RLIMIT_RTTIME documentation for getrlimit.2

From: Michael Kerrisk
Date: Fri Apr 18 2008 - 11:40:49 EST


Peter,

Below is the draft text that I will add to the getrlimit.2 man page to describe
RLIMIT_RTTIME. Does it look okay to you? (I will add a pointer in
sched_setscheduler.2 to this description in getrlimit.2.)

RLIMIT_RTTIME (Since Linux 2.6.25)
Specifies a limit on the amount of CPU time that a
process scheduled under a real-time scheduling
policy may consume without making a blocking sys-
tem call. For the purpose of this limit, each
time a process makes a blocking system call, the
count of its consumed CPU time is reset to zero.
The CPU time count is not reset if the process
continues trying to use the CPU but is preempted,
its time slice expires, or it calls
sched_yield(2).

Upon reaching the soft limit, the process is sent
a SIGXCPU signal. If the process catches or
ignores this signal and continues consuming CPU
time, then SIGXCPU will be generated once each
second until the hard limit is reached, at which
point the process is sent a SIGKILL signal.

The intended use of this limit is to stop a run-
away real-time process from locking up the system.

Cheers,

Michael

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