On 10/01, Peter Zijlstra wrote:
>
> On Tue, Oct 01, 2013 at 07:01:37PM +0200, Oleg Nesterov wrote:
> > if (exclusive)
> > \
> > __wait.flags = WQ_FLAG_EXCLUSIVE;
> > \
> > else
> > \
> > __wait.flags = 0;
> > \
>
> __wait.flags = exclusive * WQ_FLAG_EXCLUSIVE;
>
> or is that too obscure? ;-)
I do not mind ;) The generated code should be the same.
> > for (;;) {
> > \
> > long intr = prepare_to_wait_event(&wq, &__wait, state);
> > \
>
> int __intr = ...;
>
> The interruptible bit doesn't actually need long;
Yes, it can be even "bool", but see below.
> and local variables
> have __ prefixes in this context.
Yes, yes, will fix.
> > if (condition)
> > \
> > break;
> > \
> >
> > \
> > if (___wait_is_interruptible(state) && intr) {
> > \
> > __ret = intr;
> > \
Since typeof(__ret) == typeof(intr) gcc can (likely) simply do "mov r1, r2",
so "long intr" make the code better.
I am not saying that "int intr" can make it worse, but to me "long" looks
better in this context. But I wouldn't mind to change this.
> > Compiler should optimize out "long intr" if !interruptible/killable.
>
> Yeah, and I think even the if (0 && __intr) would suffice for the unused
> check; otherwise we'd have to adorn the thing with __maybe_unused.
Hmm yes, I didn't see any warning during the compilation, but perhaps
__maybe_unused is needed, thanks.
> > What do you think?
>
> That would actually work I think.. the ___wait_is_interruptible() nicely
> does away with the unused code; the only slightly more expensive thing
> would be the prepare_to_wait_event() thing.
>
> And if that really turns out to be a problem we could even re-use
> ___wait_is_interruptible() to call prepare_to_wait() instead.
OK, thanks.
So I'll wait until your series is applied the resend it officially.
Oleg.
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