Re: Preempt Threshold Measurements

[Andrew Morton]

Con Kolivas <kernel@xxxxxxxxxxx> wrote:
>
> Gabriel Devenyi writes:
> 
> > Well I'm not particularly educated in kernel internals yet, here's some 
> > reports from the system when its running.
> > 
> > 6ms non-preemptible critical section violated 4 ms preempt threshold starting 
> > at do_munmap+0xd2/0x140 and ending at do_munmap+0xeb/0x140
> 
> Certainly the do_munmap and exit_mmap seem to be repeat offenders on my 
> machine too (more the latter in my case).
> 

This is a false positive.  Nothing is setting need_resched(), so
unmap_vmas() doesn't bother dropping the lock.

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