[Xen-changelog] [linux-2.6.18-xen] linux/x86: fix long timeout handling in stop_hz_timer()

["Xen patchbot-linux-2.6.18-xen" <patchbot-linux-2.6.18-xen@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1266832998 0
# Node ID ff275dae07eecb5bbcd99cc0f8cb9fd41d400145
# Parent  05a04247f0576a71dc4d897d0b03cbfd4c2ed57b
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@xxxxxxxxxx>
---
 arch/i386/kernel/time-xen.c |   17 +++++++++++++++--
 1 files changed, 15 insertions(+), 2 deletions(-)

diff -r 05a04247f057 -r ff275dae07ee arch/i386/kernel/time-xen.c
--- a/arch/i386/kernel/time-xen.c       Mon Feb 15 17:44:01 2010 +0000
+++ b/arch/i386/kernel/time-xen.c       Mon Feb 22 10:03:18 2010 +0000
@@ -1022,7 +1022,10 @@ 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
@@ -1036,7 +1039,17 @@ 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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