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author | Ulrich Drepper <drepper@redhat.com> | 1998-03-11 12:42:25 +0000 |
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committer | Ulrich Drepper <drepper@redhat.com> | 1998-03-11 12:42:25 +0000 |
commit | 5afdca0087dad2994ad4fcdfe7f489f4dbcab7b3 (patch) | |
tree | c9c82db2ff92537b921361a02a284b0e18a594b8 /linuxthreads/man/pthread_mutex_init.man | |
parent | 3d76e7784700c20fc222920b2a22baba006daa15 (diff) | |
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LinuxThreads library.
1998-03-11 00:42 Wolfram Gloger <wmglo@dent.med.uni-muenchen.de>
* linuxthreads/manager.c: Enable resetting of the thread
scheduling policy to SCHED_OTHER when the parent thread
has a different one.
1998-02-01 13:51 Ulrich Drepper <drepper@cygnus.com>
* sysdeps/unix/sysv/linux/bits/posix_opt.h: Define
_POSIX_ASYNCHRONOUS_IO.
* sysdeps/pthread/pthread.h: Define bits for Unix98 variants of
mutexes.
* mutex.c: Implement new mutex types.
* internals.h: Include <signal.h>.
* libpthread.map: Add __erno_location and __h_errno_location.
* errno.c: Return pointer to variable actually in use. This might
not be the one in the thread structure.
* internals.h (struct _pthread_descr_struct): Add new fields p_errnop
and p_h_errnop.
* manager.c (__pthread_manager): Set p_errnop and p_h_errnop member
of manager thread structure.
(pthread_handle_create): Set p_errnop and p_h_errnop members for new
thread.
* pthread.c: Adapt initializer for thread structures.
(__pthread_initial_thread): Set p_errnop and p_h_errnop member.
(__pthread_reset_main_thread): Reset p_errnop and p_h_errnop of
current thread to global variables.
1998-01-31 17:27 Ulrich Drepper <drepper@cygnus.com>
* rwlock.c: New file.
* Makefile (libpthread-routines): Add rwlock.
* sysdeps/pthread/pthread.h: Define data structures and declare
functions.
* libpthread.map: Add new functions.
1997-12-18 13:50 Philip Blundell <pb@nexus.co.uk>
* sysdeps/arm/pt-machine.h: New file; add ARM support.
* sysdeps/arm/Implies: likewise.
* README: Document it.
1997-12-13 Andreas Schwab <schwab@issan.informatik.uni-dortmund.de>
* signals.c: Remove unneeded initializer for sigwaited, saving a
1997-04-11 01:18 Andreas Schwab <schwab@issan.informatik.uni-dortmund.de>
* semaphore.c (sem_init): Set sem_spinlock only if available.
1997-12-04 01:48 Ulrich Drepper <drepper@cygnus.com>
* mutex.c: Implement PTHREAD_MUTEX_CHECKERROR.
* sysdeps/pthread/pthread.h: Define PTHREAD_MUTEX_CHECKERROR.
* Makefile: Update from LinuxThreads 0.7.
* internals.h. Likewise.
* manager.c: Likewise.
* mutex.c: Likewise.
* pthread.c: Likewise.
* signals.c: Likewise.
* specific.c: Likewise.
* Examples/ex3.c: Likewise.
1997-11-20 18:13 Ulrich Drepper <drepper@cygnus.com>
* pthread.c (__pthread_reset_main_thread): Close pipe only if still
open.
1997-10-29 05:38 Ulrich Drepper <drepper@cygnus.com>
* wrapsyscall.c: Add socket functions which are also cancelation
points.
1997-10-19 21:40 Wolfram Gloger <wg@wolfram.dent.med.uni-muenchen.de>
* specific.c (__libc_internal_tsd_set, __libc_internal_tsd_get):
New functions for fast thread specific data within libc.
* internals.h: Add new array p_libc_specific to struct
_pthread_descr_struct.
* sysdeps/pthread/bits/libc-lock.h: Declare new functions.
1997-10-13 05:39 Ulrich Drepper <drepper@cygnus.com>
* semaphore.h: Add __BEGIN_DECLS/__END_DECLS.
Reported by Ralf Corsepius <corsepiu@faw.uni-ulm.de>.
1997-08-29 03:05 Ulrich Drepper <drepper@cygnus.com>
* internals.h (struct _pthread_descr_struct): Add definitions for
two-level specific key handling.
* manager.c (pthread_handle_create): Initialize specific memory array.
* specific.c: Implement two-level key handling.
* weaks.c: Don't provide dummy key handling.
