1 files changed, 361 insertions, 157 deletions

diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c
index b67f8b03a32d..2429cb1c7baa 100644
--- a/arch/powerpc/kernel/watchdog.c
+++ b/arch/powerpc/kernel/watchdog.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Watchdog support on powerpc systems.
  *
@@ -5,6 +6,9 @@
  *
  * This uses code from arch/sparc/kernel/nmi.c and kernel/watchdog.c
  */
+
+#define pr_fmt(fmt) "watchdog: " fmt
+
 #include <linux/kernel.h>
 #include <linux/param.h>
 #include <linux/init.h>
@@ -20,20 +24,53 @@
 #include <linux/kdebug.h>
 #include <linux/sched/debug.h>
 #include <linux/delay.h>
+#include <linux/processor.h>
 #include <linux/smp.h>
 
+#include <asm/interrupt.h>
 #include <asm/paca.h>
+#include <asm/nmi.h>
 
 /*
- * The watchdog has a simple timer that runs on each CPU, once per timer
- * period. This is the heartbeat.
+ * The powerpc watchdog ensures that each CPU is able to service timers.
+ * The watchdog sets up a simple timer on each CPU to run once per timer
+ * period, and updates a per-cpu timestamp and a "pending" cpumask. This is
+ * the heartbeat.
+ *
+ * Then there are two systems to check that the heartbeat is still running.
+ * The local soft-NMI, and the SMP checker.
+ *
+ * The soft-NMI checker can detect lockups on the local CPU. When interrupts
+ * are disabled with local_irq_disable(), platforms that use soft-masking
+ * can leave hardware interrupts enabled and handle them with a masked
+ * interrupt handler. The masked handler can send the timer interrupt to the
+ * watchdog's soft_nmi_interrupt(), which appears to Linux as an NMI
+ * interrupt, and can be used to detect CPUs stuck with IRQs disabled.
+ *
+ * The soft-NMI checker will compare the heartbeat timestamp for this CPU
+ * with the current time, and take action if the difference exceeds the
+ * watchdog threshold.
  *
- * Then there are checks to see if the heartbeat has not triggered on a CPU
- * for the panic timeout period. Currently the watchdog only supports an
- * SMP check, so the heartbeat only turns on when we have 2 or more CPUs.
+ * The limitation of the soft-NMI watchdog is that it does not work when
+ * interrupts are hard disabled or otherwise not being serviced. This is
+ * solved by also having a SMP watchdog where all CPUs check all other
+ * CPUs heartbeat.
  *
- * This is not an NMI watchdog, but Linux uses that name for a generic
- * watchdog in some cases, so NMI gets used in some places.
+ * The SMP checker can detect lockups on other CPUs. A global "pending"
+ * cpumask is kept, containing all CPUs which enable the watchdog. Each
+ * CPU clears their pending bit in their heartbeat timer. When the bitmask
+ * becomes empty, the last CPU to clear its pending bit updates a global
+ * timestamp and refills the pending bitmask.
+ *
+ * In the heartbeat timer, if any CPU notices that the global timestamp has
+ * not been updated for a period exceeding the watchdog threshold, then it
+ * means the CPU(s) with their bit still set in the pending mask have had
+ * their heartbeat stop, and action is taken.
+ *
+ * Some platforms implement true NMI IPIs, which can be used by the SMP
+ * watchdog to detect an unresponsive CPU and pull it out of its stuck
+ * state with the NMI IPI, to get crash/debug data from it. This way the
+ * SMP watchdog can detect hardware interrupts off lockups.
  */
 
 static cpumask_t wd_cpus_enabled __read_mostly;
@@ -43,27 +80,46 @@ static u64 wd_smp_panic_timeout_tb __read_mostly; /* panic other CPUs */
 
 static u64 wd_timer_period_ms __read_mostly;  /* interval between heartbeat */
 
-static DEFINE_PER_CPU(struct timer_list, wd_timer);
+static DEFINE_PER_CPU(struct hrtimer, wd_hrtimer);
 static DEFINE_PER_CPU(u64, wd_timer_tb);
 
