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Diffstat (limited to 'man3/pthread_mutex_init.3')
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diff --git a/man3/pthread_mutex_init.3 b/man3/pthread_mutex_init.3 deleted file mode 100644 index 8d9abf9..0000000 --- a/man3/pthread_mutex_init.3 +++ /dev/null @@ -1,241 +0,0 @@ -.\" Copyright, Xavier Leroy <Xavier.Leroy@inria.fr> -.\" Copyright 2023, Alejandro Colomar <alx@kernel.org> -.\" -.\" SPDX-License-Identifier: Linux-man-pages-copyleft -.\" -.TH pthread_mutex_init 3 2024-02-26 "Linux man-pages 6.7" -. -. -.SH NAME -pthread_mutex_init, -pthread_mutex_lock, -pthread_mutex_trylock, -pthread_mutex_unlock, -pthread_mutex_destroy -\- -operations on mutexes -. -. -.SH SYNOPSIS -.B #include <pthread.h> -.P -.BI "pthread_mutex_t " fastmutex " = PTHREAD_MUTEX_INITIALIZER;" -.BI "pthread_mutex_t " recmutex " = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;" -.BI "pthread_mutex_t " errchkmutex " = PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP;" -.P -.BI "int pthread_mutex_init(pthread_mutex_t *" mutex ", const pthread_mutexattr_t *" mutexattr ");" -.BI "int pthread_mutex_lock(pthread_mutex_t *" mutex ");" -.BI "int pthread_mutex_trylock(pthread_mutex_t *" mutex ");" -.BI "int pthread_mutex_unlock(pthread_mutex_t *" mutex ");" -.BI "int pthread_mutex_destroy(pthread_mutex_t *" mutex ");" -. -. -.SH DESCRIPTION -A mutex is a MUTual EXclusion device, -and is useful for -protecting shared data structures from concurrent modifications, -and implementing critical sections and monitors. -.P -A mutex has two possible states: -unlocked (not owned by any thread), -and locked (owned by one thread). -A mutex can never be owned by two different threads simultaneously. -A thread attempting to lock a mutex -that is already locked by another thread -is suspended until the owning thread unlocks the mutex first. -.P -\fBpthread_mutex_init\fP initializes the mutex object pointed to by \fImutex\fP -according to the mutex attributes specified in \fImutexattr\fP. -If \fImutexattr\fP is \fBNULL\fP, -default attributes are used instead. -.P -The LinuxThreads implementation supports only one mutex attributes, -the \fImutex kind\fP, -which is either ``fast'', -``recursive'', -or ``error checking''. -The kind of a mutex determines -whether it can be locked again by a thread that already owns it. -The default kind is ``fast''. -See \fBpthread_mutexattr_init\fP(3) for more information on mutex attributes. -.P -Variables of type \fBpthread_mutex_t\fP can also be initialized statically, -using the constants -\fBPTHREAD_MUTEX_INITIALIZER\fP -(for fast mutexes), -\fBPTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP\fP -(for recursive mutexes), -and \fBPTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP\fP -(for error checking mutexes). -.P -\fBpthread_mutex_lock\fP locks the given mutex. -If the mutex is currently unlocked, -it becomes locked and owned by the calling thread, -and \fBpthread_mutex_lock\fP returns immediately. -If the mutex is already locked by another thread, -\fBpthread_mutex_lock\fP suspends the calling thread -until the mutex is unlocked. -.P -If the mutex is already locked by the calling thread, -the behavior of \fBpthread_mutex_lock\fP depends on the kind of the mutex. -If the mutex is of the ``fast'' kind, -the calling thread is suspended until the mutex is unlocked, -thus effectively causing the calling thread to deadlock. -If the mutex is of the ``error checking'' kind, -\fBpthread_mutex_lock\fP returns immediately with the error code \fBEDEADLK\fP. -If the mutex is of the ``recursive'' kind, -\fBpthread_mutex_lock\fP succeeds and returns immediately, -recording the number of times the calling thread has locked the mutex. -An equal number of \fBpthread_mutex_unlock\fP operations -must be performed before the mutex returns to the unlocked state. -.P -\fBpthread_mutex_trylock\fP behaves identically to \fBpthread_mutex_lock\fP, -except that it does not block the calling thread -if the