Commit 05603c44 authored by Davidlohr Bueso's avatar Davidlohr Bueso Committed by Linus Torvalds

ipc: document general ipc locking scheme

As suggested by Andrew, add a generic initial locking scheme used
throughout all sysv ipc mechanisms.  Documenting the ids rwsem, how rcu
can be enough to do the initial checks and when to actually acquire the
kern_ipc_perm.lock spinlock.

I found that adding it to util.c was generic enough.
Signed-off-by: default avatarDavidlohr Bueso <davidlohr.bueso@hp.com>
Tested-by: default avatarSedat Dilek <sedat.dilek@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4718787d
...@@ -15,6 +15,14 @@ ...@@ -15,6 +15,14 @@
* Jun 2006 - namespaces ssupport * Jun 2006 - namespaces ssupport
* OpenVZ, SWsoft Inc. * OpenVZ, SWsoft Inc.
* Pavel Emelianov <xemul@openvz.org> * Pavel Emelianov <xemul@openvz.org>
*
* General sysv ipc locking scheme:
* when doing ipc id lookups, take the ids->rwsem
* rcu_read_lock()
* obtain the ipc object (kern_ipc_perm)
* perform security, capabilities, auditing and permission checks, etc.
* acquire the ipc lock (kern_ipc_perm.lock) throught ipc_lock_object()
* perform data updates (ie: SET, RMID, LOCK/UNLOCK commands)
*/ */
#include <linux/mm.h> #include <linux/mm.h>
......
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