path: root/ipc/util.h
diff options
authorManfred Spraul <>2017-07-12 14:34:41 -0700
committerLinus Torvalds <>2017-07-12 16:26:01 -0700
commitdba4cdd39e698d8dcdad0656825423052ac90ccd (patch)
tree908f984f4652a42f603aac8f2db4edd059d11256 /ipc/util.h
parent1a23395672658969a4035dcc518ea6cab835c579 (diff)
ipc: merge ipc_rcu and kern_ipc_perm
ipc has two management structures that exist for every id: - struct kern_ipc_perm, it contains e.g. the permissions. - struct ipc_rcu, it contains the rcu head for rcu handling and the refcount. The patch merges both structures. As a bonus, we may save one cacheline, because both structures are cacheline aligned. In addition, it reduces the number of casts, instead most codepaths can use container_of. To simplify code, the ipc_rcu_alloc initializes the allocation to 0. [ really include the memset() into ipc_alloc_rcu()] Link: Link: Signed-off-by: Manfred Spraul <> Cc: Davidlohr Bueso <> Cc: Kees Cook <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'ipc/util.h')
1 files changed, 7 insertions, 11 deletions
diff --git a/ipc/util.h b/ipc/util.h
index 60ddccca464d..09d0f918c3e2 100644
--- a/ipc/util.h
+++ b/ipc/util.h
@@ -47,13 +47,6 @@ static inline void msg_exit_ns(struct ipc_namespace *ns) { }
static inline void shm_exit_ns(struct ipc_namespace *ns) { }
-struct ipc_rcu {
- struct rcu_head rcu;
- atomic_t refcount;
-} ____cacheline_aligned_in_smp;
-#define ipc_rcu_to_struct(p) ((void *)(p+1))
* Structure that holds the parameters needed by the ipc operations
* (see after)
@@ -125,11 +118,14 @@ void ipc_free(void *ptr);
* Objects are reference counted, they start with reference count 1.
* getref increases the refcount, the putref call that reduces the recount
* to 0 schedules the rcu destruction. Caller must guarantee locking.
+ *
+ * struct kern_ipc_perm must be the first member in the allocated structure.
-void *ipc_rcu_alloc(int size);
-int ipc_rcu_getref(void *ptr);
-void ipc_rcu_putref(void *ptr, void (*func)(struct rcu_head *head));
-void ipc_rcu_free(struct rcu_head *head);
+struct kern_ipc_perm *ipc_rcu_alloc(int size);
+int ipc_rcu_getref(struct kern_ipc_perm *ptr);
+void ipc_rcu_putref(struct kern_ipc_perm *ptr,
+ void (*func)(struct rcu_head *head));
+void ipc_rcu_free(struct rcu_head *h);
struct kern_ipc_perm *ipc_lock(struct ipc_ids *, int);
struct kern_ipc_perm *ipc_obtain_object_idr(struct ipc_ids *ids, int id);