-/*
- * These are for the SMP checker. CPUs clear their pending bit in their
- * heartbeat. If the bitmask becomes empty, the time is noted and the
- * bitmask is refilled.
- *
- * All CPUs clear their bit in the pending mask every timer period.
- * Once all have cleared, the time is noted and the bits are reset.
- * If the time since all clear was greater than the panic timeout,
- * we can panic with the list of stuck CPUs.
- *
- * This will work best with NMI IPIs for crash code so the stuck CPUs
- * can be pulled out to get their backtraces.
- */
+/* SMP checker bits */
 static unsigned long __wd_smp_lock;
+static unsigned long __wd_reporting;
+static unsigned long __wd_nmi_output;
 static cpumask_t wd_smp_cpus_pending;
 static cpumask_t wd_smp_cpus_stuck;
 static u64 wd_smp_last_reset_tb;
 
+#ifdef CONFIG_PPC_PSERIES
+static u64 wd_timeout_pct;
+#endif
+
+/*
+ * 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).
+ *
+ * Importantly, if hardlockup_panic is set, wd_try_report failure should
+ * not delay the panic, because whichever other CPU is reporting will
+ * call panic.
+ */
+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)
 {
 	/*
@@ -71,20 +127,31 @@ static inline void wd_smp_lock(unsigned long *flags)
 	 * This may be called from low level interrupt handlers at some
 	 * point in future.
 	 */
-	local_irq_save(*flags);
-	while (unlikely(test_and_set_bit_lock(0, &__wd_smp_lock)))
-		cpu_relax();
+	raw_local_irq_save(*flags);
+	hard_irq_disable(); /* Make it soft-NMI safe */
+	while (unlikely(test_and_set_bit_lock(0, &__wd_smp_lock))) {
+		raw_local_irq_restore(*flags);
+		spin_until_cond(!test_bit(0, &__wd_smp_lock));
+		raw_local_irq_save(*flags);
+		hard_irq_disable();
+	}
 }
 
 static inline void wd_smp_unlock(unsigned long *flags)
 {
 	clear_bit_unlock(0, &__wd_smp_lock);
-	local_irq_restore(*flags);
+	raw_local_irq_restore(*flags);
 }
 
 static void wd_lockup_ipi(struct pt_regs *regs)
 {
-	pr_emerg("Watchdog CPU:%d Hard LOCKUP\n", raw_smp_processor_id());
+	int cpu = raw_smp_processor_id();
+	u64 tb = get_tb();
+
+	pr_emerg("CPU %d Hard LOCKUP\n", cpu);
+	pr_emerg("CPU %d TB:%lld, last heartbeat TB:%lld (%lldms ago)\n",
+		 cpu, tb, per_cpu(wd_timer_tb, cpu),
+		 tb_to_ns(tb - per_cpu(wd_timer_tb, cpu)) / 1000000);
 	print_modules();
 	print_irqtrace_events(current);
 	if (regs)
@@ -92,88 +159,182 @@ static void wd_lockup_ipi(struct pt_regs *regs)
 	else
 		dump_stack();
 
-	if (hardlockup_panic)
-		nmi_panic(regs, "Hard LOCKUP");
+	/*
+	 * __wd_nmi_output must be set after we printk from NMI context.
+	 *
+	 * printk from NMI context defers printing to the console to irq_work.
+	 * If that NMI was taken in some code that is hard-locked, then irqs
+	 * are disabled so irq_work will never fire. That can result in the
+	 * hard lockup messages being delayed (indefinitely, until something
+	 * else kicks the console drivers).
+	 *
+	 * Setting __wd_nmi_output will cause another CPU to notice and kick
+	 * the console drivers for us.
+	 *
+	 * xchg is not needed here (it could be a smp_mb and store), but xchg
+	 * gives the memory ordering and atomicity required.
+	 */
+	xchg(&__wd_nmi_output, 1);
+
+	/* Do not panic from here because that can recurse into NMI IPI layer */
 }
 
