netdev - Re: recvmmsg() timeout behavior strangeness

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Message-ID: <50EDF01E.10709@genband.com>
Date:	Wed, 09 Jan 2013 16:33:02 -0600
From:	Chris Friesen <chris.friesen@...band.com>
To:	Michael Kerrisk <mtk.manpages@...il.com>
CC:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Caitlin Bestler <caitlin.bestler@...il.com>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	Chris Van Hoof <vanhoof@...hat.com>,
	Clark Williams <williams@...hat.com>,
	Neil Horman <nhorman@...driver.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Andrew Grover <andy.grover@...il.com>,
	Elie De Brauwer <eliedebrauwer@...il.com>,
	linux-man@...r.kernel.org, Steven Whitehouse <steve@...gwyn.com>,
	Rémi Denis-Courmont 
	<remi.denis-courmont@...ia.com>
Subject: Re: recvmmsg() timeout behavior strangeness

On 12/23/2012 02:50 PM, Michael Kerrisk wrote:

> If I understand correctly, the *intended* purpose of the timeout
> argument is to set a limit on how long to wait for additional
> datagrams after the arrival of an initial datagram. However, the
> syscall behaves in quite a different way. Instead, it potentially
> blocks forever, regardless of the timeout.

Looking at the code, I think you're correct.

The comments for a2e2725 say the timeout works like for ppoll(), where 
it is "an upper limit on the time for which poll() will block, in 
milliseconds."

I wonder if we could play some games with sk->sk_rcvtimeo to accomplish 
this?

Chris
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