[PATCH] Convert powerpc simple spinlocks into ticket locks
Torsten Duwe
duwe at lst.de
Fri Feb 7 22:49:49 EST 2014
On Fri, Feb 07, 2014 at 11:45:30AM +0100, Peter Zijlstra wrote:
>
> That might need to be lhz too, I'm confused on all the load variants.
;-)
> > unlock:
> > lhz %0, 0, &tail
> > addic %0, %0, 1
No carry with this one, I'd say.
Besides, unlock increments the head.
> > lwsync
> > sth %0, 0, &tail
> >
Given the beauty and simplicity of this, may I ask Ingo:
you signed off 314cdbefd1fd0a7acf3780e9628465b77ea6a836;
can you explain why head and tail must live on the same cache
line? Or is it just a space saver? I just ported it to ppc,
I didn't think about alternatives.
What about
atomic_t tail;
volatile int head; ?
Admittedly, that's usually 8 bytes instead of 4...
Torsten
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