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Man Pages


Manual Reference Pages  -  RTPRIO_THREAD (2)

NAME

rtprio, rtprio_thread - examine or modify realtime or idle priority

CONTENTS

Library
Synopsis
Description
Return Values
Errors
See Also
Authors

LIBRARY


.Lb libc

SYNOPSIS


.In sys/types.h
.In sys/rtprio.h int rtprio int function pid_t pid struct rtprio *rtp int rtprio_thread int function lwpid_t lwpid struct rtprio *rtp

DESCRIPTION

The rtprio system call is used to lookup or change the realtime or idle priority of a process, or the calling thread. The rtprio_thread system call is used to lookup or change the realtime or idle priority of a thread.

The function argument specifies the operation to be performed. RTP_LOOKUP to lookup the current priority, and RTP_SET to set the priority.

For the rtprio system call, the pid argument specifies the process to operate on, 0 for the calling thread. When pid is non-zero, the system call reports the highest priority in the process, or sets all threads’ priority in the process, depending on value of the function argument.

For the rtprio_thread system call, the lwpid specifies the thread to operate on, 0 for the calling thread.

The *rtp argument is a pointer to a struct rtprio which is used to specify the priority and priority type. This structure has the following form:

struct rtprio {
        u_short type;
        u_short prio;
};

The value of the type field may be RTP_PRIO_REALTIME for realtime priorities, RTP_PRIO_NORMAL for normal priorities, and RTP_PRIO_IDLE for idle priorities. The priority specified by the prio field ranges between 0 and RTP_PRIO_MAX (usually 31). 0 is the highest possible priority.

Realtime and idle priority is inherited through fork() and exec().

A realtime thread can only be preempted by a thread of equal or higher priority, or by an interrupt; idle priority threads will run only when no other real/normal priority thread is runnable. Higher real/idle priority threads preempt lower real/idle priority threads. Threads of equal real/idle priority are run round-robin.

RETURN VALUES


.Rv -std rtprio rtprio_thread

ERRORS

The rtprio and rtprio_thread system calls will fail if:
[EFAULT]
  The rtp pointer passed to rtprio or rtprio_thread was invalid.
[EINVAL]
  The specified prio was out of range.
[EPERM]
  The calling thread is not allowed to set the realtime priority. Only root is allowed to change the realtime priority of any thread, and non-root may only change the idle priority of threads the user owns, when the sysctl(8) variable security.bsd.unprivileged_idprio is set to non-zero.
[ESRCH]
  The specified process or thread was not found or visible.

SEE ALSO

nice(1), ps(1), rtprio(1), setpriority(2), nice(3), renice(8), p_cansee(9)

AUTHORS


.An -nosplit The original author was
.An Henrik Vestergaard Draboel Aq hvd@terry.ping.dk . This implementation in
.Fx was substantially rewritten by
.An David Greenman . The rtprio_thread system call was implemented by
.An David Xu .
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