OSS Distributions <dt> SYNC_POLICY_FIFO 29*1031c584SApple OSS Distributions<dd> 30*1031c584SApple OSS Distributionsa first-in-first-out policy for scheduling thread wakeup. 31*1031c584SApple OSS Distributions <p> 32*1031c584SApple OSS Distributions <dt> SYNC_POLICY_FIXED_PRIORITY 33*1031c584SApple OSS Distributions<dd> 34*1031c584SApple OSS Distributionsa fixed priority policy for scheduling thread wakeup. 35*1031c584SApple OSS Distributions </dl> 36*1031c584SApple OSS Distributions <p> 37*1031c584SApple OSS Distributions<dt> <var>value</var> 38*1031c584SApple OSS Distributions<dd> 39*1031c584SApple OSS Distributions[in scalar] The initial value of the semaphore count. 40*1031c584SApple OSS Distributions</dl> 41*1031c584SApple OSS Distributions<h3>DESCRIPTION</h3> 42*1031c584SApple OSS Distributions<p> 43*1031c584SApple OSS DistributionsThe <strong>semaphore_create</strong> function creates a new semaphore, associates the 44*1031c584SApple OSS Distributionscreated semaphore with the specified task, and returns a send right 45*1031c584SApple OSS Distributionsnaming the new semaphore. In order to support a robust 46*1031c584SApple OSS Distributionsproducer/consumer communication service, Interrupt Service Routines 47*1031c584SApple OSS Distributions(ISR) must be able to signal semaphores. The semaphore synchronizer 48*1031c584SApple OSS Distributionsservice is designed to allow user-level device drivers to perform 49*1031c584SApple OSS Distributionssignal operations, eliminating the need for event counters. Device 50*1031c584SApple OSS Distributionsdrivers which utilize semaphores are responsible for creating (via 51*1031c584SApple OSS Distributions<strong>semaphore_create</strong>) and exporting (via <strong>device_get_status</strong>) 52*1031c584SApple OSS Distributionssemaphores for 53*1031c584SApple OSS Distributionsuser level access. Device driver semaphore creation is done at device 54*1031c584SApple OSS Distributionsinitialization time. Device drivers may support multiple semaphores. 55*1031c584SApple OSS Distributions<h3>RETURN VALUES</h3> 56*1031c584SApple OSS Distributions<dl> 57*1031c584SApple OSS Distributions <p> 58*1031c584SApple OSS Distributions<dt> <strong>KERN_INVALID_ARGUMENT</strong> 59*1031c584SApple OSS Distributions<dd> 60*1031c584SApple OSS DistributionsThe task argument or the policy argument was invalid, 61*1031c584SApple OSS Distributions or the initial value of the semaphore was invalid. 62*1031c584SApple OSS Distributions <p> 63*1031c584SApple OSS Distributions<dt> <strong>KERN_RESOURCE_SHORTAGE</strong> 64*1031c584SApple OSS Distributions<dd> 65*1031c584SApple OSS DistributionsThe kernel could not allocate the semaphore. 66*1031c584SApple OSS Distributions <p> 67*1031c584SApple OSS Distributions<dt> <strong>KERN_SUCCESS</strong> 68*1031c584SApple OSS Distributions<dd> 69*1031c584SApple OSS DistributionsThe semaphore was successfully created. 70*1031c584SApple OSS Distributions</dl> 71*1031c584SApple OSS Distributions<h3>RELATED INFORMATION</h3> 72*1031c584SApple OSS Distributions<p> 73*1031c584SApple OSS DistributionsFunctions: 74*1031c584SApple OSS Distributions<a href="semaphore_destroy.html"><strong>semaphore_destroy</strong></a>, 75*1031c584SApple OSS Distributions<a href="semaphore_signal.html"><strong>semaphore_signal</strong></a>, 76*1031c584SApple OSS Distributions<a href="semaphore_signal_all.html"><strong>semaphore_signal_all</strong></a>, 77*1031c584SApple OSS Distributions<a href="semaphore_wait.html"><strong>semaphore_wait</strong></a>, 78*1031c584SApple OSS Distributions<a href="device_get_status.html"><strong>device_get_status</strong></a>. 79