From: Carsten Otte Date: Wed, 21 May 2008 11:37:44 +0000 (+0200) Subject: KVM: s390: Fix race condition in kvm_s390_handle_wait X-Git-Tag: v2.6.26-rc6~11^2~11 X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=e52b2af541bcb299212a63cfa3e3231618a415be;p=linux-2.6-omap-h63xx.git KVM: s390: Fix race condition in kvm_s390_handle_wait The call to add_timer was issued before local_int.lock was taken and before timer_due was set to 0. If the timer expires before the lock is being taken, the timer function will set timer_due to 1 and exit before the vcpu falls asleep. Depending on other external events, the vcpu might sleep forever. This fix pulls setting timer_due to the beginning of the function before add_timer, which ensures correct behavior. Signed-off-by: Carsten Otte Signed-off-by: Avi Kivity --- diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c index fcd1ed8015c..84a7fed4cd4 100644 --- a/arch/s390/kvm/interrupt.c +++ b/arch/s390/kvm/interrupt.c @@ -339,6 +339,11 @@ int kvm_s390_handle_wait(struct kvm_vcpu *vcpu) if (kvm_cpu_has_interrupt(vcpu)) return 0; + __set_cpu_idle(vcpu); + spin_lock_bh(&vcpu->arch.local_int.lock); + vcpu->arch.local_int.timer_due = 0; + spin_unlock_bh(&vcpu->arch.local_int.lock); + if (psw_interrupts_disabled(vcpu)) { VCPU_EVENT(vcpu, 3, "%s", "disabled wait"); __unset_cpu_idle(vcpu); @@ -366,8 +371,6 @@ int kvm_s390_handle_wait(struct kvm_vcpu *vcpu) no_timer: spin_lock_bh(&vcpu->arch.local_int.float_int->lock); spin_lock_bh(&vcpu->arch.local_int.lock); - __set_cpu_idle(vcpu); - vcpu->arch.local_int.timer_due = 0; add_wait_queue(&vcpu->arch.local_int.wq, &wait); while (list_empty(&vcpu->arch.local_int.list) && list_empty(&vcpu->arch.local_int.float_int->list) &&