On Wednesday 17 June 2009 6:11:42 pm Mel Flynn wrote: > On Wednesday 17 June 2009 13:17:37 John Baldwin wrote: > > On Wednesday 17 June 2009 3:52:54 pm Mel Flynn wrote: > > > On Wednesday 17 June 2009 04:15:26 John Baldwin wrote: > > > > On Tuesday 16 June 2009 7:01:45 pm Mel Flynn wrote: > > > > > On Tuesday 16 June 2009 11:02:42 John Baldwin wrote: > > > > > > On Tuesday 16 June 2009 1:52:23 pm Mel Flynn wrote: > > > > > > > Hi John, > > > > > > > > > > > > > > On Tuesday 16 June 2009 04:19:57 John Baldwin wrote: > > > > > > > > On Monday 15 June 2009 5:53:05 pm Mel Flynn wrote: > > > > > > > > > PID TID COMM TDNAME KSTACK > > > > > > > > > 4283 100215 kdeinit4 - mi_switch > > > > > > > > > turnstile_wait _mtx_lock_sleep uipc_peeraddr kern_getpeername > > > > > > > > > getpeername syscall Xint0x80_syscall > > > > > > > > > % ps -ww 4283 > > > > > > > > > PID TT STAT TIME COMMAND > > > > > > > > > 4283 ?? T 0:00.38 kdeinit4: kdeinit4: kio_http http > > > > > > > > > local:/tmp/ksocket-mel/klauncherxJ1635.slave-socket > > > > > > > > > local:/tmp/ksocket- mel/plasmayC1653.slave-socket (kdeinit4) > > > > > > > > > > > > > > > > > > %ls -l /tmp/ksocket-mel/ > > > > > > > > > > > > > > > > > > total 2 > > > > > > > > > -rw-rw-r-- 1 mel wheel 62 Jun 14 22:55 KSMserver__0 > > > > > > > > > srw------- 1 mel wheel 0 Jun 14 22:55 kdeinit4__0 > > > > > > > > > srwxrwxr-x 1 mel wheel 0 Jun 14 22:55 > > > > > > > > > klauncherxJ1635.slave-socket > > > > > > > > > > > > > > > > You can use kgdb and the scripts at www.freebsd.org/~jhb/gdb. > > > > > > > > Simply run 'kgdb' as root and do 'lcd /folder/with/scripts' and > > > > > > > > 'source gdb6'. You can then do 'lockchain 4283' to find who > > > > > > > > holds the lock this thread is blocked on and what state they > > > > > > > > are in. > > > > > > > > > > > > > > Looks like a deadlock: > > > > > > > > > > > > > > (kgdb) lockchain 4283 > > > > > > > thread 100215 (pid 4283, kdeinit4) blocked on lock 0xc64374a0 > > > > > > > "unp_mtx" thread 100122 (pid 1635, klauncher) blocked on lock > > > > > > > 0xc6806348 "unp_mtx" thread 100215 (pid 4283, kdeinit4) blocked > > > > > > > on lock 0xc64374a0 "unp_mtx" thread 100122 (pid 1635, klauncher) > > > > blocked > > > > > > > > > on lock 0xc6806348 "unp_mtx" thread 100215 (pid 4283, kdeinit4) > > > > > > > blocked on lock 0xc64374a0 "unp_mtx" thread 100122 (pid 1635, > > > > > > > klauncher) blocked on lock 0xc6806348 "unp_mtx" thread 100215 > > > > > > > (pid 4283, kdeinit4) blocked on lock 0xc64374a0 "unp_mtx" thread > > > > > > > 100122 (pid 1635, klauncher) blocked on lock 0xc6806348 "unp_mtx" > > > > > > > thread 100215 (pid 4283, kdeinit4) blocked on lock 0xc64374a0 > > > > > > > "unp_mtx" thread 100122 (pid 1635, klauncher) blocked on lock > > > > > > > 0xc6806348 "unp_mtx" thread 100215 (pid 4283, kdeinit4) blocked > > > > > > > on lock 0xc64374a0 "unp_mtx" thread 100122 (pid 1635, klauncher) > > > > > > > blocked on lock 0xc6806348 "unp_mtx" thread 100215 (pid 4283, > > > > > > > kdeinit4) blocked on lock 0xc64374a0 "unp_mtx" thread 100122 (pid > > > > > > > 1635, klauncher) blocked on lock 0xc6806348 "unp_mtx" thread > > > > > > > 100215 (pid 4283, kdeinit4) blocked on lock 0xc64374a0 "unp_mtx" > > > > > > > thread 100122 (pid 