Re: BUG #13657: Some kind of undetected deadlock between query and "startup process" on replica.

>
>
> So wal replay got AccessExclusiveLock on relation 17987 and waiting for
> something.
> And query waiting for AccessShareLock on the same relation.
>
>
=E2=80=8Bgdb backtrace from stuck startup process:

(gdb) bt
#0  0x00007f04ad862633 in select () from /lib/x86_64-linux-gnu/libc.so.6
#1  0x00007f04af86488e in pg_usleep (microsec=3D<optimized out>) at
/tmp/buildd/postgresql-9.4-9.4.4/build/../src/port/pgsleep.c:53
#2  0x00007f04af7328ac in WaitExceedsMaxStandbyDelay () at
/tmp/buildd/postgresql-9.4-9.4.4/build/../src/backend/storage/ipc/standby.c=
:171
#3  ResolveRecoveryConflictWithVirtualXIDs
(reason=3DPROCSIG_RECOVERY_CONFLICT_SNAPSHOT, waitlist=3D0x7f04b13ba2f0) at
/tmp/buildd/postgresql-9.4-9.4.4/build/../src/backend/storage/ipc/standby.c=
:232
#4  ResolveRecoveryConflictWithVirtualXIDs (waitlist=3D0x7f04b13ba2f0,
reason=3DPROCSIG_RECOVERY_CONFLICT_SNAPSHOT) at
/tmp/buildd/postgresql-9.4-9.4.4/build/../src/backend/storage/ipc/standby.c=
:191
#5  0x00007f04af544445 in heap_xlog_clean (record=3D0x7f04b1395b80,
lsn=3D107351881751648) at
/tmp/buildd/postgresql-9.4-9.4.4/build/../src/backend/access/heap/heapam.c:=
7329
#6  heap2_redo (lsn=3D107351881751648, record=3D0x7f04b1395b80) at
/tmp/buildd/postgresql-9.4-9.4.4/build/../src/backend/access/heap/heapam.c:=
8488
#7  0x00007f04af580648 in StartupXLOG () at
/tmp/buildd/postgresql-9.4-9.4.4/build/../src/backend/access/transam/xlog.c=
:6920
#8  0x00007f04af6f5d8f in StartupProcessMain () at
/tmp/buildd/postgresql-9.4-9.4.4/build/../src/backend/postmaster/startup.c:=
224
#9  0x00007f04af58c579 in AuxiliaryProcessMain (argc=3D2, argv=3D<optimized
out>) at
/tmp/buildd/postgresql-9.4-9.4.4/build/../src/backend/bootstrap/bootstrap.c=
:422
#10 0x00007f04af6f235b in StartChildProcess (type=3DStartupProcess) at
/tmp/buildd/postgresql-9.4-9.4.4/build/../src/backend/postmaster/postmaster=
.c:5155
#11 0x00007f04af6f4847 in PostmasterMain (argc=3D<optimized out>,
argv=3D<optimized out>) at
/tmp/buildd/postgresql-9.4-9.4.4/build/../src/backend/postmaster/postmaster=
.c:1237
#12 0x00007f04af513a5d in main (argc=3D5, argv=3D0x7f04b13731a0) at
/tmp/buildd/postgresql-9.4-9.4.4/build/../src/backend/main/main.c:228
=E2=80=8B



--=20
Maxim Boguk
Senior Postgresql DBA
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>

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