Re: 2.3.51 -- I am still seeing the"shmget: shm filesystem not mounted" error

From: Alan Cox (alan@lxorguk.ukuu.org.uk)
Date: Sun Mar 12 2000 - 13:12:31 EST


> The problem is that shm segments are like temporary files in a lot of
> way. You can't do open/unlink pass the name of a tmp file to another
> program either -- so why should you be able to do it with shm segments?

You can open/unlink and pass a temporary file by handle to another process

> To do open/unlink with multiple programs, you need some way to pass a
> file descriptor around.

We've got one.

> Besides, the creat/remove technique _still_ leaks from time to time. I
> have seen it -- more and more shm segments being added because a program
> crashed between the create and the remove.

its a very rare problem, lts make it happen every day.

> > Gimp wont be the only thing that breaks. So the old behaviour needs to work
> > at least for SYS5 IPC, what posix ipc does is another matter
>
> I propose we wait and see what else breaks.

Simple answer #1: doom, many apps using Gtk + shared memory pixmaps. Basically
it broke an established standardised API that we share with SYS5.4, *BSD and
almost everyone else.

> All the mess I can think of, including the "maps wrong SHM segment"
> problem are all fixed nicely by using fd passing over a unix socket.
> That, IMO, is the friendly way to establish a shm area with the X
> server.

Unfortunately you invented the idea fifteen years to late. XFree86 4.0
is also out so you missed your big window to implement this stuff. I'd suggest
you get looking into it for XFree 5.0 , in what five years time ?

Alan

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