@node POSIX Threads
@c @node POSIX Threads, Internal Probes, Cryptographic Functions, Top
@chapter POSIX Threads
@c %MENU% POSIX Threads
@cindex pthreads

This chapter describes the @glibcadj{} POSIX Thread implementation.

@menu
* Thread-specific Data::          Support for creating and
				  managing thread-specific data
* Non-POSIX Extensions::          Additional functions to extend
				  POSIX Thread functionality
@end menu

@node Thread-specific Data
@section Thread-specific Data

The @glibcadj{} implements functions to allow users to create and manage
data specific to a thread.  Such data may be destroyed at thread exit,
if a destructor is provided.  The following functions are defined:

@comment pthread.h
@comment POSIX
@deftypefun int pthread_key_create (pthread_key_t *@var{key}, void (*@var{destructor})(void*))
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
@c pthread_key_create ok
@c  KEY_UNUSED ok
@c  KEY_USABLE ok
Create a thread-specific data key for the calling thread, referenced by
@var{key}.

Objects declared with the C++11 @code{thread_local} keyword are destroyed
before thread-specific data, so they should not be used in thread-specific
data destructors or even as members of the thread-specific data, since the
latter is passed as an argument to the destructor function.
@end deftypefun

@comment pthread.h
@comment POSIX
@deftypefun int pthread_key_delete (pthread_key_t @var{key})
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
@c pthread_key_delete ok
@c   This uses atomic compare and exchange to increment the seq number
@c   after testing it's not a KEY_UNUSED seq number.
@c  KEY_UNUSED dup ok
Destroy the thread-specific data @var{key} in the calling thread.  The
destructor for the thread-specific data is not called during destruction, nor
is it called during thread exit.
@end deftypefun

@comment pthread.h
@comment POSIX
@deftypefun void *pthread_getspecific (pthread_key_t @var{key})
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
@c pthread_getspecific ok
Return the thread-specific data associated with @var{key} in the calling
thread.
@end deftypefun

@comment pthread.h
@comment POSIX
@deftypefun int pthread_setspecific (pthread_key_t @var{key}, const void *@var{value})
@safety{@prelim{}@mtsafe{}@asunsafe{@asucorrupt{} @ascuheap{}}@acunsafe{@acucorrupt{} @acsmem{}}}
@c pthread_setspecific @asucorrupt @ascuheap @acucorrupt @acsmem
@c   a level2 block may be allocated by a signal handler after
@c   another call already made a decision to allocate it, thus losing
@c   the allocated value.  the seq number is updated before the
@c   value, which might cause an earlier-generation value to seem
@c   current if setspecific is cancelled or interrupted by a signal
@c  KEY_UNUSED ok
@c  calloc dup @ascuheap @acsmem
Associate the thread-specific @var{value} with @var{key} in the calling thread.
@end deftypefun


@node Non-POSIX Extensions
@section Non-POSIX Extensions

In addition to implementing the POSIX API for threads, @theglibc{} provides
additional functions and interfaces to provide functionality not specified in
the standard.

@menu
* Default Thread Attributes::             Setting default attributes for
					  threads in a process.
@end menu

@node Default Thread Attributes
@subsection Setting Process-wide defaults for thread attributes

@Theglibc{} provides non-standard API functions to set and get the default
attributes used in the creation of threads in a process.

@comment pthread.h
@comment GNU
@deftypefun int pthread_getattr_default_np (pthread_attr_t *@var{attr})
@safety{@prelim{}@mtsafe{}@asunsafe{@asulock{}}@acunsafe{@aculock{}}}
@c Takes lock around read from default_pthread_attr.
Get the default attribute values and set @var{attr} to match.  This
function returns @math{0} on success and a non-zero error code on
failure.
@end deftypefun

@comment pthread.h
@comment GNU
@deftypefun int pthread_setattr_default_np (pthread_attr_t *@var{attr})
@safety{@prelim{}@mtsafe{}@asunsafe{@ascuheap{} @asulock{}}@acunsafe{@aculock{} @acsmem{}}}
@c pthread_setattr_default_np @ascuheap @asulock @aculock @acsmem
@c  check_sched_policy_attr ok
@c  check_sched_priority_attr ok
@c   sched_get_priority_min dup ok
@c   sched_get_priority_max dup ok
@c  check_stacksize_attr ok
@c  lll_lock @asulock @aculock
@c  free dup @ascuheap @acsmem
@c  realloc dup @ascuheap @acsmem
@c  memcpy dup ok
@c  lll_unlock @asulock @aculock
Set the default attribute values to match the values in @var{attr}.  The
function returns @math{0} on success and a non-zero error code on failure.
The following error codes are defined for this function:

