From: Carlos Bilbao <carlos.bilbao@kernel.org>

Add function x86_panic_handler() as the default behavior for x86 for
post-panic stage via panic_set_handling(). Instead of busy-wait loop, it
will halt if there's no console to save CPU cycles.

Signed-off-by: Carlos Bilbao (DigitalOcean) <carlos.bilbao@kernel.org>
Reviewed-by: Jan Glauber (DigitalOcean) <jan.glauber@gmail.com>
---
 arch/x86/kernel/setup.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 9d2a13b37833..abca4a9b5e0a 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -16,6 +16,7 @@
 #include <linux/initrd.h>
 #include <linux/iscsi_ibft.h>
 #include <linux/memblock.h>
+#include <linux/panic.h>
 #include <linux/panic_notifier.h>
 #include <linux/pci.h>
 #include <linux/root_dev.h>
@@ -837,6 +838,20 @@ static void __init x86_report_nx(void)
 	}
 }
 
+/*
+ * Halt the CPU to save resources after panic is handled. If
+ * console_trylock() succeeds, no other CPU is currently writing to the
+ * console
+ *
+ */
+static void x86_panic_handler(void)
+{
+	if (console_trylock()) {
+		console_unlock();
+		safe_halt();
+	}
+}
+
 /*
  * Determine if we were loaded by an EFI loader.  If so, then we have also been
  * passed the efi memmap, systab, etc., so we should use these data structures
@@ -1252,6 +1267,8 @@ void __init setup_arch(char **cmdline_p)
 #endif
 
 	unwind_init();
+
+	panic_set_handling(x86_panic_handler, 0);
 }
 
 #ifdef CONFIG_X86_32
-- 
2.47.1