Re: [PATCH v9 REBASE 6/9] USB: notify phy when root hub port connect change

On Tue, Jul 10, 2012 at 10:24:07AM -0400, Alan Stern wrote:

On Tue, 10 Jul 2012, Richard Zhao wrote:

quoted

quoted

quoted

@@ -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.

quoted

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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