[Xen-devel] [PATCH] mini-os: select call incorrectly reports xce_handle as ready

[Diego Ongaro <diego.ongaro@xxxxxxxxxx>]

The current implementation in minios of xc_evtchn_pending doesn't set
read=0 when there is exactly one port pending. This resulted in select()
incorrectly reporting the file descriptor as ready.

Signed-off-by: Diego Ongaro <diego.ongaro@xxxxxxxxxx>
Signed-off-by: Samuel Thibault <samuel.thibault@xxxxxxxxxxxxx>
---
diff --git a/tools/libxc/xc_minios.c b/tools/libxc/xc_minios.c
--- a/tools/libxc/xc_minios.c
+++ b/tools/libxc/xc_minios.c
@@ -287,22 +287,28 @@
 
 evtchn_port_or_error_t xc_evtchn_pending(int xce_handle)
 {
     int i;
     unsigned long flags;
+    evtchn_port_t ret = -1;
+
     local_irq_save(flags);
+    files[xce_handle].read = 0;
     for (i = 0; i < MAX_EVTCHN_PORTS; i++) {
-       evtchn_port_t port = files[xce_handle].evtchn.ports[i].port;
-       if (port != -1 && files[xce_handle].evtchn.ports[i].pending) {
-           files[xce_handle].evtchn.ports[i].pending = 0;
-           local_irq_restore(flags);
-           return port;
-       }
+        evtchn_port_t port = files[xce_handle].evtchn.ports[i].port;
+        if (port != -1 && files[xce_handle].evtchn.ports[i].pending) {
+            if (ret == -1) {
+                ret = port;
+                files[xce_handle].evtchn.ports[i].pending = 0;
+            } else {
+                files[xce_handle].read = 1;
+                break;
+            }
+        }
     }
-    files[xce_handle].read = 0;
     local_irq_restore(flags);
-    return -1;
+    return ret;
 }
 
 int xc_evtchn_unmask(int xce_handle, evtchn_port_t port)
 {
     unmask_evtchn(port);

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