Horton

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

Thomas Munro <thomas.munro@enterprisedb.com>

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From: Thomas Munro <thomas.munro@enterprisedb.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
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: 2017-09-25T21:34:50Z
Lists: pgsql-hackers

Attachments

On Tue, Sep 26, 2017 at 10:12 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Thomas Munro <thomas.munro@enterprisedb.com> writes:
>> I think the problem here is that posix_fallocate() doesn't set errno.
>
> Huh.  So the fact that it worked for me is likely because glibc's
> emulation *does* allow errno to get set.
>
>> Will write a patch.
>
> Thanks, I'm out of time for today.

See attached, which also removes the ENOSYS stuff which I believe to
be now useless.  Does this make sense?  Survives make check-world and
my simple test procedure on a
3.10.0-327.36.1.el7.x86_64 system.

postgres=# select test_dsm(1000000000000);
ERROR:  could not resize shared memory segment
"/PostgreSQL.2043796572" to 1000000000000 bytes: No space left on
device
postgres=# select test_dsm(1000);
 test_dsm
----------

(1 row)

-- 
Thomas Munro
http://www.enterprisedb.com

Commits

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

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