Horton

Re: Server crash due to SIGBUS(Bus Error) when trying to access the memory created using dsm_create().

Tom Lane <tgl@sss.pgh.pa.us>

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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>
Date: 2017-09-25T18:56:34Z
Lists: pgsql-hackers 
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

Commits

  1. Fix failure-to-read-man-page in commit 899bd785c.

  2. Avoid SIGBUS on Linux when a DSM memory request overruns tmpfs.