clarify kill and delete operation

Signed-off-by: lifubang <[email protected]>

Author: lifubang

Diff for: runtime.md

@@ -129,18 +129,19 @@ This operation MUST run the user-specified program as specified by [`process`](c
 This operation MUST generate an error if `process` was not set.
 
 ### <a name="runtimeKill" />Kill
-`kill <container-id> <signal>`
+`kill <container-id> [-a,--all] <signal>`
 
 This operation MUST [generate an error](#errors) if it is not provided the container ID.
-Attempting to send a signal to a container that is neither [`created` nor `running`](#state) MUST have no effect on the container and MUST [generate an error](#errors).
-This operation MUST send the specified signal to the container process.
+This operation MUST send the specified signal to the container process(without `-a`) or to all processes in the container(with `-a`).
+Without `-a`, attempting to send a signal to a container that is neither [`created` nor `running`](#state) MUST have no effect on the container and MUST [generate an error](#errors).
 
 ### <a name="runtimeDelete" />Delete
-`delete <container-id>`
+`delete [-f,--force] <container-id>`
 
 This operation MUST [generate an error](#errors) if it is not provided the container ID.
-Attempting to `delete` a container that is not [`stopped`](#state) MUST have no effect on the container and MUST [generate an error](#errors).
-Deleting a container MUST delete the resources that were created during the `create` step.
+Without `-f`, attempting to `delete` a container that is not [`stopped`](#state) MUST have no effect on the container and MUST [generate an error](#errors).
+With `-f`, runtime should try its best to delete the container no matter what the state is.
+Deleting a container MUST delete the resources that were created during the `create` step, specially, if the container uses `shared pid namespace`, all processes inside the container's cgroup should also be killed first.
 Note that resources associated with the container, but not created by this container, MUST NOT be deleted.
 Once a container is deleted its ID MAY be used by a subsequent container.