threads(5)						Standards, Environments, and Macros						threads(5)

NAME

       threads, pthreads - POSIX pthreads and Solaris threads concepts

SYNOPSIS

   POSIX
       cc -mt [ flag... ] file... -lpthread [ -lrt library... ]

       #include <pthread.h>

   Solaris
       cc -mt [ flag... ] file... [ library... ]

       #include <sched.h>

       #include <thread.h>

DESCRIPTION

       POSIX  and Solaris threads each have their own implementation of the threads library. The  libpthread library is associated with POSIX; the
       libthread library is associated with Solaris. Both implementations are interoperable, their functionality similar, and can be  used  within
       the  same  application.	Only  POSIX  threads  are guaranteed to be fully portable to other POSIX-compliant environments. POSIX and Solaris
       threads require different source, include files and linking libraries. See SYNOPSIS.

   Similarities
       Most of the functions in the libpthread and libthread, libraries have a counterpart in the  other  corresponding  library.  POSIX  function
       names,  with  the exception of the semaphore names, have a "pthread" prefix. Function names for similar POSIX and Solaris have similar end-
       ings. Typically, similar POSIX and Solaris functions have the same number and use of arguments.

   Differences
       POSIX pthreads and Solaris threads differ in the following ways:

	 o  POSIX threads are more portable.

	 o  POSIX threads establish characteristics  for each thread according to configurable attribute objects.

	 o  POSIX pthreads implement thread cancellation.

	 o  POSIX pthreads enforce scheduling algorithms.

	 o  POSIX pthreads allow for clean-up handlers for fork(2) calls.

	 o  Solaris threads can be suspended and continued.

	 o  Solaris threads implement interprocess robust mutex locks.

	 o  Solaris threads implement daemon threads, for whose demise the process does not wait.

Function Comparison
       The following table compares the POSIX pthreads and Solaris threads functions. When a comparable interface is not available either in POSIX
       pthreads  or Solaris threads, a hyphen (-) appears in the column.

   Functions Related to Creation
	     POSIX (libpthread) 	    Solaris (libthread)
       pthread_create() 		thr_create()
       pthread_attr_init()		-
       pthread_attr_setdetachstate()	-
       pthread_attr_getdetachstate()	-
       pthread_attr_setinheritsched()	-
       pthread_attr_getinheritsched()	-
       pthread_attr_setschedparam()	-
       pthread_attr_getschedparam()	-

       pthread_attr_setschedpolicy()	-
       pthread_attr_getschedpolicy()	-
       pthread_attr_setscope()		-
       pthread_attr_getscope()		-
       pthread_attr_setstackaddr()	-
       pthread_attr_getstackaddr()	-
       pthread_attr_setstacksize()	-
       pthread_attr_getstacksize()	-
       pthread_attr_getguardsize()	-
       pthread_attr_setguardsize()	-
       pthread_attr_destroy()		-
       -				thr_min_stack()

   Functions Related to Exit
	   POSIX (libpthread)		 Solaris (libthread)
       pthread_exit()		     thr_exit()
       pthread_join()		     thr_join()
       pthread_detach() 	     -

   Functions Related to Thread Specific Data
	   POSIX (libpthread)		 Solaris (libthread)
       pthread_key_create()	     thr_keycreate()
       pthread_setspecific()	     thr_setspecific()
       pthread_getspecific()	     thr_getspecific()
       pthread_key_delete()	     -

   Functions Related to Signals
	   POSIX (libpthread)		 Solaris (libthread)
       pthread_sigmask()	     thr_sigsetmask()
       pthread_kill()		     thr_kill()

   Functions Related to IDs
	   POSIX (libpthread)		 Solaris (libthread)
       pthread_self()		     thr_self()
       pthread_equal()		     -
       -			     thr_main()

   Functions Related to Scheduling
	   POSIX (libpthread)		 Solaris (libthread)
       -			     thr_yield()
       -			     thr_suspend()
       -			     thr_continue()
       pthread_setconcurrency()      thr_setconcurrency()
       pthread_getconcurrency()      thr_getconcurrency()
       pthread_setschedparam()	     thr_setprio()
       pthread_getschedparam()	     thr_getprio()

   Functions Related to Cancellation
	   POSIX (libpthread)		 Solaris (libthread)
       pthread_cancel() 	     -
       pthread_setcancelstate()      -
       pthread_setcanceltype()	     -
       pthread_testcancel()	     -
       pthread_cleanup_pop()	     -
       pthread_cleanup_push()	     -

   Functions Related to Mutexes
		 POSIX (libpthread)		Solaris (libthread)

       pthread_mutex_init()			mutex_init()
       pthread_mutexattr_init() 		-
       pthread_mutexattr_setpshared()		-
       pthread_mutexattr_getpshared()		-
       pthread_mutexattr_setprotocol()		-
       pthread_mutexattr_getprotocol()		-
       pthread_mutexattr_setprioceiling()	-
       pthread_mutexattr_getprioceiling()	-
       pthread_mutexattr_settype()		-
       pthread_mutexattr_gettype()		-
       pthread_mutexattr_destroy()		-
       pthread_mutex_setprioceiling()		-
       pthread_mutex_getprioceiling()		-
       pthread_mutex_lock()			mutex_lock()
       pthread_mutex_trylock()			mutex_trylock()
       pthread_mutex_unlock()			mutex_unlock()
       pthread_mutex_destroy()			mutex_destroy()

