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Subject: Re: [patch] Real-Time Preemption, -RT-2.6.12-rc1-V0.7.41-07
From: Steven Rostedt <rostedt@goodmis.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: Esben Nielsen <simlo@phys.au.dk>, LKML <linux-kernel@vger.kernel.org>
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Organization: Kihon Technologies
Date: Thu, 31 Mar 2005 07:22:02 -0500
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On Thu, 2005-03-31 at 13:03 +0200, Ingo Molnar wrote:
> * Steven Rostedt <rostedt@goodmis.org> wrote:
> 
> > Well, here it finally is. There's still things I don't like about it. 
> > But it seems to work, and that's the important part.
> > 
> > I had to reluctantly add two items to the task_struct.  I was hoping 
> > to avoid that. But because of race conditions it seemed to be the only 
> > way.
> 
> well it's not a big problem, and we avoided having to add flags to the 
> rt_lock structure, which is the important issue.
> 
> your patch looks good, i've added it to my tree and have uploaded the 
> -26-00 patch. It boots fine on my testbox, except for some new messages:
> 
>  knodemgrd_0/902: BUG in __down_complete at kernel/rt.c:1568
>   [<c0103956>] dump_stack+0x23/0x25 (20)
>   [<c0130dcd>] down_trylock+0x1fb/0x200 (48)
>   [<c0364ee2>] nodemgr_host_thread+0xd0/0x17b (48)
>   [<c0100d4d>] kernel_thread_helper+0x5/0xb (136249364)
>  ---------------------------
>  | preempt count: 00000001 ]
>  | 1-level deep critical section nesting:
>  ----------------------------------------
>  .. [<c0133a75>] .... print_traces+0x1b/0x52
>  .....[<c0103956>] ..   ( <= dump_stack+0x23/0x25)
> 
> this goes away if i revert your patch. It seems the reason is that 
> trylock hasnt been updated to use the pending-owner logic?

Hmm, The pending owner logic in __down_trylock uses the grab_lock
function. It doesn't need the capture_lock since it never sleeps. I'm
downloading your 42-00-experimental now and installing it to see if I
can get the same message. Did you try the patch against 41-11? Maybe the
patch didn't go in so smoothly.

Anyway, I'll take a look at it now and let you know what I find.

Thanks,

-- Steve


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