Re: [patch] sched: unlocked context-switches

[Ingo Molnar]

* David Mosberger-Tang <David.Mosberger@xxxxxxx> wrote:

>  > The ia64_switch_to() code includes a section that can change a
>  > pinned MMU mapping (when the stack for the new process is in a
>  > different granule from the stack for the old process).  The code
>  > beyond the ".map" label in arch/ia64/kernel/entry.S includes the
>  > comment:
> 
> Also, there was a nasty dead-lock that could trigger if the 
> context-switch was interrupted by a TLB flush IPI.  I don't remember 
> the details offhand, but I'm pretty sure it had to do with 
> switch_mm(), so I suspect it may not be enough to disable irqs just 
> for ia64_switch_to().  Tread with care!

we'll see. The patch certainly needs more testing. Generally we do 
switch_mm()'s outside of the scheduler as well, without disabling 
interrupts.

	Ingo
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