Hi Partha / Ying, I will try out the patch and let you know how it goes. I also note about providing the other CPU core dumps - in one of my cases I didn't have them but in others I did but they were interleaved and so were difficult to interpret.
Thanks for getting a patch together so quickly. JT On Wed, Nov 16, 2016 at 10:23 PM, Parthasarathy Bhuvaragan < parthasarathy.bhuvara...@ericsson.com> wrote: > Hi Ying / John, > > The soft lock is the call chain of tipc_nametbl_withdraw(), when it > performs the tipc_conn_kref_release() as it tries to grab nametbl_lock > again while holding it already. > > tipc_nametbl_withdraw > > spin_lock_bh(&tn->nametbl_lock); > > tipc_nametbl_remove_publ > > spin_lock_bh(&seq->lock); > > tipc_nameseq_remove_publ > > tipc_subscrp_report_overlap > > tipc_subscrp_send_event > > tipc_conn_sendmsg > << Here, the (test_bit(CF_CONNECTED, &con->flags)) Fails, leading to the > else case where do do a conn_put() and that triggers the cleanup as > refcount reached 0. Leading the call chain below : >> > tipc_conn_kref_release > tipc_sock_release > tipc_conn_release > tipc_subscrb_delete > tipc_subscrp_delete > tipc_nametbl_unsubscribe > spin_lock_bh(&tn->nametbl_lock); << !! Soft Lockup >> > > One cause is that tipc_exit_net() calls first calls tipc_topsrv_stop() and > then tipc_nametbl_withdraw() in scope of tipc_net_stop(). > > The above chain will only occur in a narrow window for a given connection: > CPU#1: > tipc_nametbl_withdraw() manages to perform tipc_conn_lookup() and steps > the refcount to 2, while in CPU#2 the following occurs: > CPU#2: > tipc_server_stop() calls tipc_close_conn(con). This performs a conn_put() > decrementing refcount to 1. > Now, CPU#1 continues and detects that the connection is not CF_CONNECTED > and does a conn_put(), triggering the release callback. > > Before commit 333f796235a527, the above wont happen. > > /Partha > > > On 11/15/2016 04:11 PM, Xue, Ying wrote: > >> Hi John, >> >> Regarding the stack trace you provided below, I get the two potential >> call chains: >> >> tipc_nametbl_withdraw >> spin_lock_bh(&tn->nametbl_lock); >> tipc_nametbl_remove_publ >> spin_lock_bh(&seq->lock); >> tipc_nameseq_remove_publ >> tipc_subscrp_report_overlap >> tipc_subscrp_send_event >> tipc_conn_sendmsg >> spin_lock_bh(&con->outqueue_lock); >> list_add_tail(&e->list, &con->outqueue); >> >> >> tipc_topsrv_stop >> tipc_server_stop >> tipc_close_conn >> kernel_sock_shutdown >> tipc_subscrb_delete >> spin_lock_bh(&subscriber->lock); >> tipc_nametbl_unsubscribe(sub); >> spin_lock_bh(&tn->nametbl_lock); >> >> Although I suspect this is a revert lock issue leading to the soft >> lockup, I am still unable to understand which lock together with >> nametbl_lock is taken reversely on the two different paths above. >> However, you just gave us the log printed on CPU#2, but the logs >> outputted by other cores are also important. So if possible, please share >> them with us. >> >> By the way, I agree with you, and it seems that commit 333f796235a527 is >> related to the soft lockup. >> >> Regards, >> Ying >> >> -----Original Message----- >> From: John Thompson [mailto:thompa....