@table @code
@item EINVAL
At least one of the values in @var{attr} does not qualify as valid for the
attributes or the stack address is set in the attribute.
@item ENOMEM
The system does not have sufficient memory.
@end table
@end deftypefun

@c FIXME these are undocumented:
@c pthread_atfork
@c pthread_attr_destroy
@c pthread_attr_getaffinity_np
@c pthread_attr_getdetachstate
@c pthread_attr_getguardsize
@c pthread_attr_getinheritsched
@c pthread_attr_getschedparam
@c pthread_attr_getschedpolicy
@c pthread_attr_getscope
@c pthread_attr_getstack
@c pthread_attr_getstackaddr
@c pthread_attr_getstacksize
@c pthread_attr_init
@c pthread_attr_setaffinity_np
@c pthread_attr_setdetachstate
@c pthread_attr_setguardsize
@c pthread_attr_setinheritsched
@c pthread_attr_setschedparam
@c pthread_attr_setschedpolicy
@c pthread_attr_setscope
@c pthread_attr_setstack
@c pthread_attr_setstackaddr
@c pthread_attr_setstacksize
@c pthread_barrierattr_destroy
@c pthread_barrierattr_getpshared
@c pthread_barrierattr_init
@c pthread_barrierattr_setpshared
@c pthread_barrier_destroy
@c pthread_barrier_init
@c pthread_barrier_wait
@c pthread_cancel
@c pthread_cleanup_push
@c pthread_cleanup_pop
@c pthread_condattr_destroy
@c pthread_condattr_getclock
@c pthread_condattr_getpshared
@c pthread_condattr_init
@c pthread_condattr_setclock
@c pthread_condattr_setpshared
@c pthread_cond_broadcast
@c pthread_cond_destroy
@c pthread_cond_init
@c pthread_cond_signal
@c pthread_cond_timedwait
@c pthread_cond_wait
@c pthread_create
@c pthread_detach
@c pthread_equal
@c pthread_exit
@c pthread_getaffinity_np
@c pthread_getattr_np
@c pthread_getconcurrency
@c pthread_getcpuclockid
@c pthread_getname_np
@c pthread_getschedparam
@c pthread_join
@c pthread_kill
@c pthread_kill_other_threads_np
@c pthread_mutexattr_destroy
@c pthread_mutexattr_getkind_np
@c pthread_mutexattr_getprioceiling
@c pthread_mutexattr_getprotocol
@c pthread_mutexattr_getpshared
@c pthread_mutexattr_getrobust
@c pthread_mutexattr_getrobust_np
@c pthread_mutexattr_gettype
@c pthread_mutexattr_init
@c pthread_mutexattr_setkind_np
@c pthread_mutexattr_setprioceiling
@c pthread_mutexattr_setprotocol
@c pthread_mutexattr_setpshared
@c pthread_mutexattr_setrobust
@c pthread_mutexattr_setrobust_np
@c pthread_mutexattr_settype
@c pthread_mutex_consistent
@c pthread_mutex_consistent_np
@c pthread_mutex_destroy
@c pthread_mutex_getprioceiling
@c pthread_mutex_init
@c pthread_mutex_lock
@c pthread_mutex_setprioceiling
@c pthread_mutex_timedlock
@c pthread_mutex_trylock
@c pthread_mutex_unlock
@c pthread_once
@c pthread_rwlockattr_destroy
@c pthread_rwlockattr_getkind_np
@c pthread_rwlockattr_getpshared
@c pthread_rwlockattr_init
@c pthread_rwlockattr_setkind_np
@c pthread_rwlockattr_setpshared
@c pthread_rwlock_destroy
@c pthread_rwlock_init
@c pthread_rwlock_rdlock
@c pthread_rwlock_timedrdlock
@c pthread_rwlock_timedwrlock
@c pthread_rwlock_tryrdlock
@c pthread_rwlock_trywrlock
@c pthread_rwlock_unlock
@c pthread_rwlock_wrlock
@c pthread_self
@c pthread_setaffinity_np
@c pthread_setcancelstate
@c pthread_setcanceltype
@c pthread_setconcurrency
@c pthread_setname_np
@c pthread_setschedparam
@c pthread_setschedprio
@c pthread_sigmask
@c pthread_sigqueue
@c pthread_spin_destroy
@c pthread_spin_init
@c pthread_spin_lock
@c pthread_spin_trylock
@c pthread_spin_unlock
@c pthread_testcancel
@c pthread_timedjoin_np
@c pthread_tryjoin_np
@c pthread_yield