diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c
index 4bb7c8e371a2..69a475aa0f44 100644
--- a/arch/powerpc/kernel/watchdog.c
+++ b/arch/powerpc/kernel/watchdog.c
@@ -85,10 +85,32 @@ static DEFINE_PER_CPU(u64, wd_timer_tb);
 
 /* SMP checker bits */
 static unsigned long __wd_smp_lock;
+static unsigned long __wd_reporting;
 static cpumask_t wd_smp_cpus_pending;
 static cpumask_t wd_smp_cpus_stuck;
 static u64 wd_smp_last_reset_tb;
 
+/*
+ * Try to take the exclusive watchdog action / NMI IPI / printing lock.
+ * wd_smp_lock must be held. If this fails, we should return and wait
+ * for the watchdog to kick in again (or another CPU to trigger it).
+ */
+static bool wd_try_report(void)
+{
+	if (__wd_reporting)
+		return false;
+	__wd_reporting = 1;
+	return true;
+}
+
+/* End printing after successful wd_try_report. wd_smp_lock not required. */
+static void wd_end_reporting(void)
+{
+	smp_mb(); /* End printing "critical section" */
+	WARN_ON_ONCE(__wd_reporting == 0);
+	WRITE_ONCE(__wd_reporting, 0);
+}
+
 static inline void wd_smp_lock(unsigned long *flags)
 {
 	/*
@@ -131,10 +153,10 @@ static void wd_lockup_ipi(struct pt_regs *regs)
 	/* Do not panic from here because that can recurse into NMI IPI layer */
 }
 
-static void set_cpumask_stuck(const struct cpumask *cpumask, u64 tb)
+static void set_cpu_stuck(int cpu, u64 tb)
 {
-	cpumask_or(&wd_smp_cpus_stuck, &wd_smp_cpus_stuck, cpumask);
-	cpumask_andnot(&wd_smp_cpus_pending, &wd_smp_cpus_pending, cpumask);
+	cpumask_set_cpu(cpu, &wd_smp_cpus_stuck);
+	cpumask_clear_cpu(cpu, &wd_smp_cpus_pending);
 	if (cpumask_empty(&wd_smp_cpus_pending)) {
 		wd_smp_last_reset_tb = tb;
 		cpumask_andnot(&wd_smp_cpus_pending,
@@ -142,10 +164,6 @@ static void set_cpumask_stuck(const struct cpumask *cpumask, u64 tb)
 				&wd_smp_cpus_stuck);
 	}
 }
-static void set_cpu_stuck(int cpu, u64 tb)
-{
-	set_cpumask_stuck(cpumask_of(cpu), tb);
-}
 
 static void watchdog_smp_panic(int cpu, u64 tb)
 {
@@ -160,6 +178,9 @@ static void watchdog_smp_panic(int cpu, u64 tb)
 		goto out;
 	if (cpumask_weight(&wd_smp_cpus_pending) == 0)
 		goto out;
+	if (!wd_try_report())
+		goto out;
+	wd_smp_unlock(&flags);
 
 	pr_emerg("CPU %d detected hard LOCKUP on other CPUs %*pbl\n",
 		 cpu, cpumask_pr_args(&wd_smp_cpus_pending));
@@ -172,24 +193,32 @@ static void watchdog_smp_panic(int cpu, u64 tb)
 		 * Try to trigger the stuck CPUs, unless we are going to
 		 * get a backtrace on all of them anyway.
 		 */
-		for_each_cpu(c, &wd_smp_cpus_pending) {
+		for_each_online_cpu(c) {
 			if (c == cpu)
 				continue;
+			if (!cpumask_test_cpu(cpu, &wd_smp_cpus_pending))
+				continue;
+			wd_smp_lock(&flags);
+			if (!cpumask_test_cpu(cpu, &wd_smp_cpus_pending)) {
+				wd_smp_unlock(&flags);
+				continue;
+			}
+			/* Take the stuck CPU out of the watch group */
+			set_cpu_stuck(cpu, tb);
+			wd_smp_unlock(&flags);
+
 			smp_send_nmi_ipi(c, wd_lockup_ipi, 1000000);
 		}
 	}
 
-	/* Take the stuck CPUs out of the watch group */
-	set_cpumask_stuck(&wd_smp_cpus_pending, tb);
-
-	wd_smp_unlock(&flags);
-
 	if (sysctl_hardlockup_all_cpu_backtrace)
 		trigger_allbutself_cpu_backtrace();
 
 	if (hardlockup_panic)
 		nmi_panic(NULL, "Hard LOCKUP");
 
+	wd_end_reporting();
+
 	return;
 
 out:
@@ -203,8 +232,6 @@ static void wd_smp_clear_cpu_pending(int cpu, u64 tb)
 			struct pt_regs *regs = get_irq_regs();
 			unsigned long flags;
 
-			wd_smp_lock(&flags);
-
 			pr_emerg("CPU %d became unstuck TB:%lld\n",
 				 cpu, tb);
 			print_irqtrace_events(current);
@@ -213,6 +240,7 @@ static void wd_smp_clear_cpu_pending(int cpu, u64 tb)
 			else
 				dump_stack();
 
+			wd_smp_lock(&flags);
 			cpumask_clear_cpu(cpu, &wd_smp_cpus_stuck);
 			wd_smp_unlock(&flags);
 		} else {
@@ -291,8 +319,17 @@ DEFINE_INTERRUPT_HANDLER_NMI(soft_nmi_interrupt)
 			wd_smp_unlock(&flags);
 			return 0;
 		}
+		if (!wd_try_report()) {
+			wd_smp_unlock(&flags);
+			/* Couldn't report, try again in 100ms */
+			mtspr(SPRN_DEC, 100 * tb_ticks_per_usec * 1000);
+			return 0;
+		}
+
 		set_cpu_stuck(cpu, tb);
 
+		wd_smp_unlock(&flags);
+
 		pr_emerg("CPU %d self-detected hard LOCKUP @ %pS\n",
 			 cpu, (void *)regs->nip);
 		pr_emerg("CPU %d TB:%lld, last heartbeat TB:%lld (%lldms ago)\n",
@@ -302,14 +339,19 @@ DEFINE_INTERRUPT_HANDLER_NMI(soft_nmi_interrupt)
 		print_irqtrace_events(current);
 		show_regs(regs);
 
-		wd_smp_unlock(&flags);
-
 		if (sysctl_hardlockup_all_cpu_backtrace)
 			trigger_allbutself_cpu_backtrace();
 
 		if (hardlockup_panic)
 			nmi_panic(regs, "Hard LOCKUP");
+
+		wd_end_reporting();
 	}
+	/*
+	 * We are okay to change DEC in soft_nmi_interrupt because the masked
+	 * handler has marked a DEC as pending, so the timer interrupt will be
+	 * replayed as soon as local irqs are enabled again.
+	 */
 	if (wd_panic_timeout_tb < 0x7fffffff)
 		mtspr(SPRN_DEC, wd_panic_timeout_tb);
 
