From: Arnd Bergmann <arnd@arndb.de>
To: Jiri Bohac <jbohac@suse.cz>
Cc: David Miller <davem@davemloft.net>,
acme@ghostprotocols.net, netdev@vger.kernel.org
Subject: Re: [PATCH v4] ipx: fix locking regression in ipx_sendmsg and ipx_recvmsg
Date: Wed, 19 Nov 2014 23:12:21 +0100 [thread overview]
Message-ID: <3682315.1qi3iAkNAF@wuerfel> (raw)
In-Reply-To: <20141119220549.GA26133@midget.suse.cz>
On Wednesday 19 November 2014 23:05:49 Jiri Bohac wrote:
> This fixes an old regression introduced by commit
> b0d0d915 (ipx: remove the BKL).
>
> When a recvmsg syscall blocks waiting for new data, no data can be sent on the
> same socket with sendmsg because ipx_recvmsg() sleeps with the socket locked.
>
> This breaks mars-nwe (NetWare emulator):
> - the ncpserv process reads the request using recvmsg
> - ncpserv forks and spawns nwconn
> - ncpserv calls a (blocking) recvmsg and waits for new requests
> - nwconn deadlocks in sendmsg on the same socket
>
> Commit b0d0d915 has simply replaced BKL locking with
> lock_sock/release_sock. Unlike now, BKL got unlocked while
> sleeping, so a blocking recvmsg did not block a concurrent
> sendmsg.
>
> Only keep the socket locked while actually working with the socket data and
> release it prior to calling skb_recv_datagram().
>
>
> Signed-off-by: Jiri Bohac <jbohac@suse.cz>
>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
next prev parent reply other threads:[~2014-11-19 22:12 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-17 1:34 ipx: fix locking regression in ipx_sendmsg and ipx_recvmsg Jiri Bohac
2014-11-18 13:37 ` Arnd Bergmann
2014-11-18 20:49 ` David Miller
2014-11-18 22:10 ` Jiri Bohac
2014-11-18 22:24 ` [PATCH v2] " Jiri Bohac
2014-11-19 8:32 ` Arnd Bergmann
2014-11-19 10:34 ` Jiri Bohac
2014-11-19 10:38 ` [PATCH v3] " Jiri Bohac
2014-11-19 10:50 ` Arnd Bergmann
2014-11-19 14:38 ` Sergei Shtylyov
2014-11-19 20:44 ` David Miller
2014-11-19 22:05 ` [PATCH v4] ipx: " Jiri Bohac
2014-11-19 22:12 ` Arnd Bergmann [this message]
2014-11-21 19:46 ` David Miller
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