diff options
Diffstat (limited to 'src/corelib/doc/src/threads.qdoc')
| -rw-r--r-- | src/corelib/doc/src/threads.qdoc | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/src/corelib/doc/src/threads.qdoc b/src/corelib/doc/src/threads.qdoc index d8592bbf09..2726ea1709 100644 --- a/src/corelib/doc/src/threads.qdoc +++ b/src/corelib/doc/src/threads.qdoc @@ -338,6 +338,30 @@ aligned pointers. For instance, you cannot use packed classes with MSVC. + These synchronization classes can be used to make a method thread safe. + However, doing so incurs a performance penalty, which is why most Qt methods + are not made thread safe. + + \section2 Risks + + If a thread locks a resource but does not unlock it, the application may + freeze because the resource will become permanently unavailable to other threads. + This can happen, for example, if a an exception is thrown and forces the current + function to return without releasing its lock. + + Another similar scenario is a \e{deadlock}. For example, suppose that + thread A is waiting for thread B to unlock a resource. If thread B is also + waiting for thread A to unlock a different resource, then both threads will + end up waiting forever, so the application will freeze. + + \section2 Convenience classes + + QMutexLocker, QReadLocker and QWriteLocker are convenience classes that make it + easier to use QMutex and QReadWriteLock. They lock a resource when they are + constructed, and automatically unlock it when they are destroyed. They are + designed to simplify code that use QMutex and QReadWriteLocker, thus reducing + the chances that a resource becomes permanently locked by accident. + \section1 High-Level Event Queues Qt's \l{The Event System}{event system} is very useful for inter-thread |