watchdog: move softlockup_panic back to early_param

Setting softlockup_panic from do_sysctl_args() causes it to take effect
later in boot.  The lockup detector is enabled before SMP is brought
online, but do_sysctl_args runs afterwards.  If a user wants to set
softlockup_panic on boot and have it trigger should a softlockup occur
during onlining of the non-boot processors, they could do this prior to
commit f117955 ("kernel/watchdog.c: convert {soft/hard}lockup boot
parameters to sysctl aliases").  However, after this commit the value
of softlockup_panic is set too late to be of help for this type of
problem.  Restore the prior behavior.

Signed-off-by: Krister Johansen <kjlx@templeofstupid.com>
Cc: stable@vger.kernel.org
Fixes: f117955 ("kernel/watchdog.c: convert {soft/hard}lockup boot parameters to sysctl aliases")
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>

fs/proc/proc_sysctl.c

@@ -1576,7 +1576,6 @@ static const struct sysctl_alias sysctl_aliases[] = {
 	{"hung_task_panic",			"kernel.hung_task_panic" },
 	{"numa_zonelist_order",			"vm.numa_zonelist_order" },
 	{"softlockup_all_cpu_backtrace",	"kernel.softlockup_all_cpu_backtrace" },
-	{"softlockup_panic",			"kernel.softlockup_panic" },
 	{ }
 };
 

kernel/watchdog.c

@@ -283,6 +283,13 @@ static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
 static unsigned long soft_lockup_nmi_warn;
 
+static int __init softlockup_panic_setup(char *str)
+{
+	softlockup_panic = simple_strtoul(str, NULL, 0);
+	return 1;
+}
+__setup("softlockup_panic=", softlockup_panic_setup);
+
 static int __init nowatchdog_setup(char *str)
 {
 	watchdog_user_enabled = 0;