Re: lockdep splat with 3.2-rc2-rt3+

From: Yong Zhang
Date: Wed Nov 30 2011 - 03:33:37 EST


On Thu, Nov 24, 2011 at 11:50:06PM +0100, John Kacur wrote:
> So, as a little experiment, on v3.2.0-rc2-rt3
> I redefined MAX_LOCKDEP_ENTRIES from 16384UL to 32768UL
>
> Then from /proc/lockdep_stats
>
> I got
> direct dependencies: 18026 [max: 32768]
>
> The fact that 18026 is only a little larger than the normal max (by 1642)
> to me is another indication that, this is not a case of something in
> lockdep going out of control that needs to be fixed, but just another
> indication that in some circumstances it would be legitimate to raise
> the value.

Yeah, seems the reason is in RT we have no dedicated softirq-context
anymore, IOW, both process-context and softirq-context are taken as
process-context. That will increase the usage of lockdep entries
because we expand the scope of process-context.

Thanks,
Yong
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