kexec: use core_param for crash_kexec_post_notifiers boot option

crash_kexec_post_notifiers ia a boot option which controls whether the
1st kernel calls panic notifiers or not before booting the 2nd kernel.
However, there is no need to limit it to being modifiable only at boot
time.  So, use core_param instead of early_param.

Link: http://lkml.kernel.org/r/20160705113327.5864.43139.stgit@softrsSigned-off-by: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Borislav Petkov <bp@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/panic.c

@@ -108,6 +108,7 @@ void panic(const char *fmt, ...)
 	long i, i_next = 0;
 	int state = 0;
 	int old_cpu, this_cpu;
+	bool _crash_kexec_post_notifiers = crash_kexec_post_notifiers;
 
 	/*
 	 * Disable local interrupts. This will prevent panic_smp_self_stop
@@ -160,7 +161,7 @@ void panic(const char *fmt, ...)
 	 *
 	 * Bypass the panic_cpu check and call __crash_kexec directly.
 	 */
-	if (!crash_kexec_post_notifiers) {
+	if (!_crash_kexec_post_notifiers) {
 		printk_nmi_flush_on_panic();
 		__crash_kexec(NULL);
 	}
@@ -191,7 +192,7 @@ void panic(const char *fmt, ...)
 	 *
 	 * Bypass the panic_cpu check and call __crash_kexec directly.
 	 */
-	if (crash_kexec_post_notifiers)
+	if (_crash_kexec_post_notifiers)
 		__crash_kexec(NULL);
 
 	bust_spinlocks(0);
@@ -571,13 +572,7 @@ EXPORT_SYMBOL(__stack_chk_fail);
 core_param(panic, panic_timeout, int, 0644);
 core_param(pause_on_oops, pause_on_oops, int, 0644);
 core_param(panic_on_warn, panic_on_warn, int, 0644);
-
-static int __init setup_crash_kexec_post_notifiers(char *s)
-{
-	crash_kexec_post_notifiers = true;
-	return 0;
-}
-early_param("crash_kexec_post_notifiers", setup_crash_kexec_post_notifiers);
+core_param(crash_kexec_post_notifiers, crash_kexec_post_notifiers, bool, 0644);
 
 static int __init oops_setup(char *s)
 {