linux-kernel - Re: [PATCH v2 01/10] usb: host: ehci-sched: refactor scan

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Date:	Sun, 13 Dec 2015 10:29:07 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	"Geyslan G. Bem" <geyslan@...il.com>
cc:	peter.senna@...il.com, <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v2 01/10] usb: host: ehci-sched: refactor scan_isoc
 function

On Sun, 13 Dec 2015, Geyslan G. Bem wrote:

> This patch removes an infinite 'for' loop and makes use of the already
> existing 'restart' tag instead, reducing one leading tab.
> 
> It also puts the easier evaluation (live variable) to be the first in
> two conditionals.
> 
>   if (live && frame == now_frame) { ...
> 
>   if (live && ((frame == now_frame) || ...

You should never do this.  The first test in a conditional should be 
the one that is most likely to cause the expression to fail.  In this 
case, live is almost always true whereas frame == now_frame is true 
only some percentage of the time.  Therefore the frame == now_frame 
test should come first.

Alan Stern

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