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SubjectRe: [RFC] ipc: introduce shm_rmid_forced sysctl
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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