Re: [PATCH] Fix x86_64 page fault scheduler race

[Mathieu Desnoyers]

* Ingo Molnar (mingo@xxxxxxx) wrote:
> 
> * Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx> wrote:
> 
> > You are right in that x86_64 does not seems to play as safely as 
> > x86_32 on this matter; it uses current->mm. Probably it shouldn't 
> > assume "current" is valid. Actually, I don't see where x86_64 disables 
> > interrupts around __switch_to, so this would seem to be a race 
> > condition. Or have I missed something ?
> 
> the scheduler disables interrupts around __switch_to(). (x86 does not 
> set __ARCH_WANT_INTERRUPTS_ON_CTXSW)
> 
> 	Ingo


Ok, so I guess it's only useful to NMIs then. However, it makes me
wonder why this comment was there in the first place on x86_32
vmalloc_fault() and why it uses read_cr3() :

        * Do _not_ use "current" here. We might be inside
        * an interrupt in the middle of a task switch..

Mathieu

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Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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