rtprio.2 (2010 09)

rtprio(2) rtprio(2)

RETURN VALUE

rtprio() returns the following values:

0 to 127 The process was a real-time process. The value is the process’s former (before

the call) real-time priority.

RTPRIO_RTOFF The process was not a real-time process.

-1 An error occurred. errno is set to indicate the error.

ERRORS

rtprio() fails, errno is set to one of the following values:

[EACCES] The target process could not be accessed due to compartmental restrictions.

[EINVAL] prio is not

RTPRIO_NOCHG, RTPRIO_RTOFF, or in the range 0 to 127.

[EPERM] The calling process is not a user having appropriate privileges, and neither its real

nor effective user ID match the real or saved user ID of the process indicated by

pid.

[EPERM] The group access list of the calling process does not contain a group having

PRIV_RTPRIO capability and prio is not RTPRIO_NOCHG,or

RTPRIO_RTOFF

with a pid of zero.

[ESRCH] No process can be found corresponding to that speciﬁed by pid .

EXAMPLES

The following call to

rtprio() sets the calling process to a real-time priority of 90:

rtprio(0, 90);

WARNINGS

Normally, compute-bound programs should not be run at real-time priorities, because all timesharing

work on the CPU would come to a complete halt.

DEPENDENCIES

Because processes executing at real-time priorities get scheduling preference over a system process exe-

cuting at a lower priority, unexpected system behavior can occur after a power failure on systems that

support power-fail recovery. For example, when

init (see init(1M)) receives the powerfail signal

SIGPWR, it normally reloads programmable hardware such as terminal multiplexers. If a higher-priority

real-time process is eligible to run after the power failure, the running of init is delayed. This condition

temporarily prevents terminal input to any process, including real-time shells of higher priority than the

eligible real-time process. To avoid this situation, a real-time process should catch SIGPWR and suspend

itself until init has ﬁnished its powerfail processing.

AUTHOR

rtprio() was developed by HP.