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authorAvi Kivity <avi@redhat.com>2011-11-15 14:59:07 +0200
committerAvi Kivity <avi@redhat.com>2011-11-20 10:53:48 +0200
commit95ef1e52922cf75b1ea2eae54ef886f2cc47eecb (patch)
tree158082c19666aa589b539f20b4cf29e99f205f4f /arch
parentbb75c627fb0dfb8c0ab75d3033709ff928896e16 (diff)
KVM guest: prevent tracing recursion with kvmclock
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 <gleb@redhat.com> Acked-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Avi Kivity <avi@redhat.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kernel/kvmclock.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index c1a0188e29ae..44842d756b29 100644
--- 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;
}