Copyright (c) 1994, Henrik Vestergaard Draboel
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Copyright (c) 2011 Xin LI <delphij@FreeBSD.org>
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modification, are permitted provided that the following conditions
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documentation and/or other materials provided with the distribution.
THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.
.Dd December 8, 2021 .Dt RTPRIO 2 .Os .Sh NAME .Nm rtprio , .Nm rtprio_thread .Nd examine or modify realtime or idle priority .Sh LIBRARY .Lb libc .Sh SYNOPSIS n sys/types.h n 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" .Sh 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.
p The .Fa function argument specifies the operation to be performed. RTP_LOOKUP to lookup the current priority, and RTP_SET to set the priority.
p 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.
p For the .Fn rtprio_thread system call, the .Fa lwpid specifies the thread to operate on, 0 for the calling thread.
p 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: d -literal struct rtprio { u_short type; u_short prio; }; .Ed
p The value of the .Va 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 .Va prio field ranges between 0 and .Dv RTP_PRIO_MAX
q usually 31 . 0 is the highest possible priority.
p Realtime and idle priority is inherited through .Fn fork and .Fn exec .
p 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. .Sh RETURN VALUES .Rv -std rtprio rtprio_thread .Sh ERRORS The .Fn rtprio and .Fn rtprio_thread system calls will fail if: l -tag -width Er t Bq Er EFAULT The rtp pointer passed to .Fn rtprio or .Fn rtprio_thread was invalid. t Bq Er EINVAL The specified .Fa prio was out of range. t Bq Er EPERM The calling thread is not allowed to set the priority. Only root is allowed to change the realtime or idle priority of any thread. Exceptional privileges can be granted through the .Xr mac_priority 4 policy and the realtime and idletime user groups. The .Xr sysctl 8 variable .Va security.bsd.unprivileged_idprio is deprecated. If set to non-zero, it lets any user change the idle priority of threads they own. t Bq Er ESRCH The specified process or thread was not found or visible. .El .Sh SEE ALSO .Xr nice 1 , .Xr ps 1 , .Xr rtprio 1 , .Xr setpriority 2 , .Xr nice 3 , .Xr mac_priority 4 , .Xr renice 8 , .Xr p_cansee 9 .Sh AUTHORS .An -nosplit The original author was .An Henrik Vestergaard Draboel Aq Mt hvd@terry.ping.dk . This implementation in .Fx was substantially rewritten by .An David Greenman . The .Fn rtprio_thread system call was implemented by .An David Xu .