-static void set_cpu_stuck(int cpu, u64 tb)
+static bool set_cpu_stuck(int cpu)
 {
 	cpumask_set_cpu(cpu, &wd_smp_cpus_stuck);
 	cpumask_clear_cpu(cpu, &wd_smp_cpus_pending);
+	/*
+	 * See wd_smp_clear_cpu_pending()
+	 */
+	smp_mb();
 	if (cpumask_empty(&wd_smp_cpus_pending)) {
-		wd_smp_last_reset_tb = tb;
+		wd_smp_last_reset_tb = get_tb();
 		cpumask_andnot(&wd_smp_cpus_pending,
 				&wd_cpus_enabled,
 				&wd_smp_cpus_stuck);
+		return true;
 	}
+	return false;
 }
 
-static void watchdog_smp_panic(int cpu, u64 tb)
+static void watchdog_smp_panic(int cpu)
 {
+	static cpumask_t wd_smp_cpus_ipi; // protected by reporting
 	unsigned long flags;
+	u64 tb, last_reset;
 	int c;
 
 	wd_smp_lock(&flags);
 	/* Double check some things under lock */
-	if ((s64)(tb - wd_smp_last_reset_tb) < (s64)wd_smp_panic_timeout_tb)
+	tb = get_tb();
+	last_reset = wd_smp_last_reset_tb;
+	if ((s64)(tb - last_reset) < (s64)wd_smp_panic_timeout_tb)
 		goto out;
 	if (cpumask_test_cpu(cpu, &wd_smp_cpus_pending))
 		goto out;
-	if (cpumask_weight(&wd_smp_cpus_pending) == 0)
+	if (!wd_try_report())
 		goto out;
-
-	pr_emerg("Watchdog CPU:%d detected Hard LOCKUP other CPUS:%*pbl\n",
-			cpu, cpumask_pr_args(&wd_smp_cpus_pending));
-
-	/*
-	 * Try to trigger the stuck CPUs.
-	 */
-	for_each_cpu(c, &wd_smp_cpus_pending) {
-		if (c == cpu)
+	for_each_online_cpu(c) {
+		if (!cpumask_test_cpu(c, &wd_smp_cpus_pending))
 			continue;
-		smp_send_nmi_ipi(c, wd_lockup_ipi, 1000000);
-	}
-	smp_flush_nmi_ipi(1000000);
-
-	/* Take the stuck CPU out of the watch group */
-	for_each_cpu(c, &wd_smp_cpus_pending)
-		set_cpu_stuck(c, tb);
+		if (c == cpu)
+			continue; // should not happen
 
-out:
+		__cpumask_set_cpu(c, &wd_smp_cpus_ipi);
+		if (set_cpu_stuck(c))
+			break;
+	}
+	if (cpumask_empty(&wd_smp_cpus_ipi)) {
+		wd_end_reporting();
+		goto out;
+	}
 	wd_smp_unlock(&flags);
 
-	printk_safe_flush();
-	/*
-	 * printk_safe_flush() seems to require another print
-	 * before anything actually goes out to console.
-	 */
-	if (sysctl_hardlockup_all_cpu_backtrace)
-		trigger_allbutself_cpu_backtrace();
+	pr_emerg("CPU %d detected hard LOCKUP on other CPUs %*pbl\n",
+		 cpu, cpumask_pr_args(&wd_smp_cpus_ipi));
+	pr_emerg("CPU %d TB:%lld, last SMP heartbeat TB:%lld (%lldms ago)\n",
+		 cpu, tb, last_reset, tb_to_ns(tb - last_reset) / 1000000);
+
+	if (!sysctl_hardlockup_all_cpu_backtrace) {
+		/*
+		 * 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_ipi) {
+			smp_send_nmi_ipi(c, wd_lockup_ipi, 1000000);
+			__cpumask_clear_cpu(c, &wd_smp_cpus_ipi);
+		}
+	} else {
+		trigger_allbutcpu_cpu_backtrace(cpu);
+		cpumask_clear(&wd_smp_cpus_ipi);
+	}
 
 	if (hardlockup_panic)
 		nmi_panic(NULL, "Hard LOCKUP");
+
+	wd_end_reporting();
+
+	return;
+
+out:
+	wd_smp_unlock(&flags);
 }
 
