Re: SegFault on 9.6.14 - Mailing list pgsql-hackers

Thomas Munro <thomas.munro@gmail.com> writes:

> On Wed, Jul 17, 2019 at 11:33 AM Jerry Sievers <gsievers19@comcast.net> wrote:
>
>>          ->  Nested Loop Left Join  (cost=251621.81..12300177.37 rows=48 width=44)
>>                ->  Gather  (cost=1001.55..270403.27 rows=48 width=40)
>
>>                ->  Limit  (cost=250620.25..250620.27 rows=1 width=20)
>
>>                                        ->  Gather  (cost=1000.00..250452.00 rows=3706 width=4)
>
> One observation is that it's a rescan a bit like the one in the
> unsuccessful repro attempt I posted, but it has *two* Gather nodes in
> it (and thus two parallel query DSM segments), and only one of them
> should be rescanned, and from the backtrace we see that it is indeed
> the expected one, the one under the Limit operator.  Neither of them
> should be getting unmapped in the leader though and AFAIK nothing
> happening in the workers could cause this effect, the leader would
> have to explicitly unmap the thing AFAIK.
>
> On Wed, Jul 17, 2019 at 11:42 AM Jerry Sievers <gsievers19@comcast.net> wrote:
>> mmap(NULL, 287624, PROT_READ|PROT_WRITE, MAP_SHARED, 124, 0) = 0x7f3d011f2000
>> mmap(NULL, 262504, PROT_READ|PROT_WRITE, MAP_SHARED, 124, 0) = 0x7f3d011b1000
>> munmap(0x7f3d011b1000, 262504)          = 0
>
> Ok, there go our two parallel query DSM segments, and there it is
> being unmapped.  Hmm.  Any chance you could attach a debugger, and
> "break munmap", "cont", and then show us the backtrace "bt" when that
> is reached?

gdb /usr/lib/postgresql/9.6/bin/postgres 21640
GNU gdb (Ubuntu 7.11.1-0ubuntu1~16.5) 7.11.1
Copyright (C) 2016 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from /usr/lib/postgresql/9.6/bin/postgres...Reading symbols from
/usr/lib/debug/.build-id/04/6f55a5ce6ce05064edfc8feee61c6cb039d296.debug...done.
done.
Attaching to program: /usr/lib/postgresql/9.6/bin/postgres, process 21640
Reading symbols from /usr/lib/x86_64-linux-gnu/libxml2.so.2...Reading symbols from
/usr/lib/debug/.build-id/d3/57ce1dba1fab803eddf48922123ffd0a303676.debug...done.
done.
Reading symbols from /lib/x86_64-linux-gnu/libpam.so.0...(no debugging symbols found)...done.
Reading symbols from /lib/x86_64-linux-gnu/libssl.so.1.0.0...Reading symbols from
/usr/lib/debug/.build-id/ff/69ea60ebe05f2dd689d2b26fc85a73e5fbc3a0.debug...done.
done.
Reading symbols from /lib/x86_64-linux-gnu/libcrypto.so.1.0.0...Reading symbols from
/usr/lib/debug/.build-id/15/ffeb43278726b025f020862bf51302822a40ec.debug...done.
done.
Reading symbols from /usr/lib/x86_64-linux-gnu/libgssapi_krb5.so.2...(no debugging symbols found)...done.
Reading symbols from /lib/x86_64-linux-gnu/librt.so.1...Reading symbols from
/usr/lib/debug//lib/x86_64-linux-gnu/librt-2.23.so...done.
done.
Reading symbols from /lib/x86_64-linux-gnu/libdl.so.2...Reading symbols from
/usr/lib/debug//lib/x86_64-linux-gnu/libdl-2.23.so...done.
done.
Reading symbols from /lib/x86_64-linux-gnu/libm.so.6...Reading symbols from
/usr/lib/debug//lib/x86_64-linux-gnu/libm-2.23.so...done.
done.
Reading symbols from /usr/lib/x86_64-linux-gnu/libldap_r-2.4.so.2...Reading symbols from
/usr/lib/debug/.build-id/38/90d33727391e4a85dc0f819ab0aa29bb5dfc86.debug...done.
done.
Reading symbols from /lib/x86_64-linux-gnu/libsystemd.so.0...(no debugging symbols found)...done.
