From: Stephen Hemminger <shemminger@vyatta.com>
To: David Miller <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Subject: Re: [PATCH] tcp_probe: avoid modulus operation and wrap fix
Date: Mon, 25 Jan 2010 08:30:06 -0800 [thread overview]
Message-ID: <20100125083006.47fd2f7e@nehalam> (raw)
In-Reply-To: <20100124.224122.13742906.davem@davemloft.net>
On Sun, 24 Jan 2010 22:41:22 -0800 (PST)
David Miller <davem@davemloft.net> wrote:
> From: Stephen Hemminger <shemminger@vyatta.com>
> Date: Sun, 24 Jan 2010 21:50:01 -0800
>
> > @@ -75,12 +75,12 @@ static struct {
> >
> > static inline int tcp_probe_used(void)
> > {
> > - return (tcp_probe.head - tcp_probe.tail) % bufsize;
> > + return (tcp_probe.head - tcp_probe.tail) & (bufsize - 1);
> > }
> >
> > static inline int tcp_probe_avail(void)
> > {
> > - return bufsize - tcp_probe_used();
> > + return bufsize - tcp_probe_used() - 1;
> > }
> >
> > /*
>
> Hmmm... When the ring is full head==tail, which means
> tcp_probe_used() returns 0. Which would now make tcp_probe_avail()
> return "bufsize - 0 - 1".
>
> Is that right?
Yes. in this ring; empty is head == tail, and full needs to
be tail == head - 1.
--
next prev parent reply other threads:[~2010-01-25 16:30 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-25 5:50 [PATCH] tcp_probe: avoid modulus operation and wrap fix Stephen Hemminger
2010-01-25 6:41 ` David Miller
2010-01-25 16:30 ` Stephen Hemminger [this message]
2010-01-25 23:48 ` David Miller
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