Their first proposed idea was just to change the #ifdef so that for ARM, it
would not attempt to insert any delay at all. That will work, but may not be
optimal (the idea here is to not spin too fast, allow just a bit reduction of
contention on the atomic).
Dan Wexler's solution is to use 'nop' instead of pause. I don't know enough
about the ARM architecture to know if this is any better, but I can't imagine
that it's worse than doing nothing. I suspect this is the superior solution.
Dan, I don't suppose you'd care to contribute back your ARM fixes?
In the redhat link, they also mention using usleep, I think that would be a
very bad idea. The idea is to wait a few cycles; usleep will wait a minimum of
microseconds. Surely that will ruin the performance of the spin locks, making
them no faster than an ordinary blocking mutex.
-- lg
On Mar 23, 2013, at 5:45 PM, Daniel Wexler wrote:
> I used a nop asm instruction to get it to work for me on ARM, though I'm not
> sure if it is any better than their solution.
>
> On Fri, Mar 22, 2013 at 7:28 PM, Richard Shaw <[email protected]> wrote:
> There is an arm specific group within Fedora going through all the
> packages and seeing what will build and what needs fixing. They ran
> into an issue with the "_asm pause" assembler instruction and filed a
> bug[1].
>
> If you have time could you take a look at their proposed fixes and let
> me know if it's a good idea or if there's a better one.
>
> Thanks,
> Richard
>
> [1] https://bugzilla.redhat.com/show_bug.cgi?id=924932
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--
Larry Gritz
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