[PATCH] replace cad_pid by a struct pid

There are a few places in the kernel where the init task is signaled.  The
ctrl+alt+del sequence is one them.  It kills a task, usually init, using a
cached pid (cad_pid).

This patch replaces the pid_t by a struct pid to avoid pid wrap around
problem.  The struct pid is initialized at boot time in init() and can be
modified through systctl with

	/proc/sys/kernel/cad_pid

[ I haven't found any distro using it ? ]

It also introduces a small helper routine kill_cad_pid() which is used
where it seemed ok to use cad_pid instead of pid 1.

[akpm@osdl.org: cleanups, build fix]
Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

4 files changed, 5 insertions, 7 deletions

diff --git a/drivers/char/nwbutton.c b/drivers/char/nwbutton.c
index 7c57ebfa8640..ea1aa7764f8e 100644
--- a/drivers/char/nwbutton.c
+++ b/drivers/char/nwbutton.c
@@ -127,9 +127,8 @@ static void button_consume_callbacks (int bpcount)
 static void button_sequence_finished (unsigned long parameters)
 {
 #ifdef CONFIG_NWBUTTON_REBOOT           /* Reboot using button is enabled */
-        if (button_press_count == reboot_count) {
-                kill_proc (1, SIGINT, 1);       /* Ask init to reboot us */
-        }
+        if (button_press_count == reboot_count)
+                kill_cad_pid(SIGINT, 1);        /* Ask init to reboot us */
 #endif /* CONFIG_NWBUTTON_REBOOT */
         button_consume_callbacks (button_press_count);
         bcount = sprintf (button_output_buffer, "%d\n", button_press_count);
diff --git a/drivers/char/snsc_event.c b/drivers/char/snsc_event.c
index d12d4f629cec..864854c58866 100644
--- a/drivers/char/snsc_event.c
+++ b/drivers/char/snsc_event.c
@@ -220,7 +220,7 @@ scdrv_dispatch_event(char *event, int len)
                                " Sending SIGPWR to init...\n");
 
                 /* give a SIGPWR signal to init proc */
-                kill_proc(1, SIGPWR, 0);
+                kill_cad_pid(SIGPWR, 0);
         } else {
                 /* print to system log */
                 printk("%s|$(0x%x)%s\n", severity, esp_code, desc);
diff --git a/drivers/parisc/power.c b/drivers/parisc/power.c
index fad5a33bf0fa..4a9f025a6b58 100644
--- a/drivers/parisc/power.c
+++ b/drivers/parisc/power.c
@@ -84,8 +84,7 @@
 
 static void deferred_poweroff(void *dummy)
 {
-        extern int cad_pid;     /* from kernel/sys.c */
-        if (kill_proc(cad_pid, SIGINT, 1)) {
+        if (kill_cad_pid(SIGINT, 1)) {
                 /* just in case killing init process failed */
                 machine_power_off();
         }
diff --git a/drivers/s390/s390mach.c b/drivers/s390/s390mach.c
index 479364d0332a..e088b5e28711 100644
--- a/drivers/s390/s390mach.c
+++ b/drivers/s390/s390mach.c
@@ -208,7 +208,7 @@ s390_handle_mcck(void)
                  */
                 __ctl_clear_bit(14, 24);        /* Disable WARNING MCH */
                 if (xchg(&mchchk_wng_posted, 1) == 0)
-                        kill_proc(1, SIGPWR, 1);
+                        kill_cad_pid(SIGPWR, 1);
         }
 #endif