* sysdeps/pthread/bits/libc-lock.h: Typedef __libc_lock_t (no #define).
Add definition of __libc_key_t.
* sysdeps/unix/sysv/linux/bits/local_lim.h: Define PTHREAD_KEYS_MAX
as 1024.
Add definition of _POSIX_THREAD_DESTRUCTOR_ITERATIONS and
PTHREAD_DESTRUCTOR_ITERATIONS.
* manager.c (pthread_handle_create): Compare mmap result with
MAP_FAILED.
* ptfork.c: Rename to __pthread_atfork and make old name a weak alias.
* sysdeps/pthread/bits/pthread.h: Add prototype for __pthread_atfork.
1997-08-22 19:04 Richard Henderson <rth@cygnus.com>
sysdeps/sparc -> sysdeps/sparc/sparc32
sysdeps/sparc64 -> sysdeps/sparc/sparc64
* internals.h: Change definition of THREAD_SELF to be an expression,
not a statement that did a return.
* sysdeps/alpha/pt-machine.h (THREAD_SELF): Update accordingly.
* sysdeps/sparc/sparc32/pt-machine.h (THREAD_SELF, INIT_THREAD_SELF):
Follow Solaris and use a "system reserved" register (%g6) to hold
the thread descriptor.
* sysdeps/sparc/sparc64/pt-machine.h: Likewise.
1997-08-03 00:09 Ulrich Drepper <drepper@cygnus.com>
* mutex.c: Correct pthread_once. Patch by Xavier Leroy.
* sysdeps/pthread/pthread.h: Add prototype for __pthread_once.
* sysdeps/pthread/bits/pthread.h: Add macros for __libc_once.
* semaphore.c: Include spinlock.h only when needed.
* specific.c (__pthread_setsepcific, __pthread_getspecific): Reject
keys for entries not in use.
* weaks.c: Implement key handling functions for real.
1997-06-29 01:04 Richard Henderson <richard@gnu.ai.mit.edu>
Initial sparc64-linux support:
* linuxthreads/sysdeps/sparc64/Implies: New file.
* linuxthreads/sysdeps/sparc64/pt-machine.h: Likewise.
1997-06-29 00:48 Ulrich Drepper <drepper@cygnus.com>
* semaphore.c: Include spinlock.h at correct place.
Patch by HJ Lu.
1997-06-13 10:06 Richard Henderson <rth@tamu.edu>
The Great Bit File Move:
* sysdeps/alpha/semaphorebits.h: -> .../bits/semaphore.h.
* sysdeps/powerpc/semaphorebits.h: Likewise.
* sysdeps/pthread/cmpxchg/semaphorebits.h: Likewise.
* sysdeps/pthread/no-cmpxchg/semaphorebits.h: Likewise.
* sysdeps/pthread/libc-lock.h: -> bits/
* sysdeps/pthread/stdio-lock.h: Likewise.
* sysdeps/unix/sysv/linux/local_lim.h: Likewise.
* sysdeps/unix/sysv/linux/posix_opt.h: Likewise.
* semaphore.h: Likewise.
* sysdeps/pthread/pthread.h: Likewise.
* lockfile.c: <foo.h> -> <bits/foo.h>.
* semaphore.h: Likewise.
* Makefile: (headers): foo.h -> bits/foo.h.
* sysdeps/pthread/Makefile: Likewise.
1997-04-11 01:18 Andreas Schwab <schwab@issan.informatik.uni-dortmund.de>
* semaphore.c (sem_init): Set sem_spinlock only if available.
* sysdeps/m68k/pt-machine.h (testandset, __compare_and_swap): Fix
asm constraints.
1997-04-09 03:00 Ulrich Drepper <drepper@cygnus.com>
Update from LinuxThreads 0.6.
* attr.c (pthread_attr_getdetachstate): Use __sched_get_priority_max
and __sched_get_priority_min instead of names without `__'.
* manager.c: Rewrite large parts to implement opaque pthread_t.
* cancel.c: Adapt for opaque pthread_t type.
* condvar.c: Likewise.
* errno.c: Likewise.
* join.c: Likewise.
* mutex.c: Likewise.
* pthread.c: Likewise.
* signals.c: Likewise.
* specific.c: Likewise.
* restart.h: Likewise.
* queue.h: Likewise.
* Examples/ex3.c: Likewise.
* Examples/ex4.c: Likewise.
* sysdeps/pthread/pthread.h: Likewise.
* pthread.c: Accumulate time for all threads in thread manager.
* semaphore.c: Implement fallback implementation for architectures
sometimes missing compare-exchange operations.
