Re: [HACKERS] How to handle waitingForLock in LockWaitCancel()

[Hiroshi Inoue]

Tom Lane wrote: > > Hiroshi Inoue <[EMAIL PROTECTED]> writes: > > I sometimes encountered SEGV errors in my test case > > when I canceled the execution. > > Can you provide backtraces from these SEGVs? > ISTM the backtrace isn't sufficient to figure out how the error occured. As far as I see the error was caused by other backends which terimnated safely with the similar sequence of signals. I have a (about 7MB) postmaster log with the trace_locks option on. I could send it to you if you want. Note that I applied the following patch to debug my suspicion. In addition I added an SegvException Handler to postgres.c. diff -c -r1.35 proc.c *** storage/lmgr/proc.c 2001/01/29 10:00:58 1.35 --- storage/lmgr/proc.c 2001/03/05 07:56:56 *************** *** 327,332 **** --- 327,334 ---- if (!waitingForLock) return false; + if (MyProc->links.next != INVALID_OFFSET) + fprintf(stderr, "LockWaitCancel pid=%d must RemoveFromWaitQueue\n", MyProc->pid); waitingForLock = false; /* Turn off the deadlock timer, if it's still running (see ProcSleep) */ And the backtrace is as follows. #0 0x40130db7 in __libc_pause () #1 0x811981c in SegvExceptionHandler (postgres_signal_arg=11) at postgres.c:966 #2 <signal handler called> #3 0x8482 in ?? () #4 0x811547e in ProcLockWakeup (lockMethodTable=0x8204260, lock=0x409d6bdc) at proc.c:771 #5 0x8114500 in LockReleaseAll (lockmethod=1, proc=0x409d9d20, allxids=1 '\001', xid=0) at lock.c:1438 #6 0x81150b4 in ProcKill () at proc.c:446 #7 0x810df3b in shmem_exit (code=0) at ipc.c:187 #8 0x810dead in proc_exit (code=0) at ipc.c:146 #9 0x815891e in elog (lev=1, fmt=0x81aee71 "The system is shutting down") at elog.c:465 #10 0x8119927 in ProcessInterrupts () at postgres.c:1039 #11 0x810c526 in s_lock (lock=0x40195016 "\001", file=0x81ac4ea "spin.c", line=156) at s_lock.c:140 #12 0x810fec7 in SpinAcquire (lockid=6) at spin.c:156 #13 0x8114f74 in LockWaitCancel () at proc.c:349 #14 0x81197d8 in die (postgres_signal_arg=15) at postgres.c:947 #15 <signal handler called> #16 0x8482 in ?? () #17 0x400ffcd4 in _IO_old_file_xsputn (f=0x81ce3a8, data=0xbfffc288, n=49) at oldfileops.c:294 #18 0x400f1acf in buffered_vfprintf (s=0x81ce3a8, format=0x81adba0 "LockWaitCancel pid=%d must RemoveFromWaitQueue\n", args=0xbfffe8c8) at vfprintf.c:1767 #19 0x400ed5cc in _IO_vfprintf (s=0x81ce3a8, format=0x81adba0 "LockWaitCancel pid=%d must RemoveFromWaitQueue\n", ap=0xbfffe8c8) at vfprintf.c:1029 #20 0x400f4f03 in fprintf (stream=0x81ce3a8, format=0x81adba0 "LockWaitCancel pid=%d must RemoveFromWaitQueue\n") at fprintf.c:32 #21 0x8114f25 in LockWaitCancel () at proc.c:331 #22 0x811988c in QueryCancelHandler (postgres_signal_arg=2) at postgres.c:993 #23 <signal handler called> #24 0x8482 in ?? () #25 0x810e22b in IpcSemaphoreLock (semId=32768, sem=8, interruptOK=1 '\001') at ipc.c:423 #26 0x811530f in ProcSleep (lockMethodTable=0x8204260, lockmode=4, lock=0x409d726c, holder=0x409d7e08) at proc.c:669 #27 0x8112eb3 in WaitOnLock (lockmethod=1, lockmode=4, lock=0x409d726c, holder=0x409d7e08) at lock.c:995 #28 0x81124d8 in LockAcquire (lockmethod=1, locktag=0xbfffeb5c, xid=373273, lockmode=4) at lock.c:779 #29 0x8111372 in XactLockTableWait (xid=373282) at lmgr.c:309 #30 0x80cf5ef in EvalPlanQual (estate=0x8260a0c, rti=1, tid=0xbfffebe0) at execMain.c:1751 #31 0x80ceebd in ExecReplace (slot=0x8260bec, tupleid=0xbfffec3c, estate=0x8260a0c) at execMain.c:1449 #32 0x80ceb2e in ExecutePlan (estate=0x8260a0c, plan=0x8260964, operation=CMD_UPDATE, numberTuples=0, direction=ForwardScanDirection, destfunc=0x82611c0) at execMain.c:1119 #33 0x80cdf73 in ExecutorRun (queryDesc=0x82609f0, estate=0x8260a0c, feature=3, count=0) at execMain.c:233 #34 0x811ac2b in ProcessQuery (parsetree=0x825379c, plan=0x8260964, dest=Remote) at pquery.c:297 #35 0x811964b in pg_exec_query_string ( query_string=0x8253400 "update branches set bbalance = bbalance + 687 where bid = 1", dest=Remote, parse_context=0x8237640) at postgres.c:810 #36 0x811a712 in PostgresMain (argc=9, argv=0xbfffee9c, real_argc=12, real_argv=0xbffff774, username=0x82104b9 "reindex") at postgres.c:1900 #37 0x80ffb03 in DoBackend (port=0x8210250) at postmaster.c:2080 #38 0x80ff6fa in BackendStartup (port=0x8210250) at postmaster.c:1863 #39 0x80fea96 in ServerLoop () at postmaster.c:963 #40 0x80fe527 in PostmasterMain (argc=12, argv=0xbffff774) at postmaster.c:662 #41 0x80df8e9 in main (argc=12, argv=0xbffff774) at main.c:149 Regards, Hiroshi Inoue ---------------------------(end of broadcast)--------------------------- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly