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SubjectRe: + down_write-preserve-local-irqs.patch added to -mm tree
On Wed, 20 Dec 2006 11:54:23 +0100
Arjan van de Ven <arjan@infradead.org> wrote:

> On Wed, 2006-12-20 at 02:38 -0800, akpm@osdl.org wrote:
> > The patch titled
> > down_write(): preserve local irqs
> > has been added to the -mm tree. Its filename is
> > down_write-preserve-local-irqs.patch
> >
> > See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
> > out what to do about this
> >
> > ------------------------------------------------------
> > Subject: down_write(): preserve local irqs
>
> excuse me? Am I missing something here?

Lots.

> down_write() is a sleeping function, right? what business does it have
> to be *ever* called with irqs off?
>
> if the answer is "none whatsoever", what good is saving irq state then?
>

a) this patch is for testers to confirm that this fixes the hangs

b) there's plenty of precendent for this - powerpc won't boot if
mutex_lock() enables interrupts, for example. We just assume that
during early boot these sleeping locks aren't contended.

yes, it does suck.
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