watchdog: if panicking and we dumped everything, don't re-enable dumping

If, as part of handling a hardlockup or softlockup, we've already dumped
all CPUs and we're just about to panic, don't reenable dumping and give
some other CPU a chance to hop in there and add some confusing logs right
as the panic is happening.

Link: https://lkml.kernel.org/r/20231220131534.4.Id3a9c7ec2d7d83e4080da6f8662ba2226b40543f@changeid
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Li Zhe <lizhe.67@bytedance.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Pingfan Liu <kernelfans@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: dianders

kernel/watchdog.c

@@ -192,7 +192,8 @@ void watchdog_hardlockup_check(unsigned int cpu, struct pt_regs *regs)
 
 		if (sysctl_hardlockup_all_cpu_backtrace) {
 			trigger_allbutcpu_cpu_backtrace(cpu);
-			clear_bit_unlock(0, &hard_lockup_nmi_warn);
+			if (!hardlockup_panic)
+				clear_bit_unlock(0, &hard_lockup_nmi_warn);
 		}
 
 		if (hardlockup_panic)
@@ -548,7 +549,8 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 
 		if (softlockup_all_cpu_backtrace) {
 			trigger_allbutcpu_cpu_backtrace(smp_processor_id());
-			clear_bit_unlock(0, &soft_lockup_nmi_warn);
+			if (!softlockup_panic)
+				clear_bit_unlock(0, &soft_lockup_nmi_warn);
 		}
 
 		add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);