-static void wd_smp_clear_cpu_pending(int cpu, u64 tb)
+static void wd_smp_clear_cpu_pending(int cpu)
 {
 	if (!cpumask_test_cpu(cpu, &wd_smp_cpus_pending)) {
 		if (unlikely(cpumask_test_cpu(cpu, &wd_smp_cpus_stuck))) {
+			struct pt_regs *regs = get_irq_regs();
 			unsigned long flags;
 
-			pr_emerg("Watchdog CPU:%d became unstuck\n", cpu);
+			pr_emerg("CPU %d became unstuck TB:%lld\n",
+				 cpu, get_tb());
+			print_irqtrace_events(current);
+			if (regs)
+				show_regs(regs);
+			else
+				dump_stack();
+
 			wd_smp_lock(&flags);
 			cpumask_clear_cpu(cpu, &wd_smp_cpus_stuck);
 			wd_smp_unlock(&flags);
+		} else {
+			/*
+			 * The last CPU to clear pending should have reset the
+			 * watchdog so we generally should not find it empty
+			 * here if our CPU was clear. However it could happen
+			 * due to a rare race with another CPU taking the
+			 * last CPU out of the mask concurrently.
+			 *
+			 * We can't add a warning for it. But just in case
+			 * there is a problem with the watchdog that is causing
+			 * the mask to not be reset, try to kick it along here.
+			 */
+			if (unlikely(cpumask_empty(&wd_smp_cpus_pending)))
+				goto none_pending;
 		}
 		return;
 	}
+
+	/*
+	 * All other updates to wd_smp_cpus_pending are performed under
+	 * wd_smp_lock. All of them are atomic except the case where the
+	 * mask becomes empty and is reset. This will not happen here because
+	 * cpu was tested to be in the bitmap (above), and a CPU only clears
+	 * its own bit. _Except_ in the case where another CPU has detected a
+	 * hard lockup on our CPU and takes us out of the pending mask. So in
+	 * normal operation there will be no race here, no problem.
+	 *
+	 * In the lockup case, this atomic clear-bit vs a store that refills
+	 * other bits in the accessed word wll not be a problem. The bit clear
+	 * is atomic so it will not cause the store to get lost, and the store
+	 * will never set this bit so it will not overwrite the bit clear. The
+	 * only way for a stuck CPU to return to the pending bitmap is to
+	 * become unstuck itself.
+	 */
 	cpumask_clear_cpu(cpu, &wd_smp_cpus_pending);
+
+	/*
+	 * Order the store to clear pending with the load(s) to check all
+	 * words in the pending mask to check they are all empty. This orders
+	 * with the same barrier on another CPU. This prevents two CPUs
+	 * clearing the last 2 pending bits, but neither seeing the other's
+	 * store when checking if the mask is empty, and missing an empty
+	 * mask, which ends with a false positive.
+	 */
+	smp_mb();
 	if (cpumask_empty(&wd_smp_cpus_pending)) {
 		unsigned long flags;
 
+none_pending:
+		/*
+		 * Double check under lock because more than one CPU could see
+		 * a clear mask with the lockless check after clearing their
+		 * pending bits.
+		 */
 		wd_smp_lock(&flags);
 		if (cpumask_empty(&wd_smp_cpus_pending)) {
-			wd_smp_last_reset_tb = tb;
+			wd_smp_last_reset_tb = get_tb();
 			cpumask_andnot(&wd_smp_cpus_pending,
 					&wd_cpus_enabled,
 					&wd_smp_cpus_stuck);
@@ -188,142 +349,194 @@ static void watchdog_timer_interrupt(int cpu)
 
 	per_cpu(wd_timer_tb, cpu) = tb;
 
