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authorDavidlohr Bueso <davidlohr.bueso@hp.com>2013-09-11 14:26:26 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-09-11 15:59:43 -0700
commit05603c44a7627793219b0bd9a7b236099dc9cd9d (patch)
tree7efa266f81f6b68861bbea6cbda6baec48267408 /ipc
parent4718787d1f626f45ddb239912bc07266b9880044 (diff)
downloadlinux-05603c44a7627793219b0bd9a7b236099dc9cd9d.tar.gz
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>
Diffstat (limited to 'ipc')
-rw-r--r--ipc/util.c8
1 files changed, 8 insertions, 0 deletions
diff --git a/ipc/util.c b/ipc/util.c
index 9a1d779a20e..1ddadcf9a2a 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -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>