Reading symbols from /lib/x86_64-linux-gnu/libc.so.6...Reading symbols from
/usr/lib/debug//lib/x86_64-linux-gnu/libc-2.23.so...done.
done.
Reading symbols from /usr/lib/x86_64-linux-gnu/libicuuc.so.55...Reading symbols from
/usr/lib/debug/.build-id/46/3d8b610702d64ae0803c7dfcaa02cfb4c6477b.debug...done.
done.
Reading symbols from /lib/x86_64-linux-gnu/libz.so.1...Reading symbols from
/usr/lib/debug/.build-id/8d/9bd4ce26e45ef16075c67d5f5eeafd8b562832.debug...done.
done.
Reading symbols from /lib/x86_64-linux-gnu/liblzma.so.5...(no debugging symbols found)...done.
Reading symbols from /lib/x86_64-linux-gnu/libaudit.so.1...(no debugging symbols found)...done.
Reading symbols from /usr/lib/x86_64-linux-gnu/libkrb5.so.3...(no debugging symbols found)...done.
Reading symbols from /usr/lib/x86_64-linux-gnu/libk5crypto.so.3...(no debugging symbols found)...done.
Reading symbols from /lib/x86_64-linux-gnu/libcom_err.so.2...Reading symbols from
/usr/lib/debug//lib/x86_64-linux-gnu/libcom_err.so.2.1...done.
done.
Reading symbols from /usr/lib/x86_64-linux-gnu/libkrb5support.so.0...(no debugging symbols found)...done.
Reading symbols from /lib/x86_64-linux-gnu/libpthread.so.0...Reading symbols from
/usr/lib/debug/.build-id/b1/7c21299099640a6d863e423d99265824e7bb16.debug...done.
done.
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Reading symbols from /lib64/ld-linux-x86-64.so.2...Reading symbols from
/usr/lib/debug//lib/x86_64-linux-gnu/ld-2.23.so...done.
done.
Reading symbols from /usr/lib/x86_64-linux-gnu/liblber-2.4.so.2...Reading symbols from
/usr/lib/debug/.build-id/8e/613d0b8d8e3537785637424782be8502ababd2.debug...done.
done.
Reading symbols from /lib/x86_64-linux-gnu/libresolv.so.2...Reading symbols from
/usr/lib/debug//lib/x86_64-linux-gnu/libresolv-2.23.so...done.
done.
Reading symbols from /usr/lib/x86_64-linux-gnu/libsasl2.so.2...(no debugging symbols found)...done.
Reading symbols from /usr/lib/x86_64-linux-gnu/libgssapi.so.3...(no debugging symbols found)...done.
Reading symbols from /usr/lib/x86_64-linux-gnu/libgnutls.so.30...(no debugging symbols found)...done.
Reading symbols from /lib/x86_64-linux-gnu/libselinux.so.1...(no debugging symbols found)...done.
Reading symbols from /lib/x86_64-linux-gnu/libgcrypt.so.20...(no debugging symbols found)...done.
Reading symbols from /usr/lib/x86_64-linux-gnu/libicudata.so.55...(no debugging symbols found)...done.
Reading symbols from /usr/lib/x86_64-linux-gnu/libstdc++.so.6...(no debugging symbols found)...done.
Reading symbols from /lib/x86_64-linux-gnu/libgcc_s.so.1...Reading symbols from
/usr/lib/debug//lib/x86_64-linux-gnu/libgcc_s.so.1...done.
done.
Reading symbols from /lib/x86_64-linux-gnu/libkeyutils.so.1...(no debugging symbols found)...done.
Reading symbols from /usr/lib/x86_64-linux-gnu/libheimntlm.so.0...(no debugging symbols found)...done.
Reading symbols from /usr/lib/x86_64-linux-gnu/libkrb5.so.26...(no debugging symbols found)...done.
Reading symbols from /usr/lib/x86_64-linux-gnu/libasn1.so.8...(no debugging symbols found)...done.
Reading symbols from /usr/lib/x86_64-linux-gnu/libhcrypto.so.4...(no debugging symbols found)...done.
Reading symbols from /usr/lib/x86_64-linux-gnu/libroken.so.18...(no debugging symbols found)...done.
