Add a /sys/kernel entry to indicate that the kernel is a realtime kernel.
This makes it easier (and faster and cheaper) to determine if you're
running on an RT kernel than parsing the output of uname -v.
We found this when we had a udev rule for detecting IRQ registration
that looked at the output of uname -v, looking for the ' RT ' string.
This rule prevented a 32-core box from booting (or delayed it past the
point we were willing to wait) because it was invoking the rule
repeatedly for each core being brought up.
The following commit has been queued for the Errata:
2e76e55 add /sys/kernel/realtime entry
Technical note added. If any revisions are required, please edit the "Technical Notes" field
accordingly. All revisions will be proofread by the Engineering Content Services team.
Cause: the old method used to assert if the running kernel is realtime enabled or not depended on parsing the output of 'uname -v'.
Consequence: That process, when repeated multiple times could become costly and a source of latencies.
Fix: add a file, created only when the kernel is reatime enabled, in /sys, that is an in-memory filesystem and is cheaper to read.
Result: It is ten times faster to verify if the kernel has RT capabilities or not.
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.