Commit f1c39625 authored Aug 24, 2011 by Jeremy Fitzhardinge

xen: use non-tracing preempt in xen_clocksource_read()



The tracing code used sched_clock() to get tracing timestamps, which
ends up calling xen_clocksource_read().  xen_clocksource_read() must
disable preemption, but if preemption tracing is enabled, this results
in infinite recursion.

I've only noticed this when boot-time tracing tests are enabled, but it
seems like a generic bug.  It looks like it would also affect
kvm_clocksource_read().

Reported-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>

parent fcb8ce5c

arch/x86/xen/time.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -168,9 +168,10 @@ cycle_t xen_clocksource_read(void)
		struct pvclock_vcpu_time_info *src;
		cycle_t ret;

		src = &get_cpu_var(xen_vcpu)->time;
		preempt_disable_notrace();
		src = &__get_cpu_var(xen_vcpu)->time;
		ret = pvclock_clocksource_read(src);
		put_cpu_var(xen_vcpu);
		preempt_enable_notrace();
		return ret;
		}

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