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#Join and cancel pthread c software

Often, you want data specific to a particular thread. Le_thread_Join() fetches the return/exit value of the thread that it joined with. This also means that if a thread is joinable, someone must join with it, or its resources will never get cleaned up (until the process terminates). But, a joinable thread doesn't disappear until another thread "joins" with it. Normally, when a thread terminates, it disappears. le_thread_Join(T) blocks the calling thread until thread T exits.įor a thread to be joinable, it must have its "joinable" attribute set (using le_thread_SetJoinable()) prior to being started. Joining is done by a call to le_thread_Join(). Forking is done by creating and starting a thread. Sometimes, you want single execution thread split (fork) into separate threads of parallel execution and later join back together into one thread later. If a cancellation request is made (by calling le_thread_Cancel() or pthread_cancel()), it will be blocked and remain in a pending state until cancellation is unblocked (also using pthread_setcancelstate()), at which time the thread will be immediately cancelled. To prevent cancellation during a critical section (e.g., when a mutex lock is held), pthread_setcancelstate() can be called.

See 'man 7 pthreads' for more information on cancellation and cancellation points. If it is in the middle of doing something that can't be interrupted, it will not terminate until it is finished. See Joining for more information.Ĭanceling a thread may not cause the thread to terminate immediately. If a thread terminates itself, and it is "joinable", it can pass a void* value to another thread that "joins" with it. Threads can also tell other threads to terminate by "canceling" them done through a call to le_thread_Cancel(). No other thread should try to set any attributes of T2 or try to start it.

Warning It is assumed that if a thread T1 creates another thread T2 then only thread T1 will set the attributes and start thread T2. When all attributes have been set, the thread can be started by calling le_thread_Start(). All attributes have default values so it is not necessary to set any attributes (other than the name and main function address, which are passed into le_thread_Create() ). In this state, attributes like scheduling priority and stack size can use the appropriate "Set" functions. Threads are created in a suspended state.

To make it possible to address them by name.

To create a thread, call le_thread_Create(). Some of the most tenacious, intermittent defects known to humankind have resulted from the misuse of multi-threading. In some cases, the workarounds required to avoid multi-threading will cost more memory and/or CPU cycles than using multi-threading would.īut you must be careful with multi-threading. In these cases, it is far better to take advantage of multi-threading to simplify the design, even if it means that the program uses more memory or more CPU cycles.

#Join and cancel pthread c software

Sometimes, this style doesn't fit well with a problem being solved, so you're forced to implement workarounds that severely complicate the software design.

there's no need to use thread synchronization mechanisms, like mutexes, to prevent race conditions between threads.

there's only one copy of thread-specific memory objects, like the procedure call stack.

there's no CPU time spent switching between threads.

With single-threaded, event driven designs: Generally, using single-threaded, event-driven programming (registering callbacks to be called by an event handling loop running in a single thread) is more efficient than using multiple threads.