From: Tom Lane <tgl@sss.pgh.pa.us>
To: Thomas Munro <thomas.munro@enterprisedb.com>
cc: Robert Haas <robertmhaas@gmail.com>, Andres Freund <andres@anarazel.de>,
        amul sul <sul_amul@yahoo.co.in>,
        PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: Server crash due to SIGBUS(Bus Error) when trying to access the
 memory created using dsm_create().
In-reply-to: <488.1506364109@sss.pgh.pa.us>
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Comments: In-reply-to Tom Lane <tgl@sss.pgh.pa.us>
	message dated "Mon, 25 Sep 2017 14:28:29 -0400"
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Date: Mon, 25 Sep 2017 14:56:34 -0400
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I wrote:
> Hmm, so I tested this patch on my RHEL6 box (kernel 2.6.32) and it
> immediately fell over with
> 2017-09-25 14:23:48.410 EDT [325] FATAL:  could not resize shared memory =
segment "/PostgreSQL.1682054886" to 6928 bytes: Operation not supported
> during startup.  I wonder whether we need to round off the request.

Nope, rounding off doesn't help.  What does help is using posix_fallocate
instead.  I surmise that glibc knows something we don't about how to call
fallocate(2) successfully on this kernel version.

Rather than dig into the guts of glibc to find that out, though, I think
we should just s/fallocate/posix_fallocate/g on this patch.  The argument
for using the former seemed pretty thin to begin with.

			regards, tom lane


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