https://github.com/torvalds/linux
Revision 01462405f0c093b2f8dfddafcadcda6c9e4c5cdf authored by Jiri Bohac on 19 November 2014, 22:05:49 UTC, committed by David S. Miller on 21 November 2014, 03:57:03 UTC
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>
Signed-off-by: David S. Miller <davem@davemloft.net>
1 parent d3052bb
History
Tip revision: 01462405f0c093b2f8dfddafcadcda6c9e4c5cdf authored by Jiri Bohac on 19 November 2014, 22:05:49 UTC
ipx: fix locking regression in ipx_sendmsg and ipx_recvmsg
Tip revision: 0146240
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