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

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Message-ID: <504085D9.3010907@windriver.com>
Date:	Fri, 31 Aug 2012 17:37:29 +0800
From:	Ying Xue <ying.xue@...driver.com>
To:	Chris Friesen <chris.friesen@...band.com>
CC:	netdev <netdev@...r.kernel.org>,
	Allan Stephens <allan.stephens@...driver.com>,
	Jon Maloy <jon.maloy@...csson.com>
Subject: Re: [BUG]  TIPC handling of -ERESTARTSYS in connect()

Hi Chris,

Although this is a known issue, still thanks for your report.

Regardless of 1.7.7 or mainline, the issue really exists.
Can you please check and verify the attached patch?

PS: the patch is based on 1.7.7 rather than mainline.

Thanks,
Ying

Chris Friesen wrote:
> 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
>
>
>   


View attachment "0001-tipc-correctly-handle-ERESTARTSYS-return-value-of-co.patch" of type "text/x-diff" (3843 bytes)