man rtprio_thread (2): examine or modify realtime or idle priority

Other Alias

rtprio

LIBRARY

Lb libc

SYNOPSIS

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

DESCRIPTION

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

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

For the Fn rtprio system call, the Fa pid argument specifies the process to operate on, 0 for the calling thread. When Fa 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 Fa function argument.

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

The Fa *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 Fn rtprio and Fn rtprio_thread system calls will fail if:

Bq Er EFAULT: The rtp pointer passed to Fn rtprio or Fn rtprio_thread was invalid.
Bq Er EINVAL: The specified Fa prio was out of range.
Bq Er 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.
Bq Er ESRCH: The specified process or thread was not found or visible.

AUTHORS

An -nosplit The original author was An Henrik Vestergaard Draboel Aq [email protected] . This implementation in Fx was substantially rewritten by An David Greenman . The Fn rtprio_thread system call was implemented by An David Xu .