watchdog/core, powerpc: Replace watchdog_nmi_reconfigure()

The recent cleanup of the watchdog code split watchdog_nmi_reconfigure()
into two stages. One to stop the NMI and one to restart it after
reconfiguration. That was done by adding a boolean 'run' argument to the
code, which is functionally correct but not necessarily a piece of art.

Replace it by two explicit functions: watchdog_nmi_stop() and
watchdog_nmi_start().

Fixes: 6592ad2f ("watchdog/core, powerpc: Make watchdog_nmi_reconfigure() two stage")
Requested-by: Linus 'Nursing his pet-peeve' Torvalds <torvalds@linuxfoundation.org>
Signed-off-by: Thomas 'Mopping up garbage' Gleixner <tglx@linutronix.de>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: linuxppc-dev@lists.ozlabs.org
Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1710021957480.2114@nanos

arch/powerpc/kernel/watchdog.c

@@ -355,19 +355,24 @@ static void watchdog_calc_timeouts(void)
 	wd_timer_period_ms = watchdog_thresh * 1000 * 2 / 5;
 }
 
-void watchdog_nmi_reconfigure(bool run)
+void watchdog_nmi_stop(void)
 {
 	int cpu;
 
 	cpus_read_lock();
-	if (!run) {
-		for_each_cpu(cpu, &wd_cpus_enabled)
-			stop_wd_on_cpu(cpu);
-	} else {
-		watchdog_calc_timeouts();
-		for_each_cpu_and(cpu, cpu_online_mask, &watchdog_cpumask)
-			start_wd_on_cpu(cpu);
-	}
+	for_each_cpu(cpu, &wd_cpus_enabled)
+		stop_wd_on_cpu(cpu);
+	cpus_read_unlock();
+}
+
+void watchdog_nmi_start(void)
+{
+	int cpu;
+
+	cpus_read_lock();
+	watchdog_calc_timeouts();
+	for_each_cpu_and(cpu, cpu_online_mask, &watchdog_cpumask)
+		start_wd_on_cpu(cpu);
 	cpus_read_unlock();
 }
 

include/linux/nmi.h

@@ -109,7 +109,8 @@ static inline int hardlockup_detector_perf_init(void) { return 0; }
 # endif
 #endif
 
-void watchdog_nmi_reconfigure(bool run);
+void watchdog_nmi_stop(void);
+void watchdog_nmi_start(void);
 
 /**
  * touch_nmi_watchdog - restart NMI watchdog timeout.

kernel/watchdog.c

@@ -123,24 +123,27 @@ int __weak __init watchdog_nmi_probe(void)
 }
 
 /**
- * watchdog_nmi_reconfigure - Optional function to reconfigure NMI watchdogs
- * @run:	If false stop the watchdogs on all enabled CPUs
- *		If true start the watchdogs on all enabled CPUs
+ * watchdog_nmi_stop - Stop the watchdog for reconfiguration
  *
- * The core call order is:
- * watchdog_nmi_reconfigure(false);
+ * The reconfiguration steps are:
+ * watchdog_nmi_stop();
  * update_variables();
- * watchdog_nmi_reconfigure(true);
+ * watchdog_nmi_start();
+ */
+void __weak watchdog_nmi_stop(void) { }
+
+/**
+ * watchdog_nmi_start - Start the watchdog after reconfiguration
  *
- * The second call which starts the watchdogs again guarantees that the
- * following variables are stable across the call.
+ * Counterpart to watchdog_nmi_stop().
+ *
+ * The following variables have been updated in update_variables() and
+ * contain the currently valid configuration:
  * - watchdog_enabled
  * - watchdog_thresh
  * - watchdog_cpumask
- *
- * After the call the variables can be changed again.
  */
-void __weak watchdog_nmi_reconfigure(bool run) { }
+void __weak watchdog_nmi_start(void) { }
 
 /**
  * lockup_detector_update_enable - Update the sysctl enable bit
@@ -551,13 +554,13 @@ static void softlockup_unpark_threads(void)
 
 static void softlockup_reconfigure_threads(void)
 {
-	watchdog_nmi_reconfigure(false);
+	watchdog_nmi_stop();
 	softlockup_park_all_threads();
 	set_sample_period();
 	lockup_detector_update_enable();
 	if (watchdog_enabled && watchdog_thresh)
 		softlockup_unpark_threads();
-	watchdog_nmi_reconfigure(true);
+	watchdog_nmi_start();
 }
 
 /*
@@ -602,9 +605,9 @@ static inline void watchdog_disable_all_cpus(void) { }
 static inline void softlockup_init_threads(void) { }
 static void softlockup_reconfigure_threads(void)
 {
-	watchdog_nmi_reconfigure(false);
+	watchdog_nmi_stop();
 	lockup_detector_update_enable();
-	watchdog_nmi_reconfigure(true);
+	watchdog_nmi_start();
 }
 #endif /* !CONFIG_SOFTLOCKUP_DETECTOR */