path: root/usr/src/man/man5/threads.5

'\" te
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.TH THREADS 5 "Nov 11, 2008"
.SH NAME
threads, pthreads \- POSIX pthreads and Solaris threads concepts
.SH SYNOPSIS
.SS "POSIX"
.LP
.nf
cc -mt [ \fIflag\fR... ] \fIfile\fR... [ -lrt \fIlibrary\fR... ]
.fi

.LP
.nf
#include <pthread.h>
.fi

.SS "Solaris"
.LP
.nf
cc -mt [ \fIflag\fR... ] \fIfile\fR... [ \fIlibrary\fR... ]
.fi

.LP
.nf
#include <sched.h>
.fi

.LP
.nf
#include <thread.h>
.fi

.SH DESCRIPTION
.sp
.LP
POSIX and Solaris threads each have their own implementation within
\fBlibc\fR(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 \fBSYNOPSIS\fR.
.SS "Similarities"
.sp
.LP
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
"\fBpthread\fR" 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.
.SS "Differences"
.sp
.LP
POSIX pthreads and Solaris threads differ in the following ways:
.RS +4
.TP
.ie t \(bu
.el o
POSIX threads are more portable.
.RE
.RS +4
.TP
.ie t \(bu
.el o
POSIX threads establish characteristics  for each thread according to
configurable attribute objects.
.RE
.RS +4
.TP
.ie t \(bu
.el o
POSIX pthreads implement thread cancellation.
.RE
.RS +4
.TP
.ie t \(bu
.el o
POSIX pthreads enforce scheduling algorithms.
.RE
.RS +4
.TP
.ie t \(bu
.el o
POSIX pthreads allow for clean-up handlers for \fBfork\fR(2) calls.
.RE
.RS +4
.TP
.ie t \(bu
.el o
Solaris threads can be suspended and continued.
.RE
.RS +4
.TP
.ie t \(bu
.el o
Solaris threads implement daemon threads, for whose demise the process does not
wait.
.RE
.SH FUNCTION COMPARISON
.sp
.LP
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 (\fB-\fR) appears in the column.
.SS "Functions Related to Creation"
.sp

.sp
.TS
l l
l l .
\fBPOSIX\fR	\fBSolaris\fR
\fBpthread_create()\fR	\fBthr_create()\fR
\fBpthread_attr_init()\fR	\fB-\fR
\fBpthread_attr_setdetachstate()\fR	\fB-\fR
\fBpthread_attr_getdetachstate()\fR	\fB-\fR
\fBpthread_attr_setinheritsched()\fR	\fB-\fR
\fBpthread_attr_getinheritsched()\fR	\fB-\fR
\fBpthread_attr_setschedparam()\fR	\fB-\fR
\fBpthread_attr_getschedparam()\fR	\fB-\fR
\fBpthread_attr_setschedpolicy()\fR	\fB-\fR
\fBpthread_attr_getschedpolicy()\fR	\fB-\fR
\fBpthread_attr_setscope()\fR	\fB-\fR
\fBpthread_attr_getscope()\fR	\fB-\fR
\fBpthread_attr_setstackaddr()\fR	\fB-\fR
\fBpthread_attr_getstackaddr()\fR	\fB-\fR
\fBpthread_attr_setstacksize()\fR	\fB-\fR
\fBpthread_attr_getstacksize()\fR	\fB-\fR
\fBpthread_attr_getguardsize()\fR	\fB-\fR
\fBpthread_attr_setguardsize()\fR	\fB-\fR
\fBpthread_attr_destroy()\fR	\fB-\fR
\fB-\fR	\fBthr_min_stack()\fR
.TE

.SS "Functions Related to Exit"
.sp

.sp
.TS
l l
l l .
\fBPOSIX\fR	\fBSolaris\fR
\fBpthread_exit()\fR	\fBthr_exit()\fR
\fBpthread_join()\fR	\fBthr_join()\fR
\fBpthread_detach()\fR	\fB-\fR
.TE

.SS "Functions Related to Thread Specific Data"
.sp

.sp
.TS
l l
l l .
\fBPOSIX\fR	\fBSolaris\fR
\fBpthread_key_create()\fR	\fBthr_keycreate()\fR
\fBpthread_setspecific()\fR	\fBthr_setspecific()\fR
\fBpthread_getspecific()\fR	\fBthr_getspecific()\fR
\fBpthread_key_delete()\fR	\fB-\fR
.TE

.SS "Functions Related to Signals"
.sp

.sp
.TS
l l
l l .
\fBPOSIX\fR	\fBSolaris\fR
\fBpthread_sigmask()\fR	\fBthr_sigsetmask()\fR
\fBpthread_kill()\fR	\fBthr_kill()\fR
.TE

