threads
, pthreads
- POSIX pthreads and Solaris threads concepts
Synopsis
POSIX
cc –mt [flag... ]file... [ -lrtlibrary... ]
#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 withinlibc(3LIB). Bothimplementations are interoperable, their functionality similar, and can be used within the sameapplication. Only POSIX threads are guaranteed to be fully portable to otherPOSIX-compliant environments. POSIX and Solaris threads require different source, include files andlinking libraries. SeeSYNOPSIS.
Similarities
Most of the POSIX and Solaris threading functions have counterparts with eachother. POSIX function names, with the exception of the semaphore names, havea “pthread” prefix. Function names for similar POSIX and Solaris functions havesimilar endings. Typically, similar POSIX and Solaris functions have the same number anduse 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 forfork(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. Whena comparable interface is not available either in POSIX pthreads orSolaris 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() |
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Functions Related to Exit
POSIX | Solaris | pthread_exit() | thr_exit() | pthread_join() | thr_join() | pthread_detach() | – |
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Functions Related to Thread Specific Data
POSIX | Solaris | pthread_key_create() | thr_keycreate() | pthread_setspecific() | thr_setspecific() | pthread_getspecific() | thr_getspecific() | pthread_key_delete() | – |
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Functions Related to Signals
POSIX | Solaris | pthread_sigmask() | thr_sigsetmask() | pthread_kill() | thr_kill() |
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Functions Related to IDs
POSIX | Solaris | pthread_self() | thr_self() | pthread_equal() | – | – | thr_main() |
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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() |
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Functions Related to Cancellation
POSIX | Solaris | pthread_cancel() | – | pthread_setcancelstate() | – | pthread_setcanceltype() | – | pthread_testcancel() | – | pthread_cleanup_pop() | – | pthread_cleanup_push() | – |
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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() |
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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() |
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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() | – |
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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() |
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Functions Related to fork( ) Clean Up
POSIX | Solaris | pthread_atfork() | – |
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Functions Related to Limits
POSIX | Solaris | pthread_once() | – |
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Functions Related to Debugging
POSIX | Solaris | – | thr_stksegment() |
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Locking
Synchronization
Multithreaded behavior is asynchronous, and therefore, optimized for concurrent and parallelprocessing. As threads, always from within the same process and sometimesfrom multiple processes, share global data with each other, they are notguaranteed exclusive access to the shared data at any point in time. Securingmutually exclusive access to shared data requires synchronization among the threads.Both POSIX and Solaris implement four synchronization mechanisms: mutexes, condition variables, reader/writerlocking (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, thelesser the concurrency.
MTfork()
If a threads program callsfork(2), it implicitly callsfork1(2), which replicatesonly the calling thread. Should there be any outstanding mutexes throughout theprocess, the application should callpthread_atfork(3C) to wait for and acquire thosemutexes prior to callingfork().
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 the {PRIV_PROC_PRIOCNTL} privilege asserted in its effective set.
- 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 the {PRIV_PROC_PRIOCNTL} privilege asserted in its effective set.
In addition to the POSIX-specified scheduling policies above, Solaris also supports thesescheduling policies:
- SCHED_IA
Threads are scheduled according to the Inter-Active Class (IA) policy as described inpriocntl(2).
- SCHED_FSS
Threads are scheduled according to the Fair-Share Class (FSS) policy as described inpriocntl(2).
- SCHED_FX
Threads are scheduled according to the Fixed-Priority Class (FX) policy as described inpriocntl(2).
Solaris Threads
Only scheduling policy supported isSCHED_OTHER, which is timesharing, based on theTS scheduling class.
Errors
In a multithreaded application,EINTR can be returned from blocking system callswhen another thread callsforkall(2).
Usage
-mt compiler option
The-mt compiler option compiles and links for multithreaded code. It compilessource files with -D_REENTRANT and augments the set of support libraries properly.
Attributes
Seeattributes(5) for descriptions of the following attributes:
ATTRIBUTE TYPE | ATTRIBUTE VALUE |
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MT-Level | MT-Safe, Fork 1-Safe |
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See Also
crle(1),fork(2),priocntl(2),libpthread(3LIB),librt(3LIB),libthread(3LIB),pthread_atfork(3C),pthread_create(3C),attributes(5),privileges(5),standards(5)
Linker and Libraries Guide
