From mboxrd@z Thu Jan 1 00:00:00 1970 From: Isaac Huang Date: Tue, 17 Mar 2009 17:17:28 -0400 Subject: [Lustre-devel] Deadlock in usocklnd In-Reply-To: <49BFFF1C.8080203@psc.edu> References: <49BFFF1C.8080203@psc.edu> Message-ID: <20090317211728.GV17185@sun.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lustre-devel@lists.lustre.org On Tue, Mar 17, 2009 at 03:50:52PM -0400, Paul Nowoczynski wrote: > Hi, > I've got some code which uses ptlrpc and lnet and a few weeks ago we > integrated usocklnd into our environment. This lnd has been working > quite well and seems very efficient. The only issue so far is that we're > hitting a clear case of deadlock when trying to handle a failed > connection. I'm not sure if this code is actually in use by any lustre > component as of yet but I thought it best to bring this to your attention. > paul The usocklnd was completely rewritten some time ago, and the new code hasn't been used at any Lustre major site as far as I know. It appeared to me that you were using the new usocklnd. It seemed to me that the deadlock had been triggered like: 1. usocklnd_poll_thread -> usocklnd_process_stale_list -> usocklnd_tear_peer_conn: acquired &peer->up_lock. 2. Then with &peer->up_lock locked, usocklnd_tear_peer_conn -> usocklnd_destroy_txlist -> usocklnd_destroy_tx -> lnet_finalize -> lnet_complete_msg_locked -> lnet_return_credits_locked -> lnet_post_send_locked -> lnet_ni_send -> usocklnd_send -> usocklnd_find_or_create_conn 3. And usocklnd_find_or_create_conn would try to acquire the same &peer->up_lock again. I'm not 100% certain about the sequence above, but generally it should be considered unsafe for a LND to call into LNet with a LND lock held since LNet would likely call back into the LND again. Paul, please file a bug and assign it to lustre-spider-team at sun.com directly. Thanks, Isaac > (gdb) bt > #0 0x00002b3872336888 in __lll_mutex_lock_wait () from > /lib64/libpthread.so.0 > #1 0x00002b38723328a5 in _L_mutex_lock_107 () from /lib64/libpthread.so.0 > #2 0x00002b3872332333 in pthread_mutex_lock () from /lib64/libpthread.so.0 > #3 0x000000000049c9f5 in usocklnd_find_or_create_conn (peer=0x2695270, > type=0, connp=0x42803d30, tx=0x2aaad46f5d10, zc_ack=0x0, > send_immediately=0x42803d2c) at > ..//../..//lnet-lite/ulnds/socklnd/conn.c:841 > #4 0x00000000004a2701 in usocklnd_send (ni=0x25e1810, private=0x0, > lntmsg=0x2aaacca1ace0) at > ..//../..//lnet-lite/ulnds/socklnd/usocklnd_cb.c:124 > #5 0x000000000048d886 in lnet_ni_send (ni=0x25e1810, msg=0x2aaacca1ace0) > at ..//../..//lnet-lite/lnet/lib-move.c:863 > #6 0x000000000048dd20 in lnet_post_send_locked (msg=0x2aaacca1ace0, > do_send=1) at ..//../..//lnet-lite/lnet/lib-move.c:951 > #7 0x000000000048dfb4 in lnet_return_credits_locked (msg=0x2aaacca1ae40) > at ..//../..//lnet-lite/lnet/lib-move.c:1108 > #8 0x0000000000494230 in lnet_complete_msg_locked (msg=0x2aaacca1ae40) > at ..//../..//lnet-lite/lnet/lib-msg.c:143 > #9 0x00000000004944f5 in lnet_finalize (ni=0x25e1810, > msg=0x2aaacca1ae40, status=-5) at ..//../..//lnet-lite/lnet/lib-msg.c:242 > #10 0x000000000049bff8 in usocklnd_destroy_tx (ni=0x25e1810, > tx=0x26950c0) at ..//../..//lnet-lite/ulnds/socklnd/conn.c:562 > #11 0x000000000049c02d in usocklnd_destroy_txlist (ni=0x25e1810, > txlist=0x2693650) at ..//../..//lnet-lite/ulnds/socklnd/conn.c:574 > #12 0x000000000049b09c in usocklnd_tear_peer_conn (conn=0x2692550) at > ..//../..//lnet-lite/ulnds/socklnd/conn.c:148 > #13 0x000000000049f5c8 in usocklnd_process_stale_list > (pt_data=0x25e1c98) at ..//../..//lnet-lite/ulnds/socklnd/poll.c:112 > #14 0x000000000049f7b2 in usocklnd_poll_thread (arg=0x25e1c98) at > ..//../..//lnet-lite/ulnds/socklnd/poll.c:169 > #15 0x0000000000450871 in psc_usklndthr_begin (arg=0x25e4370) at > ..//../..//psc_fsutil_libs/psc_util/usklndthr.c:16 > #16 0x000000000044f000 in _pscthr_begin (arg=0x7fff389980b0) at > ..//../..//psc_fsutil_libs/psc_util/thread.c:237 > #17 0x00002b38723302f7 in start_thread () from /lib64/libpthread.so.0 > #18 0x00002b387281fe3d in clone () from /lib64/libc.so.6 > (gdb) up > #4 0x00000000004a2701 in usocklnd_send (ni=0x25e1810, private=0x0, > lntmsg=0x2aaacca1ace0) at > ..//../..//lnet-lite/ulnds/socklnd/usocklnd_cb.c:124 > 124 rc = usocklnd_find_or_create_conn(peer, type, &conn, tx, NULL, > (gdb) print *peer > $4 = {up_list = {next = 0x6e1b08, prev = 0x6e1b08}, up_peerid = {nid = > 562954416842067, pid = 2147520945}, up_conns = {0x2692550, 0x0, 0x0}, > up_ni = 0x25e1810, up_incarnation = 0, up_incrn_is_set = 0, up_refcount > = {counter = 3}, up_lock = {__data = {__lock = 2, __count = 0, __owner = > 23283, > __nusers = 1, __kind = 0, __spins = 0, __list = {__prev = 0x0, __next = > 0x0}}, > __size = "\002\000\000\000\000\000\000\000???Z\000\000\001", '\0' 26 times>, __align = 2}, up_errored = 0, up_last_alive = 0} > (gdb) > > ## We're waiting for a lock which we already hold! > * 6 Thread 1115703616 (LWP 23283) 0x00002b3872336888 in > __lll_mutex_lock_wait () from /lib64/libpthread.so.0 > > _______________________________________________ > Lustre-devel mailing list > Lustre-devel at lists.lustre.org > http://lists.lustre.org/mailman/listinfo/lustre-devel