[pgpool-general: 9116] Re: Another segmentation fault

[Tatsuo Ishii]

Hi,

> Hi,
> 
> For the first backtrace (in protocol/child.c:1076), it tries to access slot
> 2, which is null:
> (gdb) info locals
> frontend_auth_cxt = 0x55803d0ff040 <errordata+192>
> oldContext = 0x55803eacd070
> save_exception_stack = 0x7ffc8cdd0fb0
> save_context_stack = 0x0
> local_sigjmp_buf = {{__jmpbuf = {0, -4847230081711116359, 0,
> 140722671836608, 94009268320888, 140437064355872, -4847230081734185031,
> -1710719621514694727}, __mask_was_saved = 0, __saved_mask = {__val =
> {12884901889, 94009295947704, 94009295947728, 0, 140722671782208,
> 94009266127820, 60129542144, 140722671782336,
>         94009266128191, 0, 0, 94009266967008, 60129543624, 140722671782304,
> 94009265945097, 94009266967017}}}}
> backend = 0x7fba0c407168
> topmem_sp = 0x7fba0c4037a0
> topmem_sp_set = 1 '\001'
> i = 2
> 
> (gdb) p *backend
> $5 = {
>   info = 0x7fba04272c08,
>   slots = {0x7fba0c403a00, 0x7fba0c403a30, 0x0 <repeats 126 times>}
> }
> (gdb) p *backend->slots[0]
> $6 = {
>   sp = 0x7fba0c4037a0,
>   pid = 574235237,
>   key = 1951614039,
>   con = 0x7fba0c406548,
>   closetime = 0
> }
> (gdb) p *backend->slots[1]
> $7 = {
>   sp = 0x7fba0c4037a0,
>   pid = 21,
>   key = 1024,
>   con = 0x7fba0c40b9a8,
>   closetime = 0
> }
> (gdb) p *backend->slots[2]
> Cannot access memory at address 0x0

Thank you for the info.  This is really weird. By the time when the
execution reach here, backend->slots[2] must be filled like slot[0]
and slot[1] since VALID_BACKEND(2) returns true which means the
connection to backend 2 is valid. I need more time to investigate
this.

> For the second crash (in pool_connection_pool.c:326), all slots are null:
> (gdb) info locals
> i = 0
> freed = 0
> closetime = 0
> oldestp = 0x7f474f36e168
> ret = 0x0
> info = 0x55b511283469 <opt_sort>
> p = 0x7f474f36e168
> 
> (gdb) p *p
> $7 = {
>   info = 0x7f47470d5c08,
>   slots = {0x0 <repeats 128 times>}
> }
> 
> (gdb) p p->slots[0]
> $10 = (POOL_CONNECTION_POOL_SLOT *) 0x0
> (gdb) p p->slots[1]
> $11 = (POOL_CONNECTION_POOL_SLOT *) 0x0
> (gdb) p p->slots[2]
> $12 = (POOL_CONNECTION_POOL_SLOT *) 0x0

This is strange too. How come p->slots[0-2] is 0 if VALID_BACKEND
returns true. I will look into this.

> I hope this helps.
> 
> Best regards,
> Emond
> 
> Op di 4 jun 2024 om 04:56 schreef Tatsuo Ishii <ishii at sraoss.co.jp>:
> 
>> > No worries. I hope you had a good trip. Last night we triggered the last
>> > crash again. Is there anything we can do to make it easier for you to
>> find
>> > the cause?
>>
>> It would be helpful if you could share some variable values in the
>> core file. Since I don't have the pgpool load module when you got the
>> core, I cannot inspect the variables using the core you provided.
>>
>> > #0  connect_backend (sp=0x55803eb0a6b8, frontend=0x55803eb08768) at
>> > protocol/child.c:1076
>> > #1  0x000055803ce3d02a in get_backend_connection
>> (frontend=0x55803eb08768)
>> > at protocol/child.c:2112
>> > #2  0x000055803ce38fd5 in do_child (fds=0x55803eabea90) at
>> > protocol/child.c:416
>> > #3  0x000055803cdfea4c in fork_a_child (fds=0x55803eabea90, id=13) at
>> > main/pgpool_main.c:863
>> > #4  0x000055803cdfde30 in PgpoolMain (discard_status=0 '\000',
>> > clear_memcache_oidmaps=0 '\000') at main/pgpool_main.c:561
>> > #5  0x000055803cdfb9e6 in main (argc=2, argv=0x7ffc8cdddda8) at
>> > main/main.c:365
>>
>> Around protocol/child.c:1076:
>>                                 /* set DB node id */
>>                                 pool_set_db_node_id(CONNECTION(backend,
>> i), i);
>>
>> I want to see the values in the "backend" struct. Since CONNECTION
>> macro is used here, you have to do something like in a gdb session.
>>
>> p *backend->slots[0]
>> p *backend->slots[1]
>> p *backend->slots[2]
>>
>> Best reagards,
>> --
>> Tatsuo Ishii
>> SRA OSS LLC
>> English: http://www.sraoss.co.jp/index_en/
>> Japanese:http://www.sraoss.co.jp
>>