@gmail.com] >> Sent: Tuesday, November 15, 2016 8:01 AM >> To: tipc-discussion@lists.sourceforge.net >> Subject: [tipc-discussion] v4.7: soft lockup when releasing a socket >> >> Hi, >> >> I am seeing an occasional kernel soft lockup. I have TIPC v4.7 and the >> kernel dump occurs when the system is going down for a reboot. >> >> The kernel dump is: >> >> <0>NMI watchdog: BUG: soft lockup - CPU#2 stuck for 23s! [exfx:1474] >> <6>Modules linked in: tipc jitterentropy_rng echainiv drbg >> platform_driver(O) ipifwd(PO) >> ... >> <6> >> <6>GPR00: c15333e8 a4e0fb80 a4ee3600 a51748ac 00000000 ae475024 a537feec >> fffffffd >> <6>GPR08: a2197408 00000001 00000001 00000004 80691c00 <6>NIP [80691c40] >> _raw_spin_lock_bh+0x40/0x70 <6>LR [c1534f30] >> tipc_nametbl_unsubscribe+0x50/0x120 >> [tipc] <6>Call Trace: >> <6>[a4e0fba0] [c15333e8] tipc_named_reinit+0xf8/0x820 [tipc] >> <6>[a4e0fbb0] [c15336a0] tipc_named_reinit+0x3b0/0x820 [tipc] <6>[a4e0fbd0] >> [c1540bac] tipc_nl_publ_dump+0x50c/0xed0 [tipc] <6>[a4e0fc00] [c154164c] >> tipc_conn_sendmsg+0xdc/0x170 [tipc] <6>[a4e0fc30] [c1533c9c] >> tipc_subscrp_report_overlap+0xbc/0xd0 [tipc] <6>[a4e0fc70] [c153425c] >> tipc_topsrv_stop+0x45c/0x4f0 [tipc] <6>[a4e0fca0] [c1534788] >> tipc_nametbl_remove_publ+0x58/0x110 [tipc] <6>[a4e0fcd0] [c1534c48] >> tipc_nametbl_withdraw+0x68/0x140 [tipc] <6>[a4e0fd00] [c153cc24] >> tipc_nl_node_dump_link+0x1904/0x45d0 [tipc] <6>[a4e0fd30] [c153d838] >> tipc_nl_node_dump_link+0x2518/0x45d0 [tipc] <6>[a4e0fd70] [804f2870] >> sock_release+0x30/0xf0 <6>[a4e0fd80] [804f2944] sock_close+0x14/0x30 >> <6>[a4e0fd90] [80105844] __fput+0x94/0x200 <6>[a4e0fdb0] [8003dca4] >> task_work_run+0xd4/0x100 <6>[a4e0fdd0] [80023620] do_exit+0x280/0x980 >> <6>[a4e0fe10] [80024c48] do_group_exit+0x48/0xb0 <6>[a4e0fe30] [80030344] >> get_signal+0x244/0x4f0 <6>[a4e0fe80] [80007734] do_signal+0x34/0x1c0 >> <6>[a4e0ff30] [800079a8] do_notify_resume+0x68/0x80 <6>[a4e0ff40] >> [8000fa1c] do_user_signal+0x74/0xc4 >> >> >> From the stack dump it looks like tipc_named_reinit is trying to >>> >> acquire nametbl_lock. >> >> From looking at the call chain I can see that tipc_conn_sendmsg can >>> >> send up calling conn_put >> >> which will go on and call the tipc_named_reinit via tipc_sock_release. >> >> As tipc_nametbl_withdraw (from the stack dump) has already acquired the >> nametbl_lock, tipc_named_reinit >> >> cannot get it and so the process hangs. >> >> >> The call to tipc_sock_release (added in Commit 333f796235a527 >> <http://git.atlnz.lc/cgit/cgit.cgi/upstream_imports/linux- >> stable.git/commit/?id=333f796235a52727db7e0a13888045f3aa3d5335>) >> seems to have changed the behaviour >> >> such that it tries to do a lot more when shutting the connection down. >> >> >> If there is other information I can provide please let me know. >> >> Regards, >> >> John >> ------------------------------------------------------------ >> ------------------ >> _______________________________________________ >> tipc-discussion mailing list >> tipc-discussion@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/tipc-discussion >> ------------------------------------------------------------ >> ------------------ >> _______________________________________________ >> tipc-discussion mailing list >> tipc-discussion@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/tipc-discussion >> >> > ------------------------------------------------------------------------------ _______________________________________________ tipc-discussion mailing list tipc-discussion@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/tipc-discussion
