1*0f4c859eSApple OSS Distributions<h2>semaphore_create</h2> 2*0f4c859eSApple OSS Distributions<hr> 3*0f4c859eSApple OSS Distributions<p> 4*0f4c859eSApple OSS Distributions<strong>Function</strong> - Create a new semaphore. 5*0f4c859eSApple OSS Distributions<h3>SYNOPSIS</h3> 6*0f4c859eSApple OSS Distributions<pre> 7*0f4c859eSApple OSS Distributions<strong>kern_return_t semaphore_create</strong> 8*0f4c859eSApple OSS Distributions <strong>(task_t</strong> <var>task</var>, 9*0f4c859eSApple OSS Distributions <strong>semaphore_t</strong> <var>*semaphore</var>, 10*0f4c859eSApple OSS Distributions <strong>int</strong> <var>policy</var>, 11*0f4c859eSApple OSS Distributions <strong>int</strong> <var>value</var><strong>);</strong> 12*0f4c859eSApple OSS Distributions</pre> 13*0f4c859eSApple OSS Distributions<h3>PARAMETERS</h3> 14*0f4c859eSApple OSS Distributions<dl> 15*0f4c859eSApple OSS Distributions<dt> <var>task</var> 16*0f4c859eSApple OSS Distributions<dd> 17*0f4c859eSApple OSS Distributions[in task port] The task receiving the send right of the newly created semaphore. 18*0f4c859eSApple OSS Distributions<p> 19*0f4c859eSApple OSS Distributions<dt> <var>semaphore</var> 20*0f4c859eSApple OSS Distributions<dd> 21*0f4c859eSApple OSS Distributions[out send right] The port naming the created semaphore. 22*0f4c859eSApple OSS Distributions<p> 23*0f4c859eSApple OSS Distributions<dt> <var>policy</var> 24*0f4c859eSApple OSS Distributions<dd> 25*0f4c859eSApple OSS Distributions[in scalar] The blocked thread wakeup policy for the newly created semaphore. Valid policies are: 26*0f4c859eSApple OSS Distributions<dl> 27*0f4c859eSApple OSS Distributions<p> 28*0f4c859eSApple OSS Distributions <dt> SYNC_POLICY_FIFO 29*0f4c859eSApple OSS Distributions<dd> 30*0f4c859eSApple OSS Distributionsa first-in-first-out policy for scheduling thread wakeup. 31*0f4c859eSApple OSS Distributions <p> 32*0f4c859eSApple OSS Distributions <dt> SYNC_POLICY_FIXED_PRIORITY 33*0f4c859eSApple OSS Distributions<dd> 34*0f4c859eSApple OSS Distributionsa fixed priority policy for scheduling thread wakeup. 35*0f4c859eSApple OSS Distributions </dl> 36*0f4c859eSApple OSS Distributions <p> 37*0f4c859eSApple OSS Distributions<dt> <var>value</var> 38*0f4c859eSApple OSS Distributions<dd> 39*0f4c859eSApple OSS Distributions[in scalar] The initial value of the semaphore count. 40*0f4c859eSApple OSS Distributions</dl> 41*0f4c859eSApple OSS Distributions<h3>DESCRIPTION</h3> 42*0f4c859eSApple OSS Distributions<p> 43*0f4c859eSApple OSS DistributionsThe <strong>semaphore_create</strong> function creates a new semaphore, associates the 44*0f4c859eSApple OSS Distributionscreated semaphore with the specified task, and returns a send right 45*0f4c859eSApple OSS Distributionsnaming the new semaphore. In order to support a robust 46*0f4c859eSApple OSS Distributionsproducer/consumer communication service, Interrupt Service Routines 47*0f4c859eSApple OSS Distributions(ISR) must be able to signal semaphores. The semaphore synchronizer 48*0f4c859eSApple OSS Distributionsservice is designed to allow user-level device drivers to perform 49*0f4c859eSApple OSS Distributionssignal operations, eliminating the need for event counters. Device 50*0f4c859eSApple OSS Distributionsdrivers which utilize semaphores are responsible for creating (via 51*0f4c859eSApple OSS Distributions<strong>semaphore_create</strong>) and exporting (via <strong>device_get_status</strong>) 52*0f4c859eSApple OSS Distributionssemaphores for 53*0f4c859eSApple OSS Distributionsuser level access. Device driver semaphore creation is done at device 54*0f4c859eSApple OSS Distributionsinitialization time. Device drivers may support multiple semaphores. 55*0f4c859eSApple OSS Distributions<h3>RETURN VALUES</h3> 56*0f4c859eSApple OSS Distributions<dl> 57*0f4c859eSApple OSS Distributions <p> 58*0f4c859eSApple OSS Distributions<dt> <strong>KERN_INVALID_ARGUMENT</strong> 59*0f4c859eSApple OSS Distributions<dd> 60*0f4c859eSApple OSS DistributionsThe task argument or the policy argument was invalid, 61*0f4c859eSApple OSS Distributions or the initial value of the semaphore was invalid. 62*0f4c859eSApple OSS Distributions <p> 63*0f4c859eSApple OSS Distributions<dt> <strong>KERN_RESOURCE_SHORTAGE</strong> 64*0f4c859eSApple OSS Distributions<dd> 65*0f4c859eSApple OSS DistributionsThe kernel could not allocate the semaphore. 66*0f4c859eSApple OSS Distributions <p> 67*0f4c859eSApple OSS Distributions<dt> <strong>KERN_SUCCESS</strong> 68*0f4c859eSApple OSS Distributions<dd> 69*0f4c859eSApple OSS DistributionsThe semaphore was successfully created. 70*0f4c859eSApple OSS Distributions</dl> 71*0f4c859eSApple OSS Distributions<h3>RELATED INFORMATION</h3> 72*0f4c859eSApple OSS Distributions<p> 73*0f4c859eSApple OSS DistributionsFunctions: 74*0f4c859eSApple OSS Distributions<a href="semaphore_destroy.html"><strong>semaphore_destroy</strong></a>, 75*0f4c859eSApple OSS Distributions<a href="semaphore_signal.html"><strong>semaphore_signal</strong></a>, 76*0f4c859eSApple OSS Distributions<a href="semaphore_signal_all.html"><strong>semaphore_signal_all</strong></a>, 77*0f4c859eSApple OSS Distributions<a href="semaphore_wait.html"><strong>semaphore_wait</strong></a>, 78*0f4c859eSApple OSS Distributions<a href="device_get_status.html"><strong>device_get_status</strong></a>. 79