BUG [preempt-rt] stapio:4521 task might have lost a preemption check!

[Frank Ch. Eigler]

Kiran <kiran@linux.vnet.ibm.com> writes:

> BUG: stapio:4521 task might have lost a preemption check!
> Call Trace:
> [c0000000e0ba3930] [c0000000000122e8] .show_stack+0x94/0x198 (unreliable)
> [c0000000e0ba39e0] [c000000000012414] .dump_stack+0x28/0x3c
> [c0000000e0ba3a60] [c0000000000a688c] .preempt_enable_no_resched+0x68/0x84
> [c0000000e0ba3ae0] [d0000000017368d0] .enter_be_probe+0x278/0x29c [stap_828d9711d4343f96e62db9359ace031f_8344]
> [...]

>From just looking at the rt code, this error appears to occur if we
call preempt_enable_no_resched() without a corresponding
preempt_disable().  This should not arise for a begin/end probe that
the stack trace suggests your script had.  

You could check out the output of "stap -p3 YOURSCRIPT.stp" to see
whether the preempt calls are matching up properly.  Or you could send
us the script and perhaps the vitals suggested in the wiki/HowToReportBugs.

- FChE