[PATCH] tty: update the tty layer to work with struct pid

Of kernel subsystems that work with pids the tty layer is probably the largest
consumer.  But it has the nice virtue that the assiation with a session only
lasts until the session leader exits.  Which means that no reference counting
is required.  So using struct pid winds up being a simple optimization to
avoid hash table lookups.

In the long term the use of pid_nr also ensures that when we have multiple pid
spaces mixed everything will work correctly.

Signed-off-by: Eric W. Biederman <eric@maxwell.lnxi.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 4 insertions, 4 deletions

diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 6383d2d83bb0..a2d95ff50e9b 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -66,7 +66,7 @@
         .cpu_timers     = INIT_CPU_TIMERS(sig.cpu_timers),              \
         .rlim           = INIT_RLIMITS,                                 \
         .pgrp           = 1,                                            \
-        .tty_old_pgrp   = 0,                                            \
+        .tty_old_pgrp   = NULL,                                         \
         { .__session      = 1},                                         \
 }
 
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 76c8e2dc48dd..39d40c518531 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -436,7 +436,7 @@ struct signal_struct {
 
         /* job control IDs */
         pid_t pgrp;
-        pid_t tty_old_pgrp;
+        struct pid *tty_old_pgrp;
 
         union {
                 pid_t session __deprecated;
diff --git a/include/linux/tty.h b/include/linux/tty.h
index d0e03c4a71b1..dee72b9a20fb 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -197,8 +197,8 @@ struct tty_struct {
         struct mutex termios_mutex;
         struct ktermios *termios, *termios_locked;
         char name[64];
-        int pgrp;
-        int session;
+        struct pid *pgrp;
+        struct pid *session;
         unsigned long flags;
         int count;
         struct winsize winsize;