xen: short-cut for recursive event handling

[karo-tx-linux.git] / arch / x86 / xen / events.c

diff --git a/arch/x86/xen/events.c b/arch/x86/xen/events.c
index f73b53bd65b76991b0e53015a261a9657ce23a4c..85bac298b3cb901240276959d5bd4f6e3a065947 100644 (file)
--- a/arch/x86/xen/events.c
+++ b/arch/x86/xen/events.c
@@ -517,29 +517,43 @@ void xen_evtchn_do_upcall(struct pt_regs *regs)
        int cpu = get_cpu();
        struct shared_info *s = HYPERVISOR_shared_info;
        struct vcpu_info *vcpu_info = __get_cpu_var(xen_vcpu);
-       unsigned long pending_words;
+       static DEFINE_PER_CPU(unsigned, nesting_count);
+       unsigned count;
 
-       vcpu_info->evtchn_upcall_pending = 0;
+       do {
+               unsigned long pending_words;
 
-       /* NB. No need for a barrier here -- XCHG is a barrier on x86. */
-       pending_words = xchg(&vcpu_info->evtchn_pending_sel, 0);
-       while (pending_words != 0) {
-               unsigned long pending_bits;
-               int word_idx = __ffs(pending_words);
-               pending_words &= ~(1UL << word_idx);
+               vcpu_info->evtchn_upcall_pending = 0;
 
-               while ((pending_bits = active_evtchns(cpu, s, word_idx)) != 0) {
-                       int bit_idx = __ffs(pending_bits);
-                       int port = (word_idx * BITS_PER_LONG) + bit_idx;
-                       int irq = evtchn_to_irq[port];
+               if (__get_cpu_var(nesting_count)++)
+                       goto out;
 
-                       if (irq != -1) {
-                               regs->orig_ax = ~irq;
-                               do_IRQ(regs);
+               /* NB. No need for a barrier here -- XCHG is a barrier on x86. */
+               pending_words = xchg(&vcpu_info->evtchn_pending_sel, 0);
+               while (pending_words != 0) {
+                       unsigned long pending_bits;
+                       int word_idx = __ffs(pending_words);
+                       pending_words &= ~(1UL << word_idx);
+
+                       while ((pending_bits = active_evtchns(cpu, s, word_idx)) != 0) {
+                               int bit_idx = __ffs(pending_bits);
+                               int port = (word_idx * BITS_PER_LONG) + bit_idx;
+                               int irq = evtchn_to_irq[port];
+
+                               if (irq != -1) {
+                                       regs->orig_ax = ~irq;
+                                       do_IRQ(regs);
+                               }
                        }
                }
-       }
 
+               BUG_ON(!irqs_disabled());
+
+               count = __get_cpu_var(nesting_count);
+               __get_cpu_var(nesting_count) = 0;
+       } while(count != 1);
+
+out:
        put_cpu();
 }