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pthreads(5)

Name | Synopsis | Description | Function Comparison | Locking | SCHEDULING | Errors | Usage | Attributes | See Also

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 environments. 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 semaphore 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:

      • POSIX threads are more portable.

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

      • POSIX pthreads implement thread cancellation.

      • POSIX pthreads enforce scheduling algorithms.

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

      • Solaris threads can be suspended and continued.

      • 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_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_np()

      –

      pthread_mutexattr_getrobust_np()

      –

      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 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 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

      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. 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 pre-empted 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.

    Solaris

      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 support 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

SunOS 5.10  Last Revised 11 Aug 2006

Name | Synopsis | Description | Function Comparison | Locking | SCHEDULING | Errors | Usage | Attributes | See Also