Messages in this thread | | | Date | Tue, 4 Apr 2006 14:00:03 +0200 | From | Ingo Molnar <> | Subject | Re: 2.6.16-rt10 |
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* Simon Derr <Simon.Derr@bull.net> wrote:
> On Tue, 28 Mar 2006, Ingo Molnar wrote: > > > > > * Simon Derr <simon.derr@bull.net> wrote: > > > > > On Mon, 27 Mar 2006, Ingo Molnar wrote: > > > > > > > i've released -rt10 > > > > > > Is anyone working on a port of this patch to the IA64 architecture ? > > > > not that i know of. If someone wants to do that, take a look at the > > x86_64 changes (or ppc/mips/i386 changes) to get an idea. These are the > > rough steps needed: > > [snip] > > > Work in progress... (based on -rt11) > So far I have a kernel that almost boots, but not quite. > > First issue: 'BUG: udev:45 task might have lost a preemption check!' > > When looking at the code in preempt_enable_no_resched(), why is the > value of preempt_count() checked to be non-zero _after_ calling > dec_preempt_count() ? > > I saw several posts on this list claiming that this message is > harmless, but I'd like to figure what's going on.
the warning means that doing a preempt_enable_no_resched() while being in a preemptible section is most likely a bug, and that you could lose a need_resched() check. (and introduce a scheduling latency) What's the backtrace? This could be the sign of a not fully/correctly converted arch/*/kernel/process.c (but i'm only guessing here).
> My boot process is stuck later when insmod loads the driver for the > MPT Fusion SCSI adapter. It's waiting for a second interrupt to > arrive, and that never happens. > > I see that the -rt patch touches many drivers by changing calls to > local_irq_save (and friends), changing the type of the semaphores, but > the MPT driver makes no use of these. > > Any ideas ?
you should first check the PREEMPT_NONE kernel with PREEMPT_SOFTIRQS and PREEMPT_HARDIRQS enabled. I.e. first check whether IRQ threading works. Then enable all the other PREEMPT options one by one: PREEMPT_DESKTOP, PREEMPT_RCU, PREEMPT_BKL. Only when all these work switch to PREEMPT_RT.
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