Reading symbols from /usr/lib/x86_64-linux-gnu/libp11-kit.so.0...(no debugging symbols found)...done.
Reading symbols from /usr/lib/x86_64-linux-gnu/libidn.so.11...(no debugging symbols found)...done.
Reading symbols from /usr/lib/x86_64-linux-gnu/libtasn1.so.6...(no debugging symbols found)...done.
Reading symbols from /usr/lib/x86_64-linux-gnu/libnettle.so.6...(no debugging symbols found)...done.
Reading symbols from /usr/lib/x86_64-linux-gnu/libhogweed.so.4...(no debugging symbols found)...done.
Reading symbols from /usr/lib/x86_64-linux-gnu/libgmp.so.10...(no debugging symbols found)...done.
Reading symbols from /lib/x86_64-linux-gnu/libpcre.so.3...Reading symbols from
/usr/lib/debug//lib/x86_64-linux-gnu/libpcre.so.3.13.2...done.
done.
Reading symbols from /lib/x86_64-linux-gnu/libgpg-error.so.0...(no debugging symbols found)...done.
Reading symbols from /usr/lib/x86_64-linux-gnu/libwind.so.0...(no debugging symbols found)...done.
Reading symbols from /usr/lib/x86_64-linux-gnu/libheimbase.so.1...(no debugging symbols found)...done.
Reading symbols from /usr/lib/x86_64-linux-gnu/libhx509.so.5...(no debugging symbols found)...done.
Reading symbols from /usr/lib/x86_64-linux-gnu/libsqlite3.so.0...Reading symbols from
/usr/lib/debug/.build-id/3b/0454e57467057071f7ad49651e0fa7b01cf5c7.debug...done.
done.
Reading symbols from /lib/x86_64-linux-gnu/libcrypt.so.1...Reading symbols from
/usr/lib/debug//lib/x86_64-linux-gnu/libcrypt-2.23.so...done.
done.
Reading symbols from /usr/lib/x86_64-linux-gnu/libffi.so.6...Reading symbols from
/usr/lib/debug/.build-id/9d/9c958f1f4894afef6aecd90d1c430ea29ac34f.debug...done.
done.
Reading symbols from /usr/lib/postgresql/9.6/lib/auto_explain.so...Reading symbols from
/usr/lib/debug/.build-id/94/ab76178c50b0e098f2bd0f3501d9cb6562c743.debug...done.
done.
Reading symbols from /usr/lib/postgresql/9.6/lib/pg_stat_statements.so...Reading symbols from
/usr/lib/debug/.build-id/cf/f288800c22fd97059aaf8e425ae17e29fb88fb.debug...done.
done.
Reading symbols from /usr/lib/postgresql/9.6/lib/pglogical.so...(no debugging symbols found)...done.
Reading symbols from /usr/lib/x86_64-linux-gnu/libpq.so.5...(no debugging symbols found)...done.
Reading symbols from /lib/x86_64-linux-gnu/libnss_files.so.2...Reading symbols from
/usr/lib/debug//lib/x86_64-linux-gnu/libnss_files-2.23.so...done.
done.
0x00007f3d093379f3 in __epoll_wait_nocancel () at ../sysdeps/unix/syscall-template.S:84
84    ../sysdeps/unix/syscall-template.S: No such file or directory.
(gdb) break munmap
Breakpoint 1 at 0x7f3d09331740: file ../sysdeps/unix/syscall-template.S, line 84.
(gdb) cont
Continuing.

Program received signal SIGUSR1, User defined signal 1.
hash_search_with_hash_value (hashp=0x5566701baa68, keyPtr=keyPtr@entry=0x7ffc37be9790, 
    hashvalue=hashvalue@entry=1634369601, action=action@entry=HASH_FIND, 
    foundPtr=foundPtr@entry=0x0)
    at /build/postgresql-9.6-5O8OLM/postgresql-9.6-9.6.14/build/../src/backend/utils/hash/dynahash.c:959
959    /build/postgresql-9.6-5O8OLM/postgresql-9.6-9.6.14/build/../src/backend/utils/hash/dynahash.c: No such file or
directory.
