Date: Thu, 7 Oct 2004 15:00:35 -0700
From: "David S. Miller" <davem@davemloft.net>
To: Chris Friesen <cfriesen@nortelnetworks.com>
Cc: martijn@entmoot.nl, hzhong@cisco.com, jst1@email.com,
       linux-kernel@vger.kernel.org, alan@lxorguk.ukuu.org.uk,
       davem@redhat.com
Subject: Re: UDP recvmsg blocks after select(), 2.6 bug?
Message-Id: <20041007150035.6e9f0e09.davem@davemloft.net>
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On Thu, 07 Oct 2004 15:49:17 -0600
Chris Friesen <cfriesen@nortelnetworks.com> wrote:

> In this case, select() returns with the socket readable, we call recvmsg() and 
> discover the message is corrupt.  At this point we throw away the corrupt 
> message, so we now have no data waiting to be received.  We return EAGAIN, and 
> userspace goes merrily on its way, handling anything else in its loop, then 
> going back to select().

Incorrect.  When the user specifies blocking on the file descriptor
we must give it what it asked for.  -EAGAIN on a blocking file descriptor
is always a bug, in all situations, that's what this code used to do and we
fixed it because it's a bug.

It goes "merrily on its way" if it marks the file descriptor as non-blocking.
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