MIPS: die() does not call die notifier chain

The MIPS implementation of die() forgets to call notify_die() and thus notifiers
registered via register_die_notifier() are not called.  This results in kgdb not
being activated on exceptions.

The only subtlety is that notify_die declares its regs argument w/o const, so
the const had to be removed from mips die() as well.

[Ralf: Fixed build error for SGI IP22 and IP28 platforms.]

Signed-off-by: Yury Polyanskiy <ypolyans@princeton.edu>
Cc: linux-mips@linux-mips.org
Patchworks: http://patchwork.linux-mips.org/patch/1142/
Acked-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

---
diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index 1a4dd65..36460c7 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -352,9 +352,10 @@
 
 static DEFINE_SPINLOCK(die_lock);
 
-void __noreturn die(const char * str, const struct pt_regs * regs)
+void __noreturn die(const char * str, struct pt_regs * regs)
 {
 	static int die_counter;
+	int sig = SIGSEGV;
 #ifdef CONFIG_MIPS_MT_SMTC
 	unsigned long dvpret = dvpe();
 #endif /* CONFIG_MIPS_MT_SMTC */
@@ -365,6 +366,10 @@
 #ifdef CONFIG_MIPS_MT_SMTC
 	mips_mt_regdump(dvpret);
 #endif /* CONFIG_MIPS_MT_SMTC */
+
+	if (notify_die(DIE_OOPS, str, regs, 0, current->thread.trap_no, SIGSEGV) == NOTIFY_STOP)
+		sig = 0;
+
 	printk("%s[#%d]:\n", str, ++die_counter);
 	show_registers(regs);
 	add_taint(TAINT_DIE);
@@ -379,7 +384,7 @@
 		panic("Fatal exception");
 	}
 
-	do_exit(SIGSEGV);
+	do_exit(sig);
 }
 
 extern struct exception_table_entry __start___dbe_table[];