Re: [parisc-linux] rmap: parisc __flush_dcache_page

[James Bottomley <James.Bottomley@steeleye.com>]

On Thu, 2004-04-08 at 11:16, Andrea Arcangeli wrote:
> softirq tasklets would be unsafe too, oh well, if you take it really
> from irq context (irq/softirq/tasklet) then just a spinlock isn't
> enough, it'd need to be an irq safe lock or whatever similar plus you
> must be sure to never generate exceptions triggering the call inside the
> critical section. sounds like we need some per-arch abstraction to cover
> this, we for sure don't want an irq spinlock for this, then we can as
> well leave the semaphore for all archs but parisc.

Erm, well, I think this is a global problem.  All VI archs have to use
the flush_ APIs in cachetlb.txt to ensure coherence.  It's just that
sparc seems to have some nice cache manipulation instructions that
relieve it of the necessity of traversing the mappings.

Why don't we want an irq safe spinlock?  As Hugh said, we'd abstract it
so as to be a nop on PI archs.

James