| Message ID | 20141119220549.GA26133@midget.suse.cz |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
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> -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
From: Jiri Bohac <jbohac@suse.cz> Date: Wed, 19 Nov 2014 23:05:49 +0100 > 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> Applied. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/ipx/af_ipx.c b/net/ipx/af_ipx.c index a0c7536..d0725d9 100644 --- a/net/ipx/af_ipx.c +++ b/net/ipx/af_ipx.c @@ -1764,6 +1764,7 @@ static int ipx_recvmsg(struct kiocb *iocb, struct socket *sock, struct ipxhdr *ipx = NULL; struct sk_buff *skb; int copied, rc; + bool locked = true; lock_sock(sk); /* put the autobinding in */ @@ -1790,6 +1791,8 @@ static int ipx_recvmsg(struct kiocb *iocb, struct socket *sock, if (sock_flag(sk, SOCK_ZAPPED)) goto out; + release_sock(sk); + locked = false; skb = skb_recv_datagram(sk, flags & ~MSG_DONTWAIT, flags & MSG_DONTWAIT, &rc); if (!skb) { @@ -1825,7 +1828,8 @@ static int ipx_recvmsg(struct kiocb *iocb, struct socket *sock, out_free: skb_free_datagram(sk, skb); out: - release_sock(sk); + if (locked) + release_sock(sk); return rc; }
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>