| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
| Cc: | Petr Jelinek <petr(dot)jelinek(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Magnus Hagander <magnus(at)hagander(dot)net>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, "Tsunakawa, Takayuki" <tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com>, Noah Misch <noah(at)leadboat(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: retry shm attach for windows (WAS: Re: OK, so culicidae is *still* broken) |
| Date: | 2017-06-05 13:56:33 |
| Message-ID: | 32199.1496670993@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> writes:
> Sure. I think it is slightly tricky because specs don't say clearly
> how ASLR can impact the behavior of any API and in my last attempt I
> could not reproduce the issue.
> I can try to do basic verification with the patch you have proposed,
> but I fear, to do the actual tests as suggested by you is difficult as
> it is not reproducible on my machine, but I can still try.
Yeah, being able to reproduce the problem reliably enough to say whether
it's fixed or not is definitely the sticking point here. I have some
ideas about that:
1. Be sure to use Win32 not Win64 --- the odds of a failure in the larger
address space are so small you'd never prove anything. (And of course
it has to be a version that has ASLR enabled.)
2. Revert 7f3e17b48 so that you have an ASLR-enabled build.
3. Crank shared_buffers to the maximum the machine will allow, reducing
the amount of free address space and improving the odds of a collision.
4. Spawn lots of sessions --- pgbench with -C option might be a useful
testing tool.
With luck, that will get failures often enough that you can be pretty
sure whether a patch improves the situation or not.
regards, tom lane
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