[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>

3 files changed, 4 insertions, 3 deletions

diff --git a/arch/mips/sgi-ip22/ip22-reset.c b/arch/mips/sgi-ip22/ip22-reset.c
index 8134220ed600..7a941ecff3bb 100644
--- a/arch/mips/sgi-ip22/ip22-reset.c
+++ b/arch/mips/sgi-ip22/ip22-reset.c
@@ -123,7 +123,8 @@ static inline void power_button(void)
         if (machine_state & MACHINE_PANICED)
                 return;
 
-        if ((machine_state & MACHINE_SHUTTING_DOWN) || kill_proc(1,SIGINT,1)) {
+        if ((machine_state & MACHINE_SHUTTING_DOWN) ||
+                        kill_cad_pid(SIGINT, 1)) {
                 /* No init process or button pressed twice.  */
                 sgi_machine_power_off();
         }
diff --git a/arch/mips/sgi-ip32/ip32-reset.c b/arch/mips/sgi-ip32/ip32-reset.c
index 79ddb4605659..fd0932b2d521 100644
--- a/arch/mips/sgi-ip32/ip32-reset.c
+++ b/arch/mips/sgi-ip32/ip32-reset.c
@@ -120,7 +120,7 @@ static inline void ip32_power_button(void)
         if (has_panicked)
                 return;
 
-        if (shuting_down || kill_proc(1, SIGINT, 1)) {
+        if (shuting_down || kill_cad_pid(SIGINT, 1)) {
                 /* No init process or button pressed twice.  */
                 ip32_machine_power_off();
         }
diff --git a/arch/powerpc/platforms/iseries/mf.c b/arch/powerpc/platforms/iseries/mf.c
index 1a2c2a50f922..1983b640bac1 100644
--- a/arch/powerpc/platforms/iseries/mf.c
+++ b/arch/powerpc/platforms/iseries/mf.c
@@ -357,7 +357,7 @@ static int dma_and_signal_ce_msg(char *ce_msg,
  */
 static int shutdown(void)
 {
-        int rc = kill_proc(1, SIGINT, 1);
+        int rc = kill_cad_pid(SIGINT, 1);
 
         if (rc) {
                 printk(KERN_ALERT "mf.c: SIGINT to init failed (%d), "