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

NAME

       threads, pthreads - POSIX pthreads and Solaris threads concepts

SYNOPSIS

   POSIX
       cc -mt [ flag... ] file... [ -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 within libc(3LIB). 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 envi-
       ronments. POSIX and Solaris threads require different source, include files and linking libraries. See SYNOPSIS.

   Similarities
       Most  of the POSIX and Solaris threading functions have counterparts with each other. POSIX function names, with the exception of the sema-
       phore names, have a "pthread" prefix. Function names for similar POSIX and Solaris functions have similar endings. 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 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				Solaris
       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			     Solaris
       pthread_exit()		     thr_exit()
       pthread_join()		     thr_join()
       pthread_detach() 	     -

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

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

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

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

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

   Functions Related to Mutexes
       POSIX					Solaris

       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_setrobust()		-
       pthread_mutexattr_getrobust()		-
       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			       Solaris
       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				 Solaris
       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			     Solaris
       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			     Solaris
       pthread_atfork() 	     -

   Functions Related to Limits
       POSIX			     Solaris
       pthread_once()		     -

   Functions Related to Debugging
       POSIX			     Solaris
       -			     thr_stksegment()

LOCKING

   Synchronization
       Multithreaded behavior is asynchronous, and therefore,  optimized for concurrent and parallel 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 variables, reader/writer locking  (optimized frequent-read occa-
       sional-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 threads program calls fork(2), it implicitly calls fork1(2), which replicates only the calling thread. Should there be any outstanding
       mutexes throughout the process, the application should call pthread_atfork(3C) to wait for and  acquire	those  mutexes	prior  to  calling
       fork().

SCHEDULING

   POSIX Threads
       Solaris supports the following three POSIX scheduling policies:

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

       SCHED_FIFO     First-In-First-Out  scheduling policy. Threads scheduled to this policy, if not preempted by a higher priority, will proceed
		      until completion. Such threads are in real-time (RT) scheduling class. The calling process must have a effective user ID	of
		      0.

       SCHED_RR       Round-Robin  scheduling  policy. Threads scheduled to this policy, if not preempted by a higher priority, will execute for a
		      time period determined by the system. Such threads are in real-time (RT) scheduling class and the calling process must  have
		      a effective user ID of 0.

       In addition to the POSIX-specified scheduling policies above, Solaris also supports these scheduling policies:

       SCHED_IA     Threads are scheduled according to the Inter-Active Class (IA) policy as described in priocntl(2).

       SCHED_FSS    Threads are scheduled according to the Fair-Share Class (FSS) policy as described in priocntl(2).

       SCHED_FX     Threads are scheduled according to the Fixed-Priority Class (FX) policy as described in priocntl(2).

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

ERRORS

       In a multithreaded application, EINTR can be returned from blocking system calls when another thread calls  forkall(2).

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 properly.

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), priocntl(2), libpthread(3LIB), librt(3LIB), libthread(3LIB), pthread_atfork(3C), pthread_create(3C), attributes(5), stan-
       dards(5)

       Linker and Libraries Guide

SunOS 5.11							    11 Nov 2008 							threads(5)