3.11.10.1 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Davidlohr Bueso <davidlohr@xxxxxx> commit 18ccee263c7e250a57f01c9434658f11f4118a64 upstream. The initial documentation was a bit incomplete, update accordingly. [akpm@xxxxxxxxxxxxxxxxxxxx: make it more readable in 80 columns] Signed-off-by: Davidlohr Bueso <davidlohr@xxxxxx> Acked-by: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx> --- ipc/util.c | 27 +++++++++++++++++++++------ 1 file changed, 21 insertions(+), 6 deletions(-) diff --git a/ipc/util.c b/ipc/util.c index fdb8ae7..7684f41 100644 --- a/ipc/util.c +++ b/ipc/util.c @@ -17,12 +17,27 @@ * Pavel Emelianov <xemul@xxxxxxxxxx> * * 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) + * rcu_read_lock() + * obtain the ipc object (kern_ipc_perm) by looking up the id in an idr + * tree. + * - perform initial checks (capabilities, auditing and permission, + * etc). + * - perform read-only operations, such as STAT, INFO commands. + * acquire the ipc lock (kern_ipc_perm.lock) through + * ipc_lock_object() + * - perform data updates, such as SET, RMID commands and + * mechanism-specific operations (semop/semtimedop, + * msgsnd/msgrcv, shmat/shmdt). + * drop the ipc lock, through ipc_unlock_object(). + * rcu_read_unlock() + * + * The ids->rwsem must be taken when: + * - creating, removing and iterating the existing entries in ipc + * identifier sets. + * - iterating through files under /proc/sysvipc/ + * + * Note that sems have a special fast path that avoids kern_ipc_perm.lock - + * see sem_lock(). */ #include <linux/mm.h> -- 1.8.3.2 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html