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)