   Functions Related to Condition Variables
	    POSIX (libpthread)		   Solaris (libthread)
       pthread_cond_init()	       cond_init()
       pthread_condattr_init()	       -
       pthread_condattr_setpshared()   -
       pthread_condattr_getpshared()   -
       pthread_condattr_destroy()      -
       pthread_cond_wait()	       cond_wait()
       pthread_cond_timedwait()        cond_timedwait()
       pthread_cond_signal()	       cond_signal()
       pthread_cond_broadcast()        cond_broadcast()
       pthread_cond_destroy()	       cond_destroy()

   Functions Related to Reader/Writer Locking
	     POSIX (libpthread) 	     Solaris (libthread)
       pthread_rwlock_init()		 rwlock_init()
       pthread_rwlock_rdlock()		 rw_rdlock()
       pthread_rwlock_tryrdlock()	 rw_tryrdlock()
       pthread_rwlock_wrlock()		 rw_wrlock()
       pthread_rwlock_trywrlock()	 rw_trywrlock()
       pthread_rwlock_unlock()		 rw_unlock()
       pthread_rwlock_destroy() 	 rwlock_destroy()
       pthread_rwlockattr_init()	 -
       pthread_rwlockattr_destroy()	 -
       pthread_rwlockattr_getpshared()	 -
       pthread_rwlockattr_setpshared()	 -

   Functions Related to Semaphores
	   POSIX (libpthread)		 Solaris (libthread)
       sem_init()		     sema_init()
       sem_open()		     -
       sem_close()		     -
       sem_wait()		     sema_wait()
       sem_trywait()		     sema_trywait()
       sem_post()		     sema_post()
       sem_getvalue()		     -
       sem_unlink()		     -
       sem_destroy()		     sema_destroy()

   Functions Related to fork() Clean Up
	   POSIX (libpthread)		 Solaris (libthread)
       pthread_atfork() 	     -

   Functions Related to Limits
	   POSIX (libpthread)		 Solaris (libthread)
       pthread_once()		     -

   Functions Related to Debugging
	   POSIX (libpthread)		 Solaris (libthread)
       -			     thr_stksegment()

LOCKING

   Synchronization
       POSIX (libpthread)	  Solaris (libthread) Multi-threaded behavior is asynchronous, and therefore,  optimized for concurrent and paral-
       lel processing. As threads, always from within the same process and  sometimes from multiple processes, share global data with each  other,
       they  are  not  guaranteed  exclusive  access  to  the  shared data at any point in time. Securing mutually exclusive access to shared data
       requires  synchronization among the threads. Both POSIX and Solaris implement four synchronization  mechanisms:	mutexes,  condition  vari-
       ables, reader/writer locking  (optimized frequent-read occasional-write mutex), and semaphores.

       Synchronizing  multiple	threads  diminishes  their concurrency. The coarser the grain of synchronization, that is, the larger the block of
       code that is locked, the lesser the concurrency.

   MT fork()
       If a POSIX threads program calls fork(2), it implicitly calls fork1(2), which replicates only the calling thread. Should there be any  out-
       standing  mutexes  throughout  the  process,  the application should call pthread_atfork(3C) to wait for and acquire those mutexes prior to
       calling fork().

SCHEDULING

   POSIX
       Scheduling allocation size per thread is greater than one. POSIX supports the following three scheduling policies:

       SCHED_OTHER     Timesharing (TS) scheduling policy. It is based on the timesharing scheduling class.

       SCHED_FIFO      First-In-First-Out (FIFO) scheduling policy. Threads scheduled to this policy, if not pre-empted by a higher priority, will
		       proceed	until completion. Threads whose contention scope is system (PTHREAD_SCOPE_SYSTEM) are in real-time (RT) scheduling
		       class. The calling process must have a effective user ID of 0. SCHED_FIFO for  threads  whose  contention  scope's  process
		       (PTHREAD_SCOPE_PROCESS) is based on the TS scheduling class.

       SCHED_RR        Round-Robin scheduling policy. Threads scheduled to this policy, if not pre-empted by a higher priority, will execute for a
		       time period determined by the system. Threads whose contention scope is system (PTHREAD_SCOPE_SYSTEM) are in real-time (RT)
		       scheduling class and the calling process must have a effective user ID of 0. SCHED_RR for threads whose contention scope is
		       process (PTHREAD_SCOPE_PROCESS) is based on the TS scheduling class.

   Solaris
       Only scheduling policy supported is SCHED_OTHER, which is timesharing, based on the TS scheduling class.

ERRORS

       In a multi-threaded application, linked with libpthread or libthread, EINTR may be returned whenever another thread calls   fork(2),  which
       calls  fork1(2) instead. To ensure proper library linking order, use this option, rather than -lthread, to link with libthread.

USAGE

   -mt compiler option
       The  -mt compiler option compiles and links for multithreaded code. It compiles source files with -D_REENTRANT and augments the set of sup-
       port libraries to include -lthread in the required order.

       To ensure proper library linking order, use this option rather than -lthread to link with libthread.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe, Fork 1-Safe	   |
       +-----------------------------+-----------------------------+

SEE ALSO

       crle(1), fork(2), libpthread(3LIB), librt(3LIB), libthread(3LIB), pthread_atfork(3C), pthread_create(3C), attributes(5), standards(5)

       Linker and Libraries Guide

SunOS 5.10							    20 Aug 2003 							threads(5)