* cancel.c (pthread_cancel): Validate handle argument.
* join.c (pthread_join): Likewise.
(pthread_detach): Likewise.
* signals.c (pthread_kill): Likewise.
* spinlock.h (acquire): Use __sched_yield not sched_yield.
* queue.h (enqueue): Enqueue thread according to priority.
* internals.c (struct pthread_start_args): New struct for passing
args to cloning function.
(struct _pthread): Rename to _pthread_descr_struct and adapt for
opaque pthread_t.
* Examples/Makefile (clean): Pass -f option to rm.
* sysdeps/i386/pt-machine.h: Add check for compare-exchange instruction
and define TEST_FOR_COMPARE_AND_SWAP.
* sysdeps/i386/i486/pt-machine.h: Removed.
* sysdeps/unix/sysv/linux/local_lim.h (PTHREAD_THREADS_MAX): Increase
to 1024.
1997-04-04 16:38 Ulrich Drepper <drepper@cygnus.com>
* restart.h (suspend): Clear p_signal before suspending.
(suspend_with_cancellation): Likewise.
Patch by Xavier Leroy <Xavier.Leroy@inria.fr>.
* weaks.c: Make __pthread_key_create return 1.
* sysdeps/pthread/libc-lock.h: Define __libc_key_create,
__libc_getspecific, __libc_setspecific, and __libc_key_t.
* sysdeps/pthread/stdio-lock.h: Don't care for implementation not
using libio.
1997-03-19 15:13 Miguel de Icaza <miguel@nuclecu.unam.mx>
* sysdeps/sparc/pt-machine (RELEASE): Fix.
1997-03-01 07:55 Geoff Keating <geoffk@ozemail.com.au>
* sysdeps/powerpc/Implies: Added.
* sysdeps/powerpc/pt-machine.h: Added.
* sysdeps/powerpc/semaphorebits.h: Added.
1997-01-22 01:22 Ulrich Drepper <drepper@cygnus.com>
* linuxtheads/pthread.c (__pthread_initial_thread): Correct
initializer.
(__pthread_manager_thread): Likewise.
Reported by Andreas Jaeger.
1997-01-18 22:15 Richard Henderson <rth@tamu.edu>
Since sigset_t no longer fits in a register, we can't pass in the
thread's initial mask so easily. Take this opportunity to simplify
the clone implementation by only accepting a single void* argument.
* linuxthreads/manager.c (__pthread_manager): Put thread vitals
in the thread struct instead of as arguments through clone.
(pthread_start_thread): Look for them there.
* linuxthreads/internals.h (struct _pthread): Add p_initial_fn,
p_initial_fn_arg, p_initial_mask. Fix __pthread_manager proto.
* linuxthreads/pthread.c (pthread_initialize_manager): Revise
clone invocation.
Diffstat (limited to 'linuxthreads/man/pthread_mutex_init.man')
-rw-r--r-- | linuxthreads/man/pthread_mutex_init.man | 213 |
1 files changed, 213 insertions, 0 deletions
diff --git a/linuxthreads/man/pthread_mutex_init.man b/linuxthreads/man/pthread_mutex_init.man new file mode 100644 index 0000000000..bda4ec6c4d --- /dev/null +++ b/linuxthreads/man/pthread_mutex_init.man @@ -0,0 +1,213 @@ +.TH PTHREAD_MUTEX 3 LinuxThreads + +.XREF pthread_mutex_lock +.XREF pthread_mutex_unlock +.XREF pthread_mutex_trylock +.XREF pthread_mutex_destroy + +.SH NAME +pthread_mutex_init, pthread_mutex_lock, pthread_mutex_trylock, pthread_mutex_unlock, pthread_mutex_destroy \- operations on mutexes + +.SH SYNOPSIS +#include <pthread.h> + +pthread_mutex_t fastmutex = PTHREAD_MUTEX_INITIALIZER; + +pthread_mutex_t recmutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP; + +pthread_mutex_t errchkmutex = PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP; + +int pthread_mutex_init(pthread_mutex_t *mutex, const pthread_mutexattr_t *mutexattr); + +int pthread_mutex_lock(pthread_mutex_t *mutex)); + +int pthread_mutex_trylock(pthread_mutex_t *mutex); + +int pthread_mutex_unlock(pthread_mutex_t *mutex); + +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. + +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. + +!pthread_mutex_init! initializes the mutex object pointed to by +|mutex| according to the mutex attributes specified in |mutexattr|. +If |mutexattr| is !NULL!, default attributes are used instead. + +The LinuxThreads implementation supports only one mutex attributes, +the |mutex kind|, 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 !pthread_mutexattr_init!