-	wd_smp_clear_cpu_pending(cpu, tb);
+	wd_smp_clear_cpu_pending(cpu);
 
 	if ((s64)(tb - wd_smp_last_reset_tb) >= (s64)wd_smp_panic_timeout_tb)
-		watchdog_smp_panic(cpu, tb);
+		watchdog_smp_panic(cpu);
+
+	if (__wd_nmi_output && xchg(&__wd_nmi_output, 0)) {
+		/*
+		 * Something has called printk from NMI context. It might be
+		 * stuck, so this triggers a flush that will get that
+		 * printk output to the console.
+		 *
+		 * See wd_lockup_ipi.
+		 */
+		printk_trigger_flush();
+	}
 }
 
-void soft_nmi_interrupt(struct pt_regs *regs)
+DEFINE_INTERRUPT_HANDLER_NMI(soft_nmi_interrupt)
 {
 	unsigned long flags;
 	int cpu = raw_smp_processor_id();
 	u64 tb;
 
+	/* should only arrive from kernel, with irqs disabled */
+	WARN_ON_ONCE(!arch_irq_disabled_regs(regs));
+
 	if (!cpumask_test_cpu(cpu, &wd_cpus_enabled))
-		return;
+		return 0;
+
+	__this_cpu_inc(irq_stat.soft_nmi_irqs);
 
-	nmi_enter();
 	tb = get_tb();
 	if (tb - per_cpu(wd_timer_tb, cpu) >= wd_panic_timeout_tb) {
-		per_cpu(wd_timer_tb, cpu) = tb;
-
+		/*
+		 * Taking wd_smp_lock here means it is a soft-NMI lock, which
+		 * means we can't take any regular or irqsafe spin locks while
+		 * holding this lock. This is why timers can't printk while
+		 * holding the lock.
+		 */
 		wd_smp_lock(&flags);
 		if (cpumask_test_cpu(cpu, &wd_smp_cpus_stuck)) {
 			wd_smp_unlock(&flags);
-			goto out;
+			return 0;
 		}
-		set_cpu_stuck(cpu, tb);
+		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);
 
-		pr_emerg("Watchdog CPU:%d Hard LOCKUP\n", cpu);
+		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",
+			 cpu, tb, per_cpu(wd_timer_tb, cpu),
+			 tb_to_ns(tb - per_cpu(wd_timer_tb, cpu)) / 1000000);
 		print_modules();
 		print_irqtrace_events(current);
-		if (regs)
-			show_regs(regs);
-		else
-			dump_stack();
+		show_regs(regs);
 
-		wd_smp_unlock(&flags);
+		xchg(&__wd_nmi_output, 1); // see wd_lockup_ipi
 
 		if (sysctl_hardlockup_all_cpu_backtrace)
-			trigger_allbutself_cpu_backtrace();
+			trigger_allbutcpu_cpu_backtrace(cpu);
 
 		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);
 
-out:
-	nmi_exit();
-}
-
-static void wd_timer_reset(unsigned int cpu, struct timer_list *t)
-{
-	t->expires = jiffies + msecs_to_jiffies(wd_timer_period_ms);
-	if (wd_timer_period_ms > 1000)
-		t->expires = __round_jiffies_up(t->expires, cpu);
-	add_timer_on(t, cpu);
+	return 0;
 }
 
-static void wd_timer_fn(unsigned long data)
+static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 {
-	struct timer_list *t = this_cpu_ptr(&wd_timer);
 	int cpu = smp_processor_id();
 
