Re: PostmasterIsAlive() in recovery (non-USE_POST_MASTER_DEATH_SIGNAL builds)

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Heikki Linnakangas <hlinnaka(at)iki(dot)fi>
Cc: Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com>, David Rowley <dgrowleyml(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: PostmasterIsAlive() in recovery (non-USE_POST_MASTER_DEATH_SIGNAL builds)
Date: 2021-06-11 01:18:38
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Heikki Linnakangas <hlinnaka(at)iki(dot)fi> writes:
> On 09/04/2021 07:01, Thomas Munro wrote:
>> This seems to work on Linux, macOS, FreeBSD and OpenBSD (and I assume
>> any other BSD). Can anyone tell me if it works on illumos, AIX or
>> HPUX, and if not, how to fix it or disable the feature gracefully?
>> For now the patch assumes that if you have SIGIO then you can do this;
>> perhaps it should also test for O_ASYNC? Perhaps HPUX has the signal
>> but requires a different incantation with I_SETSIG?

I took a look on HPUX 10.20 (gaur's host):

* SIGIO exists, but signal.h only defines it with
-D_INCLUDE_HPUX_SOURCE which we don't use.

* I found I_SETSIG, but ...

$ grep -r SETSIG /usr/include
/usr/include/sys/stropts.h:#define I_SETSIG _IO('S', 9) /* request SIGPOLL signal on events */

stropts.h seems to be for a feature called "streams", which is
probably nonstandard enough that we don't want to deal with it.

So I think the short answer on this platform is that if you conditionalize
on #ifdef SIGIO then it will just not do it, and we should be fine.

Can't say about HPUX 11.

regards, tom lane

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