Date: Sat, 20 Feb 2010 11:27:21 +0000 (UTC) From: "Bjoern A. Zeeb" <bzeeb-lists@lists.zabbadoz.net> To: Mikolaj Golub <to.my.trociny@gmail.com> Cc: freebsd-net@freebsd.org Subject: Re: mpd has hung Message-ID: <20100220112639.L27327@maildrop.int.zabbadoz.net> In-Reply-To: <86bpflqr5b.fsf@zhuzha.ua1> References: <20100217132632.GA756@crete.org.ua> <4B7D5D95.20007@gmx.com> <86bpflqr5b.fsf@zhuzha.ua1>
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On Fri, 19 Feb 2010, Mikolaj Golub wrote: > On Thu, 18 Feb 2010 17:32:37 +0200 Nikos Vassiliadis wrote: > >> On 2/17/2010 3:26 PM, Alexander Shikoff wrote: >>> Hello All, >>> >>> I have mpd 5.3 running on 8.0-RC1 as PPPoE server (now only 5 clients). >>> Today mpd process hung and I cannot kill it with -9 signal, and I cannot >>> access it's console via telnet. >>> >>> State of process in `top` output is STOP: >>> 73551 root 2 44 0 29588K 5692K STOP 6 0:32 0.00% mpd5 >>> >>> # procstat -kk 73551 >>> PID TID COMM TDNAME KSTACK >>> 73551 100233 mpd5 - mi_switch+0x16f sleepq_wait+0x42 _cv_wait+0x111 flowtable_flush+0x51 if_detach+0x2f2 ng_iface_shutdown+0x1e ng_rmnode+0x167 ng_apply_item+0xef7 ng_snd_item+0x2ce ngc_send+0x1d2 sosend_generic+0x3f6 kern_sendit+0x13d sendit+0xdc sendto+0x4d syscall+0x1da Xfast_syscall+0xe1 >>> 73551 100502 mpd5 - mi_switch+0x16f thread_suspend_switch+0xc6 thread_single+0x1b6 exit1+0x72 sigexit+0x7c postsig+0x306 ast+0x279 doreti_ast+0x1f >>> >>> Is there a way to stop a process without rebooting a whole system? >>> Thanks in advance! >>> >>> P.S. I'm ready for experiments with it before tonight, but I cannot >>> force system to crash in order to get crash dump right now. >>> >> >> It's probably too late now, but are you sure that nobody pressed >> CTLR-Z while in the mpd console??? >> >> CTLR-Z will send SIGSTOP to the process and the process will >> stop. While stopped, all processing stops(including receiving >> SIGKILL, you cannot kill it, and the signals are queued). You >> have to send SIGCONT for the process to continue. > > We were discussing this problem with Alexander in another (Russian/Ukrainian > speaking) maillist. And it looks like the problem is the following. > > mpd5 thread was detaching ng interface and when doing flowtable_flush() it > slept in cv_wait waiting for flowclean_cycles variable to be updated. It > should have been awaken by flowcleaner thread but this thread got stuck in > endless loop, supposedly in flowtable_clean_vnet()/flowtable_free_stale(), I > think because of inconsistent state of some lists (iface?) due to if_detach > being in progress. I have patches that are out for review. -- Bjoern A. Zeeb It will not break if you know what you are doing.
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