.SS "Functions Related to IDs"
.sp

.sp
.TS
l l
l l .
\fBPOSIX\fR	\fBSolaris\fR
\fBpthread_self()\fR	\fBthr_self()\fR
\fBpthread_equal()\fR	\fB-\fR
\fB-\fR	\fBthr_main()\fR
.TE

.SS "Functions Related to Scheduling"
.sp

.sp
.TS
l l
l l .
\fBPOSIX\fR	\fBSolaris\fR
\fB-\fR	\fBthr_yield()\fR
\fB-\fR	\fBthr_suspend()\fR
\fB-\fR	\fBthr_continue()\fR
\fBpthread_setconcurrency()\fR	\fBthr_setconcurrency()\fR
\fBpthread_getconcurrency()\fR	\fBthr_getconcurrency()\fR
\fBpthread_setschedparam()\fR	\fBthr_setprio()\fR
\fBpthread_setschedprio()\fR	\fBthr_setprio()\fR
\fBpthread_getschedparam()\fR	\fBthr_getprio()\fR
.TE

.SS "Functions Related to Cancellation"
.sp

.sp
.TS
l l
l l .
\fBPOSIX\fR	\fBSolaris\fR
\fBpthread_cancel()\fR	\fB-\fR
\fBpthread_setcancelstate()\fR	\fB-\fR
\fBpthread_setcanceltype()\fR	\fB-\fR
\fBpthread_testcancel()\fR	\fB-\fR
\fBpthread_cleanup_pop()\fR	\fB-\fR
\fBpthread_cleanup_push()\fR	\fB-\fR
.TE

.SS "Functions Related to Mutexes"
.sp

.sp
.TS
l l
l l .
\fBPOSIX\fR	\fBSolaris\fR
\fBpthread_mutex_init()\fR	\fBmutex_init()\fR
\fBpthread_mutexattr_init()\fR	\fB-\fR
\fBpthread_mutexattr_setpshared()\fR	\fB-\fR
\fBpthread_mutexattr_getpshared()\fR	\fB-\fR
\fBpthread_mutexattr_setprotocol()\fR	\fB-\fR
\fBpthread_mutexattr_getprotocol()\fR	\fB-\fR
\fBpthread_mutexattr_setprioceiling()\fR	\fB-\fR
\fBpthread_mutexattr_getprioceiling()\fR	\fB-\fR
\fBpthread_mutexattr_settype()\fR	\fB-\fR
\fBpthread_mutexattr_gettype()\fR	\fB-\fR
\fBpthread_mutexattr_setrobust()\fR	\fB-\fR
\fBpthread_mutexattr_getrobust()\fR	\fB-\fR
\fBpthread_mutexattr_destroy()\fR	\fB-\fR
\fBpthread_mutex_setprioceiling()\fR	\fB-\fR
\fBpthread_mutex_getprioceiling()\fR	\fB-\fR
\fBpthread_mutex_lock()\fR	\fBmutex_lock()\fR
\fBpthread_mutex_trylock()\fR	\fBmutex_trylock()\fR
\fBpthread_mutex_unlock()\fR	\fBmutex_unlock()\fR
\fBpthread_mutex_destroy()\fR	\fBmutex_destroy()\fR
.TE

.SS "Functions Related to Condition Variables"
.sp

.sp
.TS
l l
l l .
\fBPOSIX\fR	\fBSolaris\fR
\fBpthread_cond_init()\fR	\fBcond_init()\fR
\fBpthread_condattr_init()\fR	\fB-\fR
\fBpthread_condattr_setpshared()\fR	\fB-\fR
\fBpthread_condattr_getpshared()\fR	\fB-\fR
\fBpthread_condattr_destroy()\fR	\fB-\fR
\fBpthread_cond_wait()\fR	\fBcond_wait()\fR
\fBpthread_cond_timedwait()\fR	\fBcond_timedwait()\fR
\fBpthread_cond_signal()\fR	\fBcond_signal()\fR
\fBpthread_cond_broadcast()\fR	\fBcond_broadcast()\fR
\fBpthread_cond_destroy()\fR	\fBcond_destroy()\fR
.TE

.SS "Functions Related to Reader/Writer Locking"
.sp

.sp
.TS
l l
l l .
\fBPOSIX\fR	\fBSolaris\fR
\fBpthread_rwlock_init()\fR	\fBrwlock_init()\fR
\fBpthread_rwlock_rdlock()\fR	\fBrw_rdlock()\fR
\fBpthread_rwlock_tryrdlock()\fR	\fBrw_tryrdlock()\fR
\fBpthread_rwlock_wrlock()\fR	\fBrw_wrlock()\fR
\fBpthread_rwlock_trywrlock()\fR	\fBrw_trywrlock()\fR
\fBpthread_rwlock_unlock()\fR	\fBrw_unlock()\fR
\fBpthread_rwlock_destroy()\fR	\fBrwlock_destroy()\fR
\fBpthread_rwlockattr_init()\fR	\fB-\fR
\fBpthread_rwlockattr_destroy()\fR	\fB-\fR
\fBpthread_rwlockattr_getpshared()\fR	\fB-\fR
\fBpthread_rwlockattr_setpshared()\fR	\fB-\fR
.TE

