[PATCH] X86: reboot-notify additions

[Cliff Wickman <cpw@sgi.com>]

From: Cliff Wickman <cpw@sgi.com>

X86 reboot-notify additions.

This patch adds scans of the "reboot_notifier_list" callback chain in
a three other places where the kernel is being stopped and/or restarted.

Adds calls to blocking_notifier_call_chain() in:
   crash_kexec(), emergency_restart(), sys_kexec_load()

In the crash_kexec() and emergency_restart() cases it is indicated to the
called-back function that the system is not in a sane state, so that
it can avoid taking a lock or some such potentially blocking action.

These callbacks are important to a partition system. The stopped kernel needs
to inform other partitions of their need to disconnect (stop sharing memory).

Diffed against 2.6.26-rc6

Signed-off-by: Cliff Wickman <cpw@sgi.com>
---
 include/linux/notifier.h |    4 ++++
 kernel/kexec.c           |    5 +++++
 kernel/sys.c             |    1 +
 3 files changed, 10 insertions(+)

Index: linux/include/linux/notifier.h
===================================================================
--- linux.orig/include/linux/notifier.h
+++ linux/include/linux/notifier.h
@@ -202,6 +202,10 @@ static inline int notifier_to_errno(int 
 #define SYS_RESTART	SYS_DOWN
 #define SYS_HALT	0x0002	/* Notify of system halt */
 #define SYS_POWER_OFF	0x0003	/* Notify of system power off */
+#define SYS_INSANE	0x0004	/* Notify of system error/panic/oops */
+/* For the SYS_INSANE case, no locks should be taken by the called-back
+ * function.  The kernel is ready for an immediate reboot.
+ */
 
 #define NETLINK_URELEASE	0x0001	/* Unicast netlink socket released */
 
Index: linux/kernel/kexec.c
===================================================================
--- linux.orig/kernel/kexec.c
+++ linux/kernel/kexec.c
@@ -1001,6 +1001,9 @@ asmlinkage long sys_kexec_load(unsigned 
 		if (result)
 			goto out;
 	}
+
+	blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, NULL);
+
 	/* Install the new kernel, and  Uninstall the old */
 	image = xchg(dest_image, image);
 
@@ -1068,6 +1071,8 @@ void crash_kexec(struct pt_regs *regs)
 	if (!locked) {
 		if (kexec_crash_image) {
 			struct pt_regs fixed_regs;
+			blocking_notifier_call_chain(&reboot_notifier_list,
+				SYS_INSANE, NULL);
 			crash_setup_regs(&fixed_regs, regs);
 			crash_save_vmcoreinfo();
 			machine_crash_shutdown(&fixed_regs);
Index: linux/kernel/sys.c
===================================================================
--- linux.orig/kernel/sys.c
+++ linux/kernel/sys.c
@@ -270,6 +270,7 @@ out_unlock:
  */
 void emergency_restart(void)
 {
+	blocking_notifier_call_chain(&reboot_notifier_list, SYS_INSANE, NULL);
 	machine_emergency_restart();
 }
 EXPORT_SYMBOL_GPL(emergency_restart);