Re: [RFC] ipc: introduce shm_rmid_forced sysctl

[Solar Designer]

On Wed, Jun 29, 2011 at 03:14:36PM -0700, Andrew Morton wrote:
> What a horrid patch.  But given the POSIX (mis?)feature I don't see a
> better way, and the feature seems desirable.  Sigh.
> 
> What sort of users would want to turn this on, and why?

Originally, I introduced it into Linux 2.0.x-ow to allow for resource
limits to be enforced on shared servers, such as with shared web
hosting.  A user is supposed to be limited by RLIMIT_AS * RLIMIT_NPROC.
(This is awfully inflexible, lacking a separate per-user memory limit,
but at least it's something.)  However, with shared memory segments a
user could bypass that limit, because those segments don't have to be
tied to a process.  So the patch changed that, requiring that any shm
segment be tied to a process, or be destroyed.

Alexander
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