netdev - [BUG] TIPC handling of -ERESTARTSYS in connect()

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Message-ID: <503F84CF.208@genband.com>
Date:	Thu, 30 Aug 2012 09:20:47 -0600
From:	Chris Friesen <chris.friesen@...band.com>
To:	netdev <netdev@...r.kernel.org>, ying.xue@...driver.com,
	Allan Stephens <allan.stephens@...driver.com>,
	Jon Maloy <jon.maloy@...csson.com>
Subject: [BUG]  TIPC handling of -ERESTARTSYS in connect()

Hi,

I'm seeing some behaviour that looks unintentional in the TIPC connect() call.
I'm running TIPC 1.7.7.  My userspace code (stripped of error handling) looks
like this:

	int sd = socket (AF_TIPC, SOCK_SEQPACKET,0);
	connect(sd,(struct sockaddr*)&topsrv,sizeof(topsrv));

where topsrv is the address of the TIPC topology server.  The thing that's weird
is that intermittently we get a EISCONN error on the connect call.

Looking at the TIPC connect() code, I think what is happening is that
wait_event_interruptible_timeout() is being interrupted by a signal and returns
-ERESTARTSYS.  This sets sock->state to SS_DISCONNECTING and exits.  Userspace
sees the ERESTARTSYS and retries the syscall, then we hit the
"sock->state != SS_UNCONNECTED" check and exit with -EISCONN.

I think current mainline is susceptible to this as well.

I'm not sure what the proper fix would be--can we detect coming back in that we were
waiting for a message and just skip down to the wait_event_interruptible_timeout()
call?

Chris

-- 

Chris Friesen
Software Designer

3500 Carling Avenue
Ottawa, Ontario K2H 8E9
www.genband.com

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