diff options
Diffstat (limited to 'arch/x86/xen/irq.c')
| -rw-r--r-- | arch/x86/xen/irq.c | 25 |
1 files changed, 12 insertions, 13 deletions
diff --git a/arch/x86/xen/irq.c b/arch/x86/xen/irq.c index 01a4dc015ae..0da7f863056 100644 --- a/arch/x86/xen/irq.c +++ b/arch/x86/xen/irq.c @@ -47,23 +47,18 @@ static void xen_restore_fl(unsigned long flags) /* convert from IF type flag */ flags = !(flags & X86_EFLAGS_IF); - /* There's a one instruction preempt window here. We need to - make sure we're don't switch CPUs between getting the vcpu - pointer and updating the mask. */ + /* See xen_irq_enable() for why preemption must be disabled. */ preempt_disable(); vcpu = this_cpu_read(xen_vcpu); vcpu->evtchn_upcall_mask = flags; - preempt_enable_no_resched(); - - /* Doesn't matter if we get preempted here, because any - pending event will get dealt with anyway. */ if (flags == 0) { - preempt_check_resched(); barrier(); /* unmask then check (avoid races) */ if (unlikely(vcpu->evtchn_upcall_pending)) xen_force_evtchn_callback(); - } + preempt_enable(); + } else + preempt_enable_no_resched(); } PV_CALLEE_SAVE_REGS_THUNK(xen_restore_fl); @@ -82,10 +77,12 @@ static void xen_irq_enable(void) { struct vcpu_info *vcpu; - /* We don't need to worry about being preempted here, since - either a) interrupts are disabled, so no preemption, or b) - the caller is confused and is trying to re-enable interrupts - on an indeterminate processor. */ + /* + * We may be preempted as soon as vcpu->evtchn_upcall_mask is + * cleared, so disable preemption to ensure we check for + * events on the VCPU we are still running on. + */ + preempt_disable(); vcpu = this_cpu_read(xen_vcpu); vcpu->evtchn_upcall_mask = 0; @@ -96,6 +93,8 @@ static void xen_irq_enable(void) barrier(); /* unmask then check (avoid races) */ if (unlikely(vcpu->evtchn_upcall_pending)) xen_force_evtchn_callback(); + + preempt_enable(); } PV_CALLEE_SAVE_REGS_THUNK(xen_irq_enable); |