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.
Alan Stern
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