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Full Discussion: Threading...
Top Forums UNIX for Dummies Questions & Answers Threading... Post 302088576 by jim mcnamara on Wednesday 13th of September 2006 09:55:42 AM
Old 09-13-2006
In UNIX, you can generally think of a thread as a process that has its own stack for registers but shares code and data with the parent process - and the other threads.

For that reason, thread scheduling can be implemented a lot like process scheduling - ie, there is usually a quantum (time slice) allocated to a process/thread that has the cpu -- threading works much more efficiently in a multi-cpu environment. When the quantum is up and somebody else wants the cpu and is of equal priority, the other guy gets the cpu. Any thread or process with higher priority will pre-empt the cpu from the running process.

So, the answer to your question is: assuming all threads have equal priority - no the other guys will not have to wait. Unless the calculating thread has a mutex the other guys are waiting on. You can implement single-thread priority by using a mutex in other words.

Try man pthread to see what thread scheduling options (if more than one) your implementation of UNIX supports.
 

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LEARN ABOUT CENTOS

pthread_setschedprio

PTHREAD_SETSCHEDPRIO(3) 				     Linux Programmer's Manual					   PTHREAD_SETSCHEDPRIO(3)

NAME

       pthread_setschedprio - set scheduling priority of a thread

SYNOPSIS

       #include <pthread.h>

       pthread_setschedprio(pthread_t thread, int prio);

       Compile and link with -pthread.

DESCRIPTION

       The  pthread_setschedprio()  function  sets  the  scheduling  priority  of  the thread thread to the value specified in prio.  (By contrast
       pthread_setschedparam(3) changes both the scheduling policy and priority of a thread.)

RETURN VALUE

       On success, this function returns 0; on error, it returns a nonzero error number.  If pthread_setschedprio() fails, the scheduling priority
       of thread is not changed.

ERRORS

       EINVAL prio is not valid for the scheduling policy of the specified thread.

       EPERM  The caller does not have appropriate privileges to set the specified priority.

       ESRCH  No thread with the ID thread could be found.

       POSIX.1-2001 also documents an ENOTSUP ("attempt was made to set the priority to an unsupported value") error for pthread_setschedparam(3).

VERSIONS

       This function is available in glibc since version 2.3.4.

CONFORMING TO

       POSIX.1-2001.

NOTES

       For  a description of the permissions required to, and the effect of, changing a thread's scheduling priority, and details of the permitted
       ranges for priorities in each scheduling policy, see sched_setscheduler(2).

SEE ALSO

       getrlimit(2), sched_get_priority_min(2), sched_setscheduler(2), pthread_attr_init(3), pthread_attr_setinheritsched(3),
       pthread_attr_setschedparam(3), pthread_attr_setschedpolicy(3), pthread_create(3), pthread_self(3), pthread_setschedparam(3), pthreads(7)

COLOPHON

       This page is part of release 3.53 of the Linux man-pages project.  A description of the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    2008-11-06						   PTHREAD_SETSCHEDPRIO(3)
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