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author | Linus Walleij <linus.walleij@linaro.org> | 2013-10-19 23:24:03 +0200 |
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committer | Linus Walleij <linus.walleij@linaro.org> | 2013-10-19 23:24:03 +0200 |
commit | b41fb43911b4cb864812adec88d028cc6219f23e (patch) | |
tree | f383de554dc3640ec3081ad41fa34f7cab68de82 /ipc/util.c | |
parent | 0963d59bc0bbed48b06733950f5eb167e9b9a8fa (diff) | |
parent | 31d141e3a666269a3b6fcccddb0351caf7454240 (diff) | |
download | linux-b41fb43911b4cb864812adec88d028cc6219f23e.tar.bz2 |
Merge tag 'v3.12-rc6' into devel
Linux 3.12-rc6
Conflicts:
drivers/gpio/gpio-lynxpoint.c
Diffstat (limited to 'ipc/util.c')
-rw-r--r-- | ipc/util.c | 27 |
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 @@ * 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) + * 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> |