Re: src/test/recovery regression failure on bionic

Hi,

On 2020-01-08 17:31:06 -0500, Tom Lane wrote:
> (1) d20703805's test will clearly fall over if there are more than six
> FDs open in the postmaster when set_max_safe_fds is called, because it
> sets max_files_per_process = 26 while set_max_safe_fds requires at
> least 20 usable FDs to be available.

> (4) NetBSD 7.0's cron leaves three extra open FDs in processes that
> it spawns.  I have not looked into why, but I have experimentally
> observed this.  For example, lsof on a "sleep" launched from cron
> shows
> 
> COMMAND  PID USER   FD   TYPE             DEVICE SIZE/OFF    NODE NAME
> sleep   7824  tgl  cwd   VDIR                0,0      512  795201 /home/tgl
> sleep   7824  tgl  txt   VREG                0,0    10431 1613152 /bin/sleep
> sleep   7824  tgl  txt   VREG                0,0  1616564   22726 /lib/libc.so.12.193.1
> sleep   7824  tgl  txt   VREG                0,0    55295   22747 /lib/libgcc_s.so.1.0
> sleep   7824  tgl  txt   VREG                0,0   187183   22762 /lib/libm.so.0.11
> sleep   7824  tgl  txt   VREG                0,0    92195 1499524 /libexec/ld.elf_so
> sleep   7824  tgl    0r  PIPE 0xfffffe803131eb58    16384         
> sleep   7824  tgl    1w  PIPE 0xfffffe8007ec4a30        0         ->0xfffffe800cc0d2c0
> sleep   7824  tgl    2w  PIPE 0xfffffe8007ec4a30        0         ->0xfffffe800cc0d2c0
> sleep   7824  tgl    7u                                           unknown file system type: 0
> sleep   7824  tgl    8u                                           unknown file system type: 0
> sleep   7824  tgl    9w  PIPE 0xfffffe80036c4dc0        0         
> 
> while of course "sleep" launched by hand has only 0/1/2 open.

Is it worth having the test close superflous FDs? It'd not be hard to do
so via brute force (or even going through /proc/self/fd).

Greetings,

Andres Freund