[patch V2 22/29] lockup_detector: Make watchdog_nmi_reconfigure() two stage

Thomas Gleixner
2017-09-12T19:52:05Z

[-- Attachment #1: lockup_detector_Make_watchdog_nmi_reconfigure_two_stage.patch --]
[-- Type: text/plain, Size: 4334 bytes --]

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>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linuxppc-dev@lists.ozlabs.org
Link: http://lkml.kernel.org/r/20170831073054.740462115@linutronix.de

---
arch/powerpc/kernel/watchdog.c | 17 +++++++++--------
include/linux/nmi.h | 2 ++
kernel/watchdog.c | 31 ++++++++++++++++++++++---------
3 files changed, 33 insertions(+), 17 deletions(-)

--- 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);
+ }
}

/*
--- a/include/linux/nmi.h
+++ b/include/linux/nmi.h
@@ -103,6 +103,8 @@ static inline void arch_touch_nmi_watchd
#endif
#endif

+void watchdog_nmi_reconfigure(bool run);
+
/**
* touch_nmi_watchdog - restart NMI watchdog timeout.
*
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -112,17 +112,25 @@ void __weak watchdog_nmi_disable(unsigne
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(vo

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_threa
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();
}

/*