(gdb) bt
#0  hash_search_with_hash_value (hashp=0x5566701baa68, keyPtr=keyPtr@entry=0x7ffc37be9790, 
    hashvalue=hashvalue@entry=1634369601, action=action@entry=HASH_FIND, 
    foundPtr=foundPtr@entry=0x0)
    at /build/postgresql-9.6-5O8OLM/postgresql-9.6-9.6.14/build/../src/backend/utils/hash/dynahash.c:959
#1  0x000055666e1224ca in BufTableLookup (tagPtr=tagPtr@entry=0x7ffc37be9790, 
    hashcode=hashcode@entry=1634369601)
    at /build/postgresql-9.6-5O8OLM/postgresql-9.6-9.6.14/build/../src/backend/storage/buffer/buf_table.c:96
#2  0x000055666e12527d in BufferAlloc (foundPtr=0x7ffc37be978b "", strategy=0x556670360418, 
    blockNum=53, forkNum=MAIN_FORKNUM, relpersistence=112 'p', smgr=0x5566702a5990)
    at /build/postgresql-9.6-5O8OLM/postgresql-9.6-9.6.14/build/../src/backend/storage/buffer/bufmgr.c:1013
#3  ReadBuffer_common (smgr=0x5566702a5990, relpersistence=<optimized out>, 
    forkNum=forkNum@entry=MAIN_FORKNUM, blockNum=blockNum@entry=53, mode=RBM_NORMAL, 
    strategy=0x556670360418, hit=0x7ffc37be9837 "")
    at /build/postgresql-9.6-5O8OLM/postgresql-9.6-9.6.14/build/../src/backend/storage/buffer/bufmgr.c:745
#4  0x000055666e125b15 in ReadBufferExtended (reln=0x7f3d015e2670, 
    forkNum=forkNum@entry=MAIN_FORKNUM, blockNum=blockNum@entry=53, 
    mode=mode@entry=RBM_NORMAL, strategy=<optimized out>)
    at /build/postgresql-9.6-5O8OLM/postgresql-9.6-9.6.14/build/../src/backend/storage/buffer/bufmgr.c:664
#5  0x000055666defc036 in heapgetpage (scan=scan@entry=0x5566703484f8, page=page@entry=53)
    at /build/postgresql-9.6-5O8OLM/postgresql-9.6-9.6.14/build/../src/backend/access/heap/heapam.c:375
#6  0x000055666defd5c2 in heapgettup_pagemode (key=0x0, nkeys=0, dir=ForwardScanDirection, 
    scan=0x5566703484f8)
    at /build/postgresql-9.6-5O8OLM/postgresql-9.6-9.6.14/build/../src/backend/access/heap/heapam.c:1036
#7  heap_getnext (scan=scan@entry=0x5566703484f8, 
    direction=direction@entry=ForwardScanDirection)
    at /build/postgresql-9.6-5O8OLM/postgresql-9.6-9.6.14/build/../src/backend/access/heap/heapam.c:1787
#8  0x000055666e053e21 in SeqNext (node=node@entry=0x556670328c48)
    at /build/postgresql-9.6-5O8OLM/postgresql-9.6-9.6.14/build/../src/backend/executor/nodeSeqscan.c:80
#9  0x000055666e03d711 in ExecScanFetch (recheckMtd=0x55666e053de0 <SeqRecheck>, 
    accessMtd=0x55666e053df0 <SeqNext>, node=0x556670328c48)
    at /build/postgresql-9.6-5O8OLM/postgresql-9.6-9.6.14/build/../src/backend/executor/execScan.c:95
#10 ExecScan (node=node@entry=0x556670328c48, 
    accessMtd=accessMtd@entry=0x55666e053df0 <SeqNext>, 
    recheckMtd=recheckMtd@entry=0x55666e053de0 <SeqRecheck>)
    at /build/postgresql-9.6-5O8OLM/postgresql-9.6-9.6.14/build/../src/backend/executor/execScan.c:180
#11 0x000055666e053ea8 in ExecSeqScan (node=node@entry=0x556670328c48)
    at /build/postgresql-9.6-5O8OLM/postgresql-9.6-9.6.14/build/../src/backend/executor/nodeSeqscan.c:127
---Type <return> to continue, or q <return> to quit---


>
>
>
>
> --
> Thomas Munro
> https://enterprisedb.com
>
>
>

-- 
Jerry Sievers
Postgres DBA/Development Consulting
e: postgres.consulting@comcast.net