Linux-kernel mailing list archive 1998-10,: Re: semaphore => spinlock in {get|put}name

# Re: semaphore => spinlock in {get|put}name

Jakub Jelinek (jj@sunsite.ms.mff.cuni.cz)
Mon, 9 Mar 1998 15:24:55 +0100 (MET)

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>
> Jakub Jelinek <jj@sunsite.ms.mff.cuni.cz> writes:
>
> > Hi!
> >
> > Is there any reason why do we use an expensive semaphore instead of a cheap
> > spinlock?
>
> I think the reason is that get_free_page(GFP_KERNEL) may sleep, also a spin
> lock is a nop on UP (and UP needs it too because of the sleep).

But what I did in the patch was to move get_free_page out of the guarded
area... Once we find out we need to get_free_page, we won't touch any shared
variable, so we don't need to stay protected by the semaphore/spinlock...

Cheers,
Jakub
___________________________________________________________________
Jakub Jelinek | jj@sunsite.mff.cuni.cz | http://sunsite.mff.cuni.cz
Administrator of SunSITE Czech Republic, MFF, Charles University
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Ultralinux - first 64bit OS to take full power of the UltraSparc
Linux version 2.1.89 on a sparc64 machine (498.80 BogoMips).
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