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Commit f1c39625 authored by Jeremy Fitzhardinge's avatar Jeremy Fitzhardinge
Browse files

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: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: default avatarJeremy 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;

}