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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Daniel Gustafsson <dgustafsson@postgresql.org>
Cc: Andres Freund <andres@anarazel.de>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Cc: Rahila Syed <rahilasyed90@gmail.com>
Subject: Re: pgsql: Add function to get memory context stats for processes
Date: Wed, 23 Apr 2025 14:14:34 -0400
Message-ID: <1428549.1745432074@sss.pgh.pa.us> (raw)
In-Reply-To: <CA+Tgmob1HFe-EbDmLs-xoQQfWAj8aB_cPToW-OOfhs4mFLfizg@mail.gmail.com>
References: <E1u24yn-003Ggy-01@gemulon.postgresql.org>
	<CA+Tgmoaey-kOP1k5FaUnQFd1fR0majVebWcL8ogfLbG_nt-Ytg@mail.gmail.com>
	<zppwd3scfznxhptdwm765l73wttegi5mibaxyxdwihlmzg3khs@fdhzkq3uxyct>
	<CA+Tgmob7yyONbdv-DRRrWxQPL9AsXFxzs3OH1F6vxSc14prLFA@mail.gmail.com>
	<rkbjmh4fipn5wzf4kqnge3p2szvhd7kgxgccoho5dtntojmkvt@uppvdxpywiba>
	<CA+TgmoZgOwiF1auY+wxUBC+7GcjKqXFBf7D97sF4WL7HER4LgA@mail.gmail.com>
	<8EBFBFBC-DAC2-4521-AE16-069F7FD8EFBC@postgresql.org>
	<CA+Tgmob1HFe-EbDmLs-xoQQfWAj8aB_cPToW-OOfhs4mFLfizg@mail.gmail.com>

Robert Haas <robertmhaas@gmail.com> writes:
> My primary concern about the patch is that
> ProcessGetMemoryContextInterrupt() can be called from any
> CHECK_FOR_INTERRUPTS() and calls lots of DSA functions, including
> dsa_create() and, via PublishMemoryContext(), dsa_allocate0(). I'm
> shocked to hear that you and Andres think that's safe to do at any
> current or future CHECK_FOR_INTERRUPTS() anywhere in the code; but
> Andres seems very confident that it's fine, so perhaps I should just
> stop worrying and be happy that we have the feature.

Just for the record, it sounds quite unsafe to me too.  I could
credit it being all right to examine the process' MemoryContext data
structures, but calling dsa_create() from CFI seems really insane.
Way too many moving parts there.

			regards, tom lane





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