From b16005f3882be8c9ef98c0b96c19535f6f9dcaa2 Mon Sep 17 00:00:00 2001
From: Jeremy Fitzhardinge <jeremy@goop.org>
Date: Mon, 17 Mar 2008 16:37:20 -0700
Subject: [PATCH] --- yaml --- r: 93161 b: refs/heads/master c:
 229664bee6126e01f8662976a5fe2e79813b77c8 h: refs/heads/master i:   93159:
 d5a8cc6dfebebe3e2b134f9399ea6703bb3538e5 v: v3

---
 [refs]                      |  2 +-
 trunk/arch/x86/xen/events.c | 46 ++++++++++++++++++++++++-------------
 2 files changed, 31 insertions(+), 17 deletions(-)

diff --git a/[refs] b/[refs]
index ce4a79bc9a55..a0ddfa24008d 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: ee8fa1c67f0b873a324960f0ca9fa1d7e49aa86b
+refs/heads/master: 229664bee6126e01f8662976a5fe2e79813b77c8
diff --git a/trunk/arch/x86/xen/events.c b/trunk/arch/x86/xen/events.c
index f73b53bd65b7..85bac298b3cb 100644
--- a/trunk/arch/x86/xen/events.c
+++ b/trunk/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();
 }