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Semaphore¶
Inherits: RefCounted < Object
A synchronization mechanism used to control access to a shared resource by Threads.
描述¶
A synchronization semaphore that can be used to synchronize multiple Threads. Initialized to zero on creation. For a binary version, see Mutex.
Warning: Semaphores must be used carefully to avoid deadlocks.
Warning: To guarantee that the operating system is able to perform proper cleanup (no crashes, no deadlocks), these conditions must be met:
When a Semaphore's reference count reaches zero and it is therefore destroyed, no threads must be waiting on it.
When a Thread's reference count reaches zero and it is therefore destroyed, it must not be waiting on any semaphore.
教程¶
Methods¶
void |
post ( ) |
try_wait ( ) |
|
void |
wait ( ) |
Method Descriptions¶
void post ( )
Lowers the Semaphore, allowing one more thread in.
bool try_wait ( )
Like wait, but won't block, so if the value is zero, fails immediately and returns false. If non-zero, it returns true to report success.
void wait ( )
Waits for the Semaphore, if its value is zero, blocks until non-zero.