libthread(3THR)
NAME | SYNOPSIS | DESCRIPTION | Function Comparison | LOCKING | SCHEDULING | ALTERNATE IMPLEMENTATION | ERRORS | ATTRIBUTES | FILES | SEE ALSO
NAME
- threads, pthreads, libpthread, libthread- concepts related
to POSIX pthreads and Solaris threads and the libpthread and libthread libraries
SYNOPSIS
cc -mt [ flag... ] file...- lpthread [ -lposix4 library... ]
#include <pthread.h>
Solaris
cc - mt [ flag... ] file...[ library... ]
#include <sched.h>
#include <thread.h>
DESCRIPTION
-
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.
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:
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
Functions Related to IDs
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
Functions Related to Limits
Functions Related to Debugging
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
- 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.
POSIX
Scheduling allocation size per thread is greater than one. POSIX supports the following three scheduling policies:
Solaris
Only scheduling policy supported is SCHED_OTHER, which is timesharing, based on the TS scheduling class.
ALTERNATE IMPLEMENTATION
The standard threads implementation is a two-level model in which user-level threads are multiplexed over possibly fewer lightweight processes, or LWP s. An LWP is the fundamental unit of execution that is dispatched to a processor by the operating system.
The system provides an alternate threads implementation, a one-level model, in which user-level threads are associated one-to-one with LWP s. This implementation is simpler than the standard implementation and may be beneficial to some multithreaded applications. It provides exactly the same interfaces, both for POSIX threads and Solaris threads, as the standard implementation.
To link with the alternate implementation, use the following runpath (-R ) options when linking the program:
POSIX
cc -mt ... -lpthread ... -R /usr/lib/lwp (32-bit) cc -mt ... -lpthread ... -R /usr/lib/lwp/64 (64-bit) |
Solaris
cc -mt ... -R /usr/lib/lwp (32-bit) cc -mt ... -R /usr/lib/lwp/64 (64-bit) |
For multithreaded programs that have been previously linked with the standard threads library, the environment variables LD_LIBRARY_PATH and LD_LIBRARY_PATH_64 can be set as follows to bind the program at runtime to the alternate threads library:
LD_LIBRARY_PATH=/usr/lib/lwp LD_LIBRARY_PATH_64=/usr/lib/lwp/64 |
Note that if an LD_LIBRARY_PATH environment variable is in effect for a secure process, then only the trusted directories specified by this variable will be used to augment the runtime linker's search rules.
The runtime linker may also be instructed to use this libthread by establishing an alternative object cache; see crle(1) with the -a option.
When using the alternate one-level threads implementation, be aware that it may create more LWP s than the standard implementation using unbound threads. LWP s consume operating system memory in contrast to threads, which consume only user-level memory. Thus a multithreaded application linked against this library that creates thousands of threads would create an equal number of LWP s and might run the system out of resources required to support the application.
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.
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/libposix4.*
Solaris
/usr/include/thread.h /usr/include/sched.h /lib/libthread.*
SEE ALSO
crle(1) , fork(2) , pthread_atfork(3THR) , pthread_create(3THR) , attributes(5) , standards(5)
Linker and Libraries Guide
NAME | SYNOPSIS | DESCRIPTION | Function Comparison | LOCKING | SCHEDULING | ALTERNATE IMPLEMENTATION | ERRORS | ATTRIBUTES | FILES | SEE ALSO
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