44 lines
2.5 KiB
XML
44 lines
2.5 KiB
XML
<?xml version="1.0" encoding="UTF-8" ?>
|
|
<class name="Mutex" inherits="Reference" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../class.xsd">
|
|
<brief_description>
|
|
A synchronization mutex (mutual exclusion).
|
|
</brief_description>
|
|
<description>
|
|
A synchronization mutex (mutual exclusion). This is used to synchronize multiple [Thread]s, and is equivalent to a binary [Semaphore]. It guarantees that only one thread can ever acquire the lock at a time. A mutex can be used to protect a critical section; however, be careful to avoid deadlocks.
|
|
It's of the recursive kind, so it can be locked multiple times by one thread, provided it also unlocks it as many times.
|
|
[b]Warning:[/b]
|
|
To guarantee that the operating system is able to perform proper cleanup (no crashes, no deadlocks), these conditions must be met:
|
|
- By the time a [Mutex]'s reference count reaches zero and therefore it is destroyed, no threads (including the one on which the destruction will happen) must have it locked.
|
|
- By the time a [Thread]'s reference count reaches zero and therefore it is destroyed, it must not have any mutex locked.
|
|
</description>
|
|
<tutorials>
|
|
<link>$DOCS_URL/tutorials/performance/threads/using_multiple_threads.html</link>
|
|
</tutorials>
|
|
<methods>
|
|
<method name="lock">
|
|
<return type="void" />
|
|
<description>
|
|
Locks this [Mutex], blocks until it is unlocked by the current owner.
|
|
[b]Note:[/b] This function returns without blocking if the thread already has ownership of the mutex.
|
|
</description>
|
|
</method>
|
|
<method name="try_lock">
|
|
<return type="int" enum="Error" />
|
|
<description>
|
|
Tries locking this [Mutex], but does not block. Returns [constant OK] on success, [constant ERR_BUSY] otherwise.
|
|
[b]Note:[/b] This function returns [constant OK] if the thread already has ownership of the mutex.
|
|
</description>
|
|
</method>
|
|
<method name="unlock">
|
|
<return type="void" />
|
|
<description>
|
|
Unlocks this [Mutex], leaving it to other threads.
|
|
[b]Note:[/b] If a thread called [method lock] or [method try_lock] multiple times while already having ownership of the mutex, it must also call [method unlock] the same number of times in order to unlock it correctly.
|
|
[b]Warning:[/b] Calling [method unlock] more times that [method lock] on a given thread, thus ending up trying to unlock a non-locked mutex, is wrong and may causes crashes or deadlocks.
|
|
</description>
|
|
</method>
|
|
</methods>
|
|
<constants>
|
|
</constants>
|
|
</class>
|