watchdog/core, powerpc: Make watchdog_nmi_reconfigure() two stage

Both the perf reconfiguration and the powerpc watchdog_nmi_reconfigure()
need to be done in two steps.

     1) Stop all NMIs
     2) Read the new parameters and start NMIs

Right now watchdog_nmi_reconfigure() is a combination of both. To allow a
clean reconfiguration add a 'run' argument and split the functionality in
powerpc.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Don Zickus <dzickus@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Cc: linuxppc-dev@lists.ozlabs.org
Link: http://lkml.kernel.org/r/20170912194147.862865570@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c
index 5ded171f02d6b037cd980b7fb26087314d5a604c..291af79a98263e023ef4e2dd0642a04e027b4333 100644 (file)
--- a/arch/powerpc/kernel/watchdog.c
+++ b/arch/powerpc/kernel/watchdog.c
@@ -355,17 +355,18 @@ static void watchdog_calc_timeouts(void)
        wd_timer_period_ms = watchdog_thresh * 1000 * 2 / 5;
 }
 
-void watchdog_nmi_reconfigure(void)
+void watchdog_nmi_reconfigure(bool run)
 {
        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);
+       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);
+       }
 }
 
 /*

diff --git a/include/linux/nmi.h b/include/linux/nmi.h
index 4a8d1037364ef9d8ef23461e80bdc35439ea28b2..eee255bc0fd6239dc7bcec2c1591d0006544d450 100644 (file)
--- a/include/linux/nmi.h
+++ b/include/linux/nmi.h
@@ -103,6 +103,8 @@ static inline void arch_touch_nmi_watchdog(void) {}
 #endif
 #endif
 
+void watchdog_nmi_reconfigure(bool run);
+
 /**
  * touch_nmi_watchdog - restart NMI watchdog timeout.
  *

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index baae9fc950312fe22c230e75760be1b14b2f461e..5693afd2b8eaea482b2ab7715d10b3e3290f5dbe 100644 (file)
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -112,17 +112,25 @@ void __weak watchdog_nmi_disable(unsigned int cpu)
        hardlockup_detector_perf_disable();
 }
 
-/*
- * watchdog_nmi_reconfigure can be implemented to be notified after any
- * watchdog configuration change. The arch hardlockup watchdog should
- * respond to the following variables:
+/**
+ * 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
+ *
+ * The core call order is:
+ * watchdog_nmi_reconfigure(false);
+ * update_variables();
+ * watchdog_nmi_reconfigure(true);
+ *
+ * The second call which starts the watchdogs again guarantees that the
+ * following variables are stable across the call.
  * - watchdog_enabled
  * - watchdog_thresh
  * - watchdog_cpumask
- * - sysctl_hardlockup_all_cpu_backtrace
- * - hardlockup_panic
+ *
+ * After the call the variables can be changed again.
  */
-void __weak watchdog_nmi_reconfigure(void) { }
+void __weak watchdog_nmi_reconfigure(bool run) { }
 
 #ifdef CONFIG_SOFTLOCKUP_DETECTOR
 
@@ -515,10 +523,12 @@ static void softlockup_unpark_threads(void)
 
 static void softlockup_reconfigure_threads(bool enabled)
 {
+       watchdog_nmi_reconfigure(false);
        softlockup_park_all_threads();
        set_sample_period();
        if (enabled)
                softlockup_unpark_threads();
+       watchdog_nmi_reconfigure(true);
 }
 
 /*
@@ -559,7 +569,11 @@ static inline void watchdog_unpark_threads(void) { }
 static inline int watchdog_enable_all_cpus(void) { return 0; }
 static inline void watchdog_disable_all_cpus(void) { }
 static inline void softlockup_init_threads(void) { }
-static inline void softlockup_reconfigure_threads(bool enabled) { }
+static void softlockup_reconfigure_threads(bool enabled)
+{
+       watchdog_nmi_reconfigure(false);
+       watchdog_nmi_reconfigure(true);
+}
 #endif /* !CONFIG_SOFTLOCKUP_DETECTOR */
 
 static void __lockup_detector_cleanup(void)
@@ -599,7 +613,6 @@ static void proc_watchdog_update(void)
        /* Remove impossible cpus to keep sysctl output clean. */
        cpumask_and(&watchdog_cpumask, &watchdog_cpumask, cpu_possible_mask);
        softlockup_reconfigure_threads(watchdog_enabled && watchdog_thresh);
-       watchdog_nmi_reconfigure();
 }
 
 /*