3.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Avi Kivity <a...@redhat.com>
(cherry picked from commit 95ef1e52922cf75b1ea2eae54ef886f2cc47eecb)
Prevent tracing of preempt_disable() in get_cpu_var() in
kvm_clock_read(). When CONFIG_DEBUG_PREEMPT is enabled,
preempt_disable/enable() are traced and this causes the function_graph
tracer to go into an infinite recursion. By open coding the
preempt_disable() around the get_cpu_var(), we can use the notrace
version which prevents preempt_disable/enable() from being traced and
prevents the recursion.
Based on a similar patch for Xen from Jeremy Fitzhardinge.
Tested-by: Gleb Natapov <g...@redhat.com>
Acked-by: Steven Rostedt <rost...@goodmis.org>
Signed-off-by: Avi Kivity <a...@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gre...@suse.de>
---
arch/x86/kernel/kvmclock.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -74,9 +74,10 @@ static cycle_t kvm_clock_read(void)
struct pvclock_vcpu_time_info *src;
cycle_t ret;
- src = &get_cpu_var(hv_clock);
+ preempt_disable_notrace();
+ src = &__get_cpu_var(hv_clock);
ret = pvclock_clocksource_read(src);
- put_cpu_var(hv_clock);
+ preempt_enable_notrace();
return ret;
}
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