# HG changeset patch
# User yamahata@xxxxxxxxxxxxx
# Node ID d128d12ca992b6d0dc8b5577de2fbc4299bfcfd0
# Parent  ae245d35457b03f680b994437bd25532b98aa523
evtchn_do_upcall() has a micro optimization which is depends on
that xchg is a barrier.
However xchg of IA64 has acquire semantics so that event
channel notification is lost sometimes. This patch fixes it.
PATCHNAME: memory_barrier_evtchn_do_upcall

Signed-off-by: Isaku Yamahata <yamahata@xxxxxxxxxxxxx>

diff -r ae245d35457b -r d128d12ca992 linux-2.6-xen-sparse/drivers/xen/core/evtchn.c
--- a/linux-2.6-xen-sparse/drivers/xen/core/evtchn.c	Wed Jun 28 13:59:29 2006 +0100
+++ b/linux-2.6-xen-sparse/drivers/xen/core/evtchn.c	Thu Jun 29 14:40:04 2006 +0900
@@ -217,9 +217,8 @@ asmlinkage void evtchn_do_upcall(struct 
 	shared_info_t *s = HYPERVISOR_shared_info;
 	vcpu_info_t   *vcpu_info = &s->vcpu_info[cpu];
 
-	vcpu_info->evtchn_upcall_pending = 0;
-
-	/* NB. No need for a barrier here -- XCHG is a barrier on x86. */
+	evtchn_clear_upcall_pending(vcpu_info);
+
 	l1 = xchg(&vcpu_info->evtchn_pending_sel, 0);
 	while (l1 != 0) {
 		l1i = __ffs(l1);
diff -r ae245d35457b -r d128d12ca992 linux-2.6-xen-sparse/include/asm-i386/mach-xen/asm/hypervisor.h
--- a/linux-2.6-xen-sparse/include/asm-i386/mach-xen/asm/hypervisor.h	Wed Jun 28 13:59:29 2006 +0100
+++ b/linux-2.6-xen-sparse/include/asm-i386/mach-xen/asm/hypervisor.h	Thu Jun 29 14:40:04 2006 +0900
@@ -63,6 +63,14 @@ extern start_info_t *xen_start_info;
 /* Force a proper event-channel callback from Xen. */
 void force_evtchn_callback(void);
 
+/* evtchn_do_upcall() in drivers/xen/core/evtchn.c */
+static inline void
+evtchn_clear_upcall_pending(vcpu_info_t* vcpu_info)
+{
+	vcpu_info->evtchn_upcall_pending = 0;
+	/* NB. No need for a barrier here -- XCHG is a barrier on x86. */
+}
+
 /* arch/xen/kernel/process.c */
 void xen_cpu_idle (void);
 
diff -r ae245d35457b -r d128d12ca992 linux-2.6-xen-sparse/include/asm-ia64/hypervisor.h
--- a/linux-2.6-xen-sparse/include/asm-ia64/hypervisor.h	Wed Jun 28 13:59:29 2006 +0100
+++ b/linux-2.6-xen-sparse/include/asm-ia64/hypervisor.h	Thu Jun 29 14:40:04 2006 +0900
@@ -61,6 +61,13 @@ extern start_info_t *xen_start_info;
 
 void force_evtchn_callback(void);
 
+/* evtchn_do_upcall() in drivers/xen/core/evtchn.c */
+static inline void
+evtchn_clear_upcall_pending(vcpu_info_t* vcpu_info)
+{
+	clear_bit(0, &vcpu_info->evtchn_upcall_pending);
+}
+
 /* Turn jiffies into Xen system time. XXX Implement me. */
 #define jiffies_to_st(j)	0