Re: DSM robustness failure (was Re: Peripatus/failures)

On Thu, Oct 18, 2018 at 02:17:14PM +1300, Thomas Munro wrote:
> On Thu, Oct 18, 2018 at 1:10 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> > ... However, I'm still slightly interested in how it
> > was that that broke DSM so thoroughly ...
>
> Me too. Frustratingly, that vm object might still exist on Larry's
> machine if it hasn't been rebooted (since we failed to shm_unlink()
> it), so if we knew its name we could write a program to shm_open(),
> mmap(), dump out to a file for analysis and then we could work out
> which of the sanity tests it failed and maybe get some clues.
> Unfortunately it's not in any of our logs AFAIK, and I can't see any
> way to get a list of existing shm_open() objects from the kernel.
> From sys/kern/uipc_shm.c:
>
> * TODO:
> *
> * (1) Need to export data to a userland tool via a sysctl. Should ipcs(1)
> * and ipcrm(1) be expanded or should new tools to manage both POSIX
> * kernel semaphores and POSIX shared memory be written?
>
> Gah. So basically that's hiding in shm_dictionary in the kernel and I
> don't know a way to look at it from userspace (other than trying to
> open all 2^32 random paths we're capable of generating).

It has *NOT* been rebooted. I can give y'all id's if you want to go
poking around.

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

--
Larry Rosenman http://www.lerctr.org/~ler
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