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

Marcelo Tosatti
2013-10-08T01:05:17Z

[-- Attachment #1: 02-kvmclock-touch-watchdog-on-kvmclock-read --]
[-- Type: text/plain, Size: 2260 bytes --]

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@redhat.com>

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.