From f1c39625d63c9f8eba8f036429c10a9cb9e32920 Mon Sep 17 00:00:00 2001 From: Jeremy Fitzhardinge Date: Wed, 24 Aug 2011 09:54:24 -0700 Subject: [PATCH] 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 Signed-off-by: Jeremy Fitzhardinge Cc: Avi Kivity Cc: Marcelo Tosatti --- arch/x86/xen/time.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c index 5158c505bef9..163b4679556e 100644 --- a/arch/x86/xen/time.c +++ b/arch/x86/xen/time.c @@ -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; }