.SS "Functions Related to Semaphores"
.sp

.sp
.TS
l l
l l .
\fBPOSIX\fR	\fBSolaris\fR
\fBsem_init()\fR	\fBsema_init()\fR
\fBsem_open()\fR	\fB-\fR
\fBsem_close()\fR	\fB-\fR
\fBsem_wait()\fR	\fBsema_wait()\fR
\fBsem_trywait()\fR	\fBsema_trywait()\fR
\fBsem_post()\fR	\fBsema_post()\fR
\fBsem_getvalue()\fR	\fB-\fR
\fBsem_unlink()\fR	\fB-\fR
\fBsem_destroy()\fR	\fBsema_destroy()\fR
.TE

.SS "Functions Related to fork(\|) Clean Up"
.sp

.sp
.TS
l l
l l .
\fBPOSIX\fR	\fBSolaris\fR
\fBpthread_atfork()\fR	\fB-\fR
.TE

.SS "Functions Related to Limits"
.sp

.sp
.TS
l l
l l .
\fBPOSIX\fR	\fBSolaris\fR
\fBpthread_once()\fR	\fB-\fR
.TE

.SS "Functions Related to Debugging"
.sp

.sp
.TS
l l
l l .
\fBPOSIX\fR	\fBSolaris\fR
\fB-\fR	\fBthr_stksegment()\fR
.TE

.SH LOCKING
.SS "Synchronization"
.sp
.LP
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
(\fIoptimized frequent-read occasional-write mutex\fR), and semaphores.
.sp
.LP
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.
.SS "MT \fBfork()\fR"
.sp
.LP
If a threads program calls \fBfork\fR(2), it implicitly calls \fBfork1\fR(2),
which replicates only the calling thread. Should there be any outstanding
mutexes throughout the process, the application should call
\fBpthread_atfork\fR(3C) to wait for and acquire those mutexes prior to calling
\fBfork()\fR.
.SH SCHEDULING
.SS "POSIX Threads"
.sp
.LP
Solaris supports the following three POSIX scheduling policies:
.sp
.ne 2
.na
\fB\fBSCHED_OTHER\fR\fR
.ad
.RS 15n
Traditional Timesharing scheduling policy. It is based on the timesharing (TS)
scheduling class.
.RE

.sp
.ne 2
.na
\fB\fBSCHED_FIFO\fR\fR
.ad
.RS 15n
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 a effective
user \fBID\fR of \fB0\fR.
.RE

.sp
.ne 2
.na
\fB\fBSCHED_RR\fR\fR
.ad
.RS 15n
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 a effective user \fBID\fR of \fB0\fR.
.RE

.sp
.LP
In addition to the POSIX-specified scheduling policies above, Solaris also
supports these scheduling policies:
.sp
.ne 2
.na
\fB\fBSCHED_IA\fR\fR
.ad
.RS 13n
Threads are scheduled according to the Inter-Active Class (IA) policy as
described in \fBpriocntl\fR(2).
.RE

.sp
.ne 2
.na
\fB\fBSCHED_FSS\fR\fR
.ad
.RS 13n
Threads are scheduled according to the Fair-Share Class (FSS) policy as
described in \fBpriocntl\fR(2).
.RE

.sp
.ne 2
.na
\fB\fBSCHED_FX\fR\fR
.ad
.RS 13n
Threads are scheduled according to the Fixed-Priority Class (FX) policy as
described in \fBpriocntl\fR(2).
.RE

.SS "Solaris Threads"
.sp
.LP
Only scheduling policy supported is \fBSCHED_OTHER\fR, which is timesharing,
based on the \fBTS\fR scheduling class.
.SH ERRORS
.sp
.LP
In a multithreaded application, \fBEINTR\fR can be returned from blocking
system calls when another thread calls  \fBforkall\fR(2).
.SH USAGE
.SS "\fB-mt\fR compiler option"
.sp
.LP
The \fB-mt\fR compiler option compiles and links for multithreaded code. It
compiles source files with \(mi\fBD_REENTRANT\fR and augments the set of
support libraries properly.
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
MT-Level	MT-Safe, Fork 1-Safe
.TE

.SH SEE ALSO
.sp
.LP
\fBcrle\fR(1), \fBfork\fR(2), \fBpriocntl\fR(2), \fBlibpthread\fR(3LIB),
\fBlibrt\fR(3LIB), \fBlibthread\fR(3LIB), \fBpthread_atfork\fR(3C),
\fBpthread_create\fR(3C), \fBattributes\fR(5), \fBstandards\fR(5)
.sp
.LP
\fILinker and Libraries Guide\fR