[patch 2/3] pvclock: detect watchdog reset at pvclock read

[Marcelo Tosatti]

Implement reset of kernel watchdogs at pvclock read time. This avoids
adding special code to every watchdog.

This is possible for watchdogs which measure time based on sched_clock() or 
ktime_get() variants.

Suggested by Don Zickus.

Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>

Index: kvm/arch/x86/kernel/kvmclock.c
===================================================================
--- kvm.orig/arch/x86/kernel/kvmclock.c
+++ kvm/arch/x86/kernel/kvmclock.c
@@ -139,6 +139,7 @@ bool kvm_check_and_clear_guest_paused(vo
 	src = &hv_clock[cpu].pvti;
 	if ((src->flags & PVCLOCK_GUEST_STOPPED) != 0) {
 		src->flags &= ~PVCLOCK_GUEST_STOPPED;
+		pvclock_touch_watchdogs();
 		ret = true;
 	}
 
Index: kvm/arch/x86/kernel/pvclock.c
===================================================================
--- kvm.orig/arch/x86/kernel/pvclock.c
+++ kvm/arch/x86/kernel/pvclock.c
@@ -21,6 +21,7 @@
 #include <linux/sched.h>
 #include <linux/gfp.h>
 #include <linux/bootmem.h>
+#include <linux/hung_task.h>
 #include <asm/fixmap.h>
 #include <asm/pvclock.h>
 
@@ -43,6 +44,14 @@ unsigned long pvclock_tsc_khz(struct pvc
 	return pv_tsc_khz;
 }
 
+void pvclock_touch_watchdogs(void)
+{
+	touch_softlockup_watchdog_sync();
+	clocksource_touch_watchdog();
+	rcu_cpu_stall_reset();
+	reset_hung_task_detector();
+}
+
 static atomic64_t last_value = ATOMIC64_INIT(0);
 
 void pvclock_resume(void)
@@ -74,6 +83,11 @@ cycle_t pvclock_clocksource_read(struct
 		version = __pvclock_read_cycles(src, &ret, &flags);
 	} while ((src->version & 1) || version != src->version);
 
+	if (unlikely((flags & PVCLOCK_GUEST_STOPPED) != 0)) {
+		src->flags &= ~PVCLOCK_GUEST_STOPPED;
+		pvclock_touch_watchdogs();
+	}
+
 	if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) &&
 		(flags & PVCLOCK_TSC_STABLE_BIT))
 		return ret;
Index: kvm/arch/x86/include/asm/pvclock.h
===================================================================
--- kvm.orig/arch/x86/include/asm/pvclock.h
+++ kvm/arch/x86/include/asm/pvclock.h
@@ -14,6 +14,8 @@ void pvclock_read_wallclock(struct pvclo
 			    struct timespec *ts);
 void pvclock_resume(void);
 
+void pvclock_touch_watchdogs(void);
+
 /*
  * Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction,
  * yielding a 64-bit result.


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