+	if (!(watchdog_enabled & WATCHDOG_HARDLOCKUP_ENABLED))
+		return HRTIMER_NORESTART;
+
+	if (!cpumask_test_cpu(cpu, &watchdog_cpumask))
+		return HRTIMER_NORESTART;
+
 	watchdog_timer_interrupt(cpu);
 
-	wd_timer_reset(cpu, t);
+	hrtimer_forward_now(hrtimer, ms_to_ktime(wd_timer_period_ms));
+
+	return HRTIMER_RESTART;
 }
 
 void arch_touch_nmi_watchdog(void)
 {
+	unsigned long ticks = tb_ticks_per_usec * wd_timer_period_ms * 1000;
 	int cpu = smp_processor_id();
+	u64 tb;
 
-	watchdog_timer_interrupt(cpu);
-}
-EXPORT_SYMBOL(arch_touch_nmi_watchdog);
-
-static void start_watchdog_timer_on(unsigned int cpu)
-{
-	struct timer_list *t = per_cpu_ptr(&wd_timer, cpu);
-
-	per_cpu(wd_timer_tb, cpu) = get_tb();
+	if (!cpumask_test_cpu(cpu, &watchdog_cpumask))
+		return;
 
-	setup_pinned_timer(t, wd_timer_fn, 0);
-	wd_timer_reset(cpu, t);
+	tb = get_tb();
+	if (tb - per_cpu(wd_timer_tb, cpu) >= ticks) {
+		per_cpu(wd_timer_tb, cpu) = tb;
+		wd_smp_clear_cpu_pending(cpu);
+	}
 }
+EXPORT_SYMBOL(arch_touch_nmi_watchdog);
 
-static void stop_watchdog_timer_on(unsigned int cpu)
+static void start_watchdog(void *arg)
 {
-	struct timer_list *t = per_cpu_ptr(&wd_timer, cpu);
-
-	del_timer_sync(t);
-}
+	struct hrtimer *hrtimer = this_cpu_ptr(&wd_hrtimer);
+	int cpu = smp_processor_id();
+	unsigned long flags;
 
-static int start_wd_on_cpu(unsigned int cpu)
-{
 	if (cpumask_test_cpu(cpu, &wd_cpus_enabled)) {
 		WARN_ON(1);
-		return 0;
+		return;
 	}
 
-	if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
-		return 0;
-
-	if (watchdog_suspended)
-		return 0;
+	if (!(watchdog_enabled & WATCHDOG_HARDLOCKUP_ENABLED))
+		return;
 
 	if (!cpumask_test_cpu(cpu, &watchdog_cpumask))
-		return 0;
+		return;
 
+	wd_smp_lock(&flags);
 	cpumask_set_cpu(cpu, &wd_cpus_enabled);
 	if (cpumask_weight(&wd_cpus_enabled) == 1) {
 		cpumask_set_cpu(cpu, &wd_smp_cpus_pending);
 		wd_smp_last_reset_tb = get_tb();
 	}
-	smp_wmb();
-	start_watchdog_timer_on(cpu);
+	wd_smp_unlock(&flags);
 
-	return 0;
+	*this_cpu_ptr(&wd_timer_tb) = get_tb();
+
+	hrtimer_setup(hrtimer, watchdog_timer_fn, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+	hrtimer_start(hrtimer, ms_to_ktime(wd_timer_period_ms),
+		      HRTIMER_MODE_REL_PINNED);
+}
+
+static int start_watchdog_on_cpu(unsigned int cpu)
+{
+	return smp_call_function_single(cpu, start_watchdog, NULL, true);
 }
 
-static int stop_wd_on_cpu(unsigned int cpu)
+static void stop_watchdog(void *arg)
 {
+	struct hrtimer *hrtimer = this_cpu_ptr(&wd_hrtimer);
+	int cpu = smp_processor_id();
+	unsigned long flags;
+
 	if (!cpumask_test_cpu(cpu, &wd_cpus_enabled))
-		return 0; /* Can happen in CPU unplug case */
+		return; /* Can happen in CPU unplug case */
 
