On Tue, Jul 10, 2012 at 10:24:07AM -0400, Alan Stern wrote:
> On Tue, 10 Jul 2012, Richard Zhao wrote:
>
> > > > @@ -4037,6 +4038,13 @@ static void hub_port_connect_change(struct usb_hub *hub, int port1,
> > > > }
> > > > }
> > > >
> > > > + if (unlikely(hcd->phy && !hdev->parent)) {
> > >
> > > Why is this "unlikely"? And why mark it as such, is this a "fast path"
> > > that needs the compiler to know this hint to optimize things here?
> > >
> > > Please don't use likely() or unlikely() except in places it really is
> > > needed, _and_ you have measured the difference. Have you done so in
> > > this place?
> > It's from a comment by Alan Stern.
> > http://www.spinics.net/lists/linux-usb/msg64987.html
>
> That comment was made in a somewhat different context. At the time
> the code was part of an interrupt handler; now it isn't.
>
> > Actually, for my board, it's not unlikely. But for others which don't
> > have notify_connect/disconnect, it's unlikely.
> >
> > Because it's not unlikely for all boards, I prefer remove "unlikely".
>
> It's no longer a big deal one way or another. I don't care about the
> "unlikely" because it's on a cold path running in process context. Go
> ahead and remove it.
Ok. I'll remove it.
Thanks
Richard
>
> Alan Stern
>
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