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-- Problem Description -- After the install of MRG 2.1 Preview on an HS21xm, we see the following messages in /var/log/boot.log: ROOT:elm9m94:log]> grep chrt boot.log-20111023 Setting kernel thread priorities: chrt: failed to set pid 7's policy: Invalid argument chrt: failed to set pid 9's policy: Invalid argument chrt: failed to set pid 14's policy: Invalid argument chrt: failed to set pid 18's policy: Invalid argument chrt: failed to set pid 22's policy: Invalid argument chrt: failed to set pid 26's policy: Invalid argument chrt: failed to set pid 30's policy: Invalid argument chrt: failed to set pid 34's policy: Invalid argument ROOT:elm9m94:~]> uname -a Linux elm9m94 3.0.6-rt18.35.el6rt.x86_64 #1 SMP PREEMPT RT Thu Oct 13 12:55:23 EDT 2011 x86_64 x86_64 x86_64 GNU/Linux ROOT:elm9m94:~]> cat /etc/*release Red Hat Enterprise Linux Server release 6.1 (Santiago) Red Hat Enterprise Linux Server release 6.1 (Santiago) No changes had been made to /etc/init.d/rtctl or /etc/sysconfig/rtctl or any other file (pristine install). Note that pid 7, 9, 14, ... are all the various migration threads (per-cpu) and are running at SCHED_FIFO, prio 99 from ps output: [migration/0] 7 99 FF [migration/1] 9 99 FF [migration/2] 14 99 FF [migration/3] 18 99 FF [migration/4] 22 99 FF [migration/5] 26 99 FF [migration/6] 30 99 FF [migration/7] 34 99 FF So it might just be that the error msg is due to the fact that the migration threads are already at prio 99 and SCHED_FIFO to start with. Setting the RT scheduler priority or policy to be the same as the current might have the effect of taking the running task off the cpu and putting it to the back of the runqueue for that priority (IIRC??). It's possible chrt just returns an error in that case? Not checked. This might just be chrt handling of that situation, but worth looking into. This is new in MRG 2.1. Was not seen in MRG 2.0 kernels or MRG 1.3 and earlier. Nothing relevant in other logs. Might be confusing for customers. This was discussed with Clark Williams (Red Hat) in today's IBM/RH RT Interlock, and Clark has also reproduced. We're filing bug for tracking purposes.
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. New Contents: Cause: Using an older version of rtctl not for MRG-2.1 and up Consequence: Thread priorities were not properly set. Fix: Update to the current version of rtctl Result: Setting the thread priorities works as expected