-	stop_watchdog_timer_on(cpu);
+	hrtimer_cancel(hrtimer);
 
+	wd_smp_lock(&flags);
 	cpumask_clear_cpu(cpu, &wd_cpus_enabled);
-	wd_smp_clear_cpu_pending(cpu, get_tb());
+	wd_smp_unlock(&flags);
 
-	return 0;
+	wd_smp_clear_cpu_pending(cpu);
+}
+
+static int stop_watchdog_on_cpu(unsigned int cpu)
+{
+	return smp_call_function_single(cpu, stop_watchdog, NULL, true);
 }
 
 static void watchdog_calc_timeouts(void)
 {
-	wd_panic_timeout_tb = watchdog_thresh * ppc_tb_freq;
+	u64 threshold = watchdog_thresh;
+
+#ifdef CONFIG_PPC_PSERIES
+	threshold += (READ_ONCE(wd_timeout_pct) * threshold) / 100;
+#endif
+
+	wd_panic_timeout_tb = threshold * ppc_tb_freq;
 
 	/* Have the SMP detector trigger a bit later */
 	wd_smp_panic_timeout_tb = wd_panic_timeout_tb * 3 / 2;
@@ -332,55 +545,46 @@ static void watchdog_calc_timeouts(void)
 	wd_timer_period_ms = watchdog_thresh * 1000 * 2 / 5;
 }
 
-void watchdog_nmi_reconfigure(void)
+void watchdog_hardlockup_stop(void)
 {
 	int cpu;
 
-	watchdog_calc_timeouts();
-
 	for_each_cpu(cpu, &wd_cpus_enabled)
-		stop_wd_on_cpu(cpu);
-
-	for_each_cpu_and(cpu, cpu_online_mask, &watchdog_cpumask)
-		start_wd_on_cpu(cpu);
+		stop_watchdog_on_cpu(cpu);
 }
 
-/*
- * This runs after lockup_detector_init() which sets up watchdog_cpumask.
- */
-static int __init powerpc_watchdog_init(void)
+void watchdog_hardlockup_start(void)
 {
-	int err;
+	int cpu;
 
 	watchdog_calc_timeouts();
-
-	err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "powerpc/watchdog:online",
-				start_wd_on_cpu, stop_wd_on_cpu);
-	if (err < 0)
-		pr_warn("Watchdog could not be initialized");
-
-	return 0;
-}
-arch_initcall(powerpc_watchdog_init);
-
-static void handle_backtrace_ipi(struct pt_regs *regs)
-{
-	nmi_cpu_backtrace(regs);
+	for_each_cpu_and(cpu, cpu_online_mask, &watchdog_cpumask)
+		start_watchdog_on_cpu(cpu);
 }
 
-static void raise_backtrace_ipi(cpumask_t *mask)
+/*
+ * Invoked from core watchdog init.
+ */
+int __init watchdog_hardlockup_probe(void)
 {
-	unsigned int cpu;
+	int err;
 
-	for_each_cpu(cpu, mask) {
-		if (cpu == smp_processor_id())
-			handle_backtrace_ipi(NULL);
-		else
-			smp_send_nmi_ipi(cpu, handle_backtrace_ipi, 1000000);
+	err = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
+					"powerpc/watchdog:online",
+					start_watchdog_on_cpu,
+					stop_watchdog_on_cpu);
+	if (err < 0) {
+		pr_warn("could not be initialized");
+		return err;
 	}
+	return 0;
 }
 
-void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
+#ifdef CONFIG_PPC_PSERIES
+void watchdog_hardlockup_set_timeout_pct(u64 pct)
 {
-	nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_backtrace_ipi);
+	pr_info("Set the NMI watchdog timeout factor to %llu%%\n", pct);
+	WRITE_ONCE(wd_timeout_pct, pct);
+	lockup_detector_reconfigure();
 }
+#endif