(3) for more +information on mutex attributes. + +Variables of type !pthread_mutex_t! can also be initialized +statically, using the constants !PTHREAD_MUTEX_INITIALIZER! (for fast +mutexes), !PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP! (for recursive +mutexes), and !PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP! (for error checking +mutexes). + +!pthread_mutex_lock! locks the given mutex. If the mutex is currently +unlocked, it becomes locked and owned by the calling thread, and +!pthread_mutex_lock! returns immediately. If the mutex is already +locked by another thread, !pthread_mutex_lock! suspends the calling +thread until the mutex is unlocked. + +If the mutex is already locked by the calling thread, the behavior of +!pthread_mutex_lock! 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, +!pthread_mutex_lock! returns immediately with the error code !EDEADLK!. +If the mutex is of the ``recursive'' kind, !pthread_mutex_lock! +succeeds and returns immediately, recording the number of times the +calling thread has locked the mutex. An equal number of +!pthread_mutex_unlock! operations must be performed before the mutex +returns to the unlocked state. + +!pthread_mutex_trylock! behaves identically to !pthread_mutex_lock!, +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, !pthread_mutex_trylock! returns +immediately with the error code !EBUSY!. + +!pthread_mutex_unlock! unlocks the given mutex. The mutex is assumed +to be locked and owned by the calling thread on entrance to +!pthread_mutex_unlock!. If the mutex is of the ``fast'' kind, +!pthread_mutex_unlock! always returns it to the unlocked state. If it +is of the ``recursive'' kind, it decrements the locking count of the +mutex (number of !pthread_mutex_lock! operations performed on it by +the calling thread), and only when this count reaches zero is the +mutex actually unlocked. + +On ``error checking'' mutexes, !pthread_mutex_unlock! 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 !pthread_mutex_unlock!. +If these conditions are not met, an error code is returned and the +mutex remains unchanged. ``Fast'' and ``recursive'' 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. + +!pthread_mutex_destroy! 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 !pthread_mutex_destroy! actually does nothing except +checking that the mutex is unlocked. + +.SH CANCELLATION + +None of the mutex functions is a cancellation point, not even +!pthread_mutex_lock!, in spite of the fact that it can suspend a +thread for arbitrary durations. This way, the status of mutexes at +cancellation points is predictable, allowing cancellation handlers to +unlock precisely those mutexes that need to be unlocked before the +thread stops executing. Consequently, threads using deferred +cancellation 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 !pthread_mutex_lock! or !pthread_mutex_unlock! from a signal +handler may deadlock the calling thread. + +.SH "RETURN VALUE" + +!pthread_mutex_init! always returns 0. The other mutex functions +return 0 on success and a non-zero error code on error. + +.SH ERRORS + +The !pthread_mutex_lock! function returns the following error code +on error: +.RS +.TP +!EINVAL! +the mutex has not been properly initialized. + +.TP +!EDEADLK! +the mutex is already locked by the calling thread +(``error checking'' mutexes only). +.RE + +The !pthread_mutex_trylock! function returns the following error codes +on error: +.RS +.TP +!EBUSY! +the mutex could not be acquired because it was currently locked. + +.TP +!EINVAL! +the mutex has not been properly initialized. +.RE + +The !pthread_mutex_unlock! function returns the following error code +on error: +.RS +.TP +!EINVAL! +the mutex has not been properly initialized. + +.TP +!EPERM! +the calling thread does not own the mutex (``error checking'' mutexes only). +.RE + +The !pthread_mutex_destroy! function returns the following error code +on error: +.RS +.TP +!EBUSY! +the mutex is currently locked. +.RE + +.SH AUTHOR +Xavier Leroy <Xavier.Leroy@inria.fr> + +.SH "SEE ALSO" +!pthread_mutexattr_init!(3), +!pthread_mutexattr_setkind_np!(3), +!pthread_cancel!(3). + +.SH EXAMPLE + +A shared global variable |x| can be protected by a mutex as follows: + +.RS +.ft 3 +.nf +.sp +int x; +pthread_mutex_t mut = PTHREAD_MUTEX_INITIALIZER; +.ft +.LP +.RE +.fi + +All accesses and modifications to |x| should be bracketed by calls to +!pthread_mutex_lock! and !pthread_mutex_unlock! as follows: + +.RS +.ft 3 +.nf +.sp +pthread_mutex_lock(&mut); +/* operate on x */ +pthread_mutex_unlock(&mut); +.ft +.LP +.RE +.fi + + |