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@sss.pgh.pa.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
Phone: +1 214-642-9640                 E-Mail: ler@lerctr.org
US Mail: 5708 Sabbia Drive, Round Rock, TX 78665-2106