Xen devel - Feb 2010 - [PATCH] linux/x86: fix long timeout handling in stop_hz_timer()

Other than for HYPERVISOR_set_timer_op, zero doesn''t mean "no
timeout"
for VCPUOP_set_singleshot_timer (but should be retained rather than
adjusted by NS_PER_TICK/2 for the former).

Also properly cancel the singleshot timer is start_hz_timer().

Signed-off-by: Jan Beulich <jbeulich@novell.com>

--- a/arch/i386/kernel/time-xen.c
+++ b/arch/i386/kernel/time-xen.c
@@ -939,7 +939,10 @@ static void stop_hz_timer(void)
 		j = jiffies + 1;
 	}
 
-	singleshot.timeout_abs_ns = jiffies_to_st(j) + NS_PER_TICK/2;
+	singleshot.timeout_abs_ns = jiffies_to_st(j);
+	if (!singleshot.timeout_abs_ns)
+		return;
+	singleshot.timeout_abs_ns += NS_PER_TICK / 2;
 	singleshot.flags = 0;
 	rc = HYPERVISOR_vcpu_op(VCPUOP_set_singleshot_timer, cpu, &singleshot);
 #if CONFIG_XEN_COMPAT <= 0x030004
@@ -953,7 +956,17 @@ static void stop_hz_timer(void)
 
 static void start_hz_timer(void)
 {
-	cpu_clear(smp_processor_id(), nohz_cpu_mask);
+	unsigned int cpu = smp_processor_id();
+	int rc = HYPERVISOR_vcpu_op(VCPUOP_stop_singleshot_timer, cpu, NULL);
+
+#if CONFIG_XEN_COMPAT <= 0x030004
+	if (rc) {
+		BUG_ON(rc != -ENOSYS);
+		rc = HYPERVISOR_set_timer_op(0);
+	}
+#endif
+	BUG_ON(rc);
+	cpu_clear(cpu, nohz_cpu_mask);
 }
 
 void raw_safe_halt(void)




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