Re: BUG in x86 do_page_fault? [was Re: in_atomic doesn't countlocal_irq_disable?]

[Linus Torvalds]

On Sun, 4 Jan 2004, Pavel Machek wrote:
> > 
> > Please don't do this, it will result in some _really_ nasty problems with 
> > X and other programs that potentially disable interrupts in user
> > space.
> 
> If user program causes page fault with interrupts disabled, it is
> certainly buggy, right?

No.

It may do a best-effort thing. It may also do a best-_performance_ thing, 
in leaving interrupts disabled over a piece of code that doesn't care, 
knowing that disabling interrupts is expensive.  Or it may just be a 
simple case of simplicity: disable interrupts over the whole region, 
knowing that only a part of it matters.

It by no means is automatically a bug. And it unquestionably _does_ 
happen. We used to warn about it. We stopped.

		Linus
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