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-rw-r--r--ipc/util.c27
1 files changed, 21 insertions, 6 deletions
diff --git a/ipc/util.c b/ipc/util.c
index fdb8ae740775..7684f41bce76 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -17,12 +17,27 @@
17 * Pavel Emelianov <xemul@openvz.org> 17 * Pavel Emelianov <xemul@openvz.org>
18 * 18 *
19 * General sysv ipc locking scheme: 19 * General sysv ipc locking scheme:
20 * when doing ipc id lookups, take the ids->rwsem 20 * rcu_read_lock()
21 * rcu_read_lock() 21 * obtain the ipc object (kern_ipc_perm) by looking up the id in an idr
22 * obtain the ipc object (kern_ipc_perm) 22 * tree.
23 * perform security, capabilities, auditing and permission checks, etc. 23 * - perform initial checks (capabilities, auditing and permission,
24 * acquire the ipc lock (kern_ipc_perm.lock) throught ipc_lock_object() 24 * etc).
25 * perform data updates (ie: SET, RMID, LOCK/UNLOCK commands) 25 * - perform read-only operations, such as STAT, INFO commands.
26 * acquire the ipc lock (kern_ipc_perm.lock) through
27 * ipc_lock_object()
28 * - perform data updates, such as SET, RMID commands and
29 * mechanism-specific operations (semop/semtimedop,
30 * msgsnd/msgrcv, shmat/shmdt).
31 * drop the ipc lock, through ipc_unlock_object().
32 * rcu_read_unlock()
33 *
34 * The ids->rwsem must be taken when:
35 * - creating, removing and iterating the existing entries in ipc
36 * identifier sets.
37 * - iterating through files under /proc/sysvipc/
38 *
39 * Note that sems have a special fast path that avoids kern_ipc_perm.lock -
40 * see sem_lock().
26 */ 41 */
27 42
28#include <linux/mm.h> 43#include <linux/mm.h>