linux/ipc
Vasiliy Kulikov b34a6b1da3 ipc: introduce shm_rmid_forced sysctl
Add support for the shm_rmid_forced sysctl.  If set to 1, all shared
memory objects in current ipc namespace will be automatically forced to
use IPC_RMID.

The POSIX way of handling shmem allows one to create shm objects and
call shmdt(), leaving shm object associated with no process, thus
consuming memory not counted via rlimits.

With shm_rmid_forced=1 the shared memory object is counted at least for
one process, so OOM killer may effectively kill the fat process holding
the shared memory.

It obviously breaks POSIX - some programs relying on the feature would
stop working.  So set shm_rmid_forced=1 only if you're sure nobody uses
"orphaned" memory.  Use shm_rmid_forced=0 by default for compatability
reasons.

The feature was previously impemented in -ow as a configure option.

[akpm@linux-foundation.org: fix documentation, per Randy]
[akpm@linux-foundation.org: fix warning]
[akpm@linux-foundation.org: readability/conventionality tweaks]
[akpm@linux-foundation.org: fix shm_rmid_forced/shm_forced_rmid confusion, use standard comment layout]
Signed-off-by: Vasiliy Kulikov <segoon@openwall.com>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: "Serge E. Hallyn" <serge.hallyn@canonical.com>
Cc: Daniel Lezcano <daniel.lezcano@free.fr>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Solar Designer <solar@openwall.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-07-26 16:49:44 -07:00
..
Makefile Add generic sys_ipc wrapper 2010-03-12 15:52:32 -08:00
compat.c ipc: initialize structure memory to zero for compat functions 2010-10-27 18:03:13 -07:00
compat_mq.c ipc: initialize structure memory to zero for compat functions 2010-10-27 18:03:13 -07:00
ipc_sysctl.c ipc: introduce shm_rmid_forced sysctl 2011-07-26 16:49:44 -07:00
ipcns_notifier.c ipc: do not use a negative value to re-enable msgmni automatic recomputing 2008-07-25 10:53:42 -07:00
mq_sysctl.c sysctl ipc: Remove dead binary sysctl support code. 2009-11-12 02:04:54 -08:00
mqueue.c ipc/mqueue.c: fix mq_open() return value 2011-07-26 16:49:44 -07:00
msg.c Fix common misspellings 2011-03-31 11:26:23 -03:00
msgutil.c userns: add a user namespace owner of ipc ns 2011-03-23 19:47:07 -07:00
namespace.c ns proc: Add support for the ipc namespace 2011-05-10 14:35:47 -07:00
sem.c ipc/sem.c: fix race with concurrent semtimedop() timeouts and IPC_RMID 2011-07-25 20:57:07 -07:00
shm.c ipc: introduce shm_rmid_forced sysctl 2011-07-26 16:49:44 -07:00
syscall.c ppc64 sys_ipc breakage in 2.6.34-rc2 2010-03-22 09:57:19 -07:00
util.c ipc,rcu: Convert call_rcu(ipc_immediate_free) to kfree_rcu() 2011-07-20 14:10:16 -07:00
util.h userns: user namespaces: convert several capable() calls 2011-03-23 19:47:08 -07:00