mutex is already locked by another thread -(or by the calling thread in the case of a ``fast'' mutex). -Instead, -\fBpthread_mutex_trylock\fP returns immediately -with the error code \fBEBUSY\fP. -.P -\fBpthread_mutex_unlock\fP unlocks the given mutex. -The mutex is assumed to be locked and owned by the calling thread -on entrance to \fBpthread_mutex_unlock\fP. -If the mutex is of the ``fast'' kind, -\fBpthread_mutex_unlock\fP always returns it to the unlocked state. -If it is of the ``recursive'' kind, -it decrements the locking count of the mutex -(number of \fBpthread_mutex_lock\fP operations -performed on it by the calling thread), -and only when this count reaches zero is the mutex actually unlocked. -.P -On ``error checking'' and ``recursive'' mutexes, -\fBpthread_mutex_unlock\fP actually checks at run-time -that the mutex is locked on entrance, -and that it was locked by the same thread -that is now calling \fBpthread_mutex_unlock\fP. -If these conditions are not met, -an error code is returned and the mutex remains unchanged. -``Fast'' mutexes perform no such checks, -thus allowing a locked mutex to be -unlocked by a thread other than its owner. -This is non-portable behavior and must not be relied upon. -.P -\fBpthread_mutex_destroy\fP destroys a mutex object, -freeing the resources it might hold. -The mutex must be unlocked on entrance. -In the LinuxThreads implementation, -no resources are associated with mutex objects, -thus \fBpthread_mutex_destroy\fP actually does nothing -except checking that the mutex is unlocked. -. -. -.SH CANCELLATION -None of the mutex functions is a cancelation point, -not even \fBpthread_mutex_lock\fP, -in spite of the fact that it can suspend a thread for arbitrary durations. -This way, -the status of mutexes at cancelation points is predictable, -allowing cancelation handlers -to unlock precisely those mutexes that need to be unlocked -before the thread stops executing. -Consequently, -threads using deferred cancelation -should never hold a mutex for extended periods of time. -. -. -.SH "ASYNC-SIGNAL SAFETY" -The mutex functions are not async-signal safe. -What this means is that they should not be called from a signal handler. -In particular, -calling \fBpthread_mutex_lock\fP or \fBpthread_mutex_unlock\fP -from a signal handler -may deadlock the calling thread. -. -. -.SH "RETURN VALUE" -\fBpthread_mutex_init\fP always returns 0. -The other mutex functions -return 0 on success and a non-zero error code on error. -. -. -.SH ERRORS -The \fBpthread_mutex_lock\fP function returns -the following error code on error: -.RS -.TP -\fBEINVAL\fP -The mutex has not been properly initialized. -.TP -\fBEDEADLK\fP -The mutex is already locked by the calling thread -(``error checking'' mutexes only). -.RE -.P -The \fBpthread_mutex_trylock\fP function returns -the following error codes on error: -.RS -.TP -\fBEBUSY\fP -The mutex could not be acquired because it was currently locked. -.TP -\fBEINVAL\fP -The mutex has not been properly initialized. -.RE -.P -The \fBpthread_mutex_unlock\fP function returns -the following error code on error: -.RS -.TP -\fBEINVAL\fP -The mutex has not been properly initialized. -.TP -\fBEPERM\fP -The calling thread does not own the mutex -(``error checking'' mutexes only). -.RE -.P -The \fBpthread_mutex_destroy\fP function returns -the following error code on error: -.RS -.TP -\fBEBUSY\fP -The mutex is currently locked. -.RE -. -. -.SH "SEE ALSO" -\fBpthread_mutexattr_init\fP(3), -\fBpthread_mutexattr_setkind_np\fP(3), -\fBpthread_cancel\fP(3). -. -. -.SH EXAMPLE -A shared global variable \fIx\fP can be protected by a mutex as follows: -.P -.RS -.ft 3 -.nf -.sp -int x; -pthread_mutex_t mut = PTHREAD_MUTEX_INITIALIZER; -.ft -.P -.RE -.fi -.P -All accesses and modifications to \fIx\fP -should be bracketed by calls to -\fBpthread_mutex_lock\fP and \fBpthread_mutex_unlock\fP -as follows: -.P -.RS -.ft 3 -.nf -.sp -pthread_mutex_lock(&mut); -/* operate on x */ -pthread_mutex_unlock(&mut); -.ft -.P -.RE -.fi |