netdev - RE: [PATCH] Check for SKBTX_HW

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Date:   Tue, 12 Mar 2019 23:07:49 +0000
From:   "Keller, Jacob E" <jacob.e.keller@...el.com>
To:     Paul Thomas <pthomas8589@...il.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH] Check for SKBTX_HW_TSTAMP in macb driver



> -----Original Message-----
> From: Paul Thomas [mailto:pthomas8589@...il.com]
> Sent: Tuesday, March 12, 2019 3:05 PM
> To: Keller, Jacob E <jacob.e.keller@...el.com>
> Cc: netdev@...r.kernel.org
> Subject: Re: [PATCH] Check for SKBTX_HW_TSTAMP in macb driver
> 
> Hi Jake, thanks for all the help and for looking at this!
> 
> >
> > You have two conditionals inside, and I misread where you were doing the checking
> of the SKBTX_HW_TSTAMP flag.
> >
> > I would do the following :
> >
> > if (unlikely(skb_shinfo(skb)->tx_flags & SKBTX_HWTSTAMP) &&
> >     gem_ptp_do_txstamp(queue, skb, desc)) {
> I guess I was thinking the call to gem_ptp_do_txstamp() could be
> avoided in many cases, but either way is fine with me..

The call will be avoided by virtue of short-curcuit boolean AND. If the first check is false, then the entire section is skipped without evaluating the second condition.

Thanks,
Jake

> >   ....
> > }
> >
> -Paul