projects / apple / xnu.git / blame
| Commit | Line | Data |
|---|---|---|
| 13fec989 A |
1 | <h2>semaphore_create</h2> |
| 2 | <hr> | |
| 3 | <p> | |
| 4 | <strong>Function</strong> - Create a new semaphore. | |
| 5 | <h3>SYNOPSIS</h3> | |
| 6 | <pre> | |
| 7 | <strong>kern_return_t semaphore_create</strong> | |
| 8 | <strong>(task_t</strong> <var>task</var>, | |
| 9 | <strong>semaphore_t</strong> <var>*semaphore</var>, | |
| 10 | <strong>int</strong> <var>policy</var>, | |
| 11 | <strong>int</strong> <var>value</var><strong>);</strong> | |
| 12 | </pre> | |
| 13 | <h3>PARAMETERS</h3> | |
| 14 | <dl> | |
| 15 | <dt> <var>task</var> | |
| 16 | <dd> | |
| 17 | [in task port] The task receiving the send right of the newly created semaphore. | |
| 18 | <p> | |
| 19 | <dt> <var>semaphore</var> | |
| 20 | <dd> | |
| 21 | [out send right] The port naming the created semaphore. | |
| 22 | <p> | |
| 23 | <dt> <var>policy</var> | |
| 24 | <dd> | |
| 25 | [in scalar] The blocked thread wakeup policy for the newly created semaphore. Valid policies are: | |
| 26 | <dl> | |
| 27 | <p> | |
| 28 | <dt> SYNC_POLICY_FIFO | |
| 29 | <dd> | |
| 30 | a first-in-first-out policy for scheduling thread wakeup. | |
| 31 | <p> | |
| 32 | <dt> SYNC_POLICY_FIXED_PRIORITY | |
| 33 | <dd> | |
| 34 | a fixed priority policy for scheduling thread wakeup. | |
| 35 | </dl> | |
| 36 | <p> | |
| 37 | <dt> <var>value</var> | |
| 38 | <dd> | |
| 39 | [in scalar] The initial value of the semaphore count. | |
| 40 | </dl> | |
| 41 | <h3>DESCRIPTION</h3> | |
| 42 | <p> | |
| 43 | The <strong>semaphore_create</strong> function creates a new semaphore, associates the | |
| 44 | created semaphore with the specified task, and returns a send right | |
| 45 | naming the new semaphore. In order to support a robust | |
| 46 | producer/consumer communication service, Interrupt Service Routines | |
| 47 | (ISR) must be able to signal semaphores. The semaphore synchronizer | |
| 48 | service is designed to allow user-level device drivers to perform | |
| 49 | signal operations, eliminating the need for event counters. Device | |
| 50 | drivers which utilize semaphores are responsible for creating (via | |
| 51 | <strong>semaphore_create</strong>) and exporting (via <strong>device_get_status</strong>) | |
| 52 | semaphores for | |
| 53 | user level access. Device driver semaphore creation is done at device | |
| 54 | initialization time. Device drivers may support multiple semaphores. | |
| 55 | <h3>RETURN VALUES</h3> | |
| 56 | <dl> | |
| 57 | <p> | |
| 58 | <dt> <strong>KERN_INVALID_ARGUMENT</strong> | |
| 59 | <dd> | |
| 60 | The task argument or the policy argument was invalid, | |
| 61 | or the initial value of the semaphore was invalid. | |
| 62 | <p> | |
| 63 | <dt> <strong>KERN_RESOURCE_SHORTAGE</strong> | |
| 64 | <dd> | |
| 65 | The kernel could not allocate the semaphore. | |
| 66 | <p> | |
| 67 | <dt> <strong>KERN_SUCCESS</strong> | |
| 68 | <dd> | |
| 69 | The semaphore was successfully created. | |
| 70 | </dl> | |
| 71 | <h3>RELATED INFORMATION</h3> | |
| 72 | <p> | |
| 73 | Functions: | |
| 74 | <a href="semaphore_destroy.html"><strong>semaphore_destroy</strong></a>, | |
| 75 | <a href="semaphore_signal.html"><strong>semaphore_signal</strong></a>, | |
| 76 | <a href="semaphore_signal_all.html"><strong>semaphore_signal_all</strong></a>, | |
| 77 | <a href="semaphore_wait.html"><strong>semaphore_wait</strong></a>, | |
| 78 | <a href="device_get_status.html"><strong>device_get_status</strong></a>. |