x86/traps: die() instead of panicking on a double fault

A double fault has a decent chance of being recoverable by killing
the offending thread.  Use die() so that we at least try to recover.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/traps.c

@@ -427,7 +427,7 @@ dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code, unsign
 #endif
 
 	pr_emerg("PANIC: double fault, error_code: 0x%lx\n", error_code);
-	show_regs(regs);
+	die("double fault", regs, error_code);
 	panic("Machine halted.");
 }
 #endif