Commit 05603c44 authored Sep 11, 2013 by Davidlohr Bueso Committed by Linus Torvalds Sep 11, 2013

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: Davidlohr Bueso <davidlohr.bueso@hp.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 4718787d

ipc/util.c

+8 −0

Original line number	Diff line number	Diff line
		@@ -15,6 +15,14 @@
		* Jun 2006 - namespaces ssupport
		* OpenVZ, SWsoft Inc.
		* 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>