1635, klauncher) blocked on lock 0xc6806348 > > > > > > > "unp_mtx" thread 100215 (pid 4283, kdeinit4) blocked on lock > > > > > > > 0xc64374a0 "unp_mtx" thread 100122 (pid 1635, klauncher) blocked > > > > > > > on lock 0xc6806348 "unp_mtx" thread 100215 (pid 4283, kdeinit4) > > > > > > > blocked on lock 0xc64374a0 "unp_mtx" thread 100122 (pid 1635, > > > > > > > klauncher) blocked on lock 0xc6806348 "unp_mtx" DEADLOCK > > > > > > > > > > > > > > Looking through the scripts now to see how I can get more info on > > > > the > > > > > > > > > call chain and hoping I don't panic the machine ;). It is quite > > > > > > > random to reproduce. > > > > > > > > > > > > In kgdb you can simply do 'tid 100122' followed by 'bt' and 'tid > > > > > > 100215' followed by 'bt'. > > > > > > > > > > Cool, thanks for helping John. Of course it pretty much shows me what > > > > > procstat -k shows and can't get any info on the userland part, but I > > > > > can fully inspect the locks and threads. > > > > > > > > > > Both threads are in TDS_INHIBITED state, and blocked on: > > > > > (kgdb) frame 0 > > > > > #0 sched_switch (td=0xc5971240, newtd=0xc4d39900, flags=259) > > > > > at /usr/src/sys/kern/sched_ule.c:1864 > > > > > 1864 cpuid = PCPU_GET(cpuid); > > > > > > > > That doesn't really tell us anything except that it isn't running. We > > > > know > > > > > > it is actually blocked on a lock, and we need the full stack trace to > > > > see where the two threads were trying to acquire the locks, hence 'bt'. > > > > ' procstat -k' output would be fine, too. > > > > > > the respective bt's: > > > (kgdb) tid 100122 > > > at /usr/src/sys/kern/kern_mutex.c:447 > > > #4 0xc06a68a5 in uipc_peeraddr (so=0xc64309a8, nam=0xe79a2c70) > > > at /usr/src/sys/kern/uipc_usrreq.c:682 > > > #5 0xc06a1e71 in kern_getpeername (td=0xc56e8900, fd=12, sa=0xe79a2c70, > > > alen=0xe79a2c6c) > > > at /usr/src/sys/kern/uipc_syscalls.c:1566 > > > > > > (kgdb) tid 100215 > > > (kgdb) bt > > > at /usr/src/sys/kern/kern_mutex.c:447 > > > #4 0xc06a68a5 in uipc_peeraddr (so=0xc6976338, nam=0xe9ae9c70) > > > at /usr/src/sys/kern/uipc_usrreq.c:682 > > > #5 0xc06a1e71 in kern_getpeername (td=0xc5971240, fd=7, sa=0xe9ae9c70, > > > alen=0xe9ae9c6c) > > > at /usr/src/sys/kern/uipc_syscalls.c:1566 > > > > These are the key frames. It looks like uipc_peeraddr() tries to lock two > > unp locks w/o any protection from the global unp linkage lock. I've > > changed it to use the same locking as uipc_accept() where it first grabs a > > read lock on the linkage lock and then just locks the other end of the > > connection to copy out its sockaddr. > > Thanks John. I'll recompile the kernel with patch and up-to-date current and > report back if there are any side effects or if the bug resurfaces. > Is there a sure way (i.e. testcase) that would expose this condition? At > present, all I can do is wait and maybe play with network interface link > up/down, as it seems to be related from a high level view.
It looks like two ends of a PF_LOCAL socket doing getpeername() at the same time would provoke this. I can maybe write a test program today to provoke this and test it locally. -- John Baldwin _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "freebsd-hackers-unsubscr...@freebsd.org"
