[PATCH] add process_session() helper routine

Replace occurences of task->signal->session by a new process_session() helper
routine.

It will be useful for pid namespaces to abstract the session pid number.

Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
Cc: Kirill Korotaev <dev@openvz.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Herbert Poetzl <herbert@13thfloor.at>
Cc: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/drivers/char/mxser.c b/drivers/char/mxser.c
index 5ed2486..b1cc89c 100644
--- a/drivers/char/mxser.c
+++ b/drivers/char/mxser.c
@@ -994,7 +994,7 @@
 		mxser_change_speed(info, NULL);
 	}
 
-	info->session = current->signal->session;
+	info->session = process_session(current);
 	info->pgrp = process_group(current);
 
 	/*