threads(3THR) (man pages section 3: Threads and Realtime Library Functions)

man pages section 3: Threads and Realtime Library Functions

threads(3THR)

NAME

threads, pthreads- concepts related to POSIX pthreads and Solaris threads and the libpthread and libthread libraries

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 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 an optimized mutex and interprocess robust mutex locks.
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 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 POSIX 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(3THR), 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 support 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

FILES

POSIX

/usr/include/pthread.h /lib/libpthread.* /lib/librt.*

Solaris

/usr/include/thread.h /usr/include/sched.h /lib/libthread.*

threads(3THR)

NAME

SYNOPSIS

POSIX

Solaris

DESCRIPTION

Similarities

Differences

Function Comparison

Functions Related to Creation

Functions Related to Exit

Functions Related to Thread Specific Data

Functions Related to Signals

Functions Related to IDs

Functions Related to Scheduling

Functions Related to Cancellation

Functions Related to Mutexes

Functions Related to Condition Variables

Functions Related to Reader/Writer Locking

Functions Related to Semaphores

Functions Related to fork() Clean Up

Functions Related to Limits

Functions Related to Debugging

LOCKING

Synchronization

MT fork()

SCHEDULING

POSIX

Solaris

ERRORS

USAGE

-mt compiler option

ATTRIBUTES

FILES

POSIX

Solaris

SEE ALSO

`-mt` compiler option