netdev - Re: [PATCH] net: unix: non blocking recvmsg() should not return -EINTR

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Message-ID: <1395847524.12610.208.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Wed, 26 Mar 2014 08:25:24 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Rainer Weikusat <rweikusat@...ileactivedefense.com>
Cc:	David Laight <David.Laight@...LAB.COM>,
	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] net: unix: non blocking recvmsg() should not return
 -EINTR

On Wed, 2014-03-26 at 15:13 +0000, Rainer Weikusat wrote:

> (This is from memory) If there's a thread blocked in recv and another
> blocked on the lock and the kernel selects the thread blocked on the lock
> for handling the signal, the signal won't be handled until some data is
> received on the socket, ie, possibly never.

Look at what we do for AF_INET. We handle this the proper way.

If we are 'interrupted' by a signal while sleeping in lock_sock(),
recvmsg() on a non blocking socket, we return -EAGAIN properly, not
-EINTR.

Fact that we potentially sleep to get the socket lock is hidden for the
user, its an implementation detail of the kernel.

We never return -EINTR, as stated in manpage for non blocking sockets.

Only AF_UNIX in recent kernels introduced this API change.


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