1 files changed, 76 insertions, 24 deletions

diff --git a/drivers/xen/evtchn.c b/drivers/xen/evtchn.c
index fec6ba3c08a8..ef11daf0cafe 100644
--- a/drivers/xen/evtchn.c
+++ b/drivers/xen/evtchn.c
@@ -69,20 +69,51 @@ struct per_user_data {
         const char *name;
 };
 
-/* Who's bound to each port? */
-static struct per_user_data *port_user[NR_EVENT_CHANNELS];
+/*
+ * Who's bound to each port?  This is logically an array of struct
+ * per_user_data *, but we encode the current enabled-state in bit 0.
+ */
+static unsigned long *port_user;
 static DEFINE_SPINLOCK(port_user_lock); /* protects port_user[] and ring_prod */
 
-irqreturn_t evtchn_interrupt(int irq, void *data)
+static inline struct per_user_data *get_port_user(unsigned port)
+{
+        return (struct per_user_data *)(port_user[port] & ~1);
+}
+
+static inline void set_port_user(unsigned port, struct per_user_data *u)
+{
+        port_user[port] = (unsigned long)u;
+}
+
+static inline bool get_port_enabled(unsigned port)
+{
+        return port_user[port] & 1;
+}
+
+static inline void set_port_enabled(unsigned port, bool enabled)
+{
+        if (enabled)
+                port_user[port] |= 1;
+        else
+                port_user[port] &= ~1;
+}
+
+static irqreturn_t evtchn_interrupt(int irq, void *data)
 {
         unsigned int port = (unsigned long)data;
         struct per_user_data *u;
 
         spin_lock(&port_user_lock);
 
-        u = port_user[port];
+        u = get_port_user(port);
+
+        WARN(!get_port_enabled(port),
+             "Interrupt for port %d, but apparently not enabled; per-user %p\n",
+             port, u);
 
         disable_irq_nosync(irq);
+        set_port_enabled(port, false);
 
         if ((u->ring_prod - u->ring_cons) < EVTCHN_RING_SIZE) {
                 u->ring[EVTCHN_RING_MASK(u->ring_prod)] = port;
@@ -92,9 +123,8 @@ irqreturn_t evtchn_interrupt(int irq, void *data)
                         kill_fasync(&u->evtchn_async_queue,
                                     SIGIO, POLL_IN);
                 }
-        } else {
+        } else
                 u->ring_overflow = 1;
-        }
 
         spin_unlock(&port_user_lock);
 
@@ -198,9 +228,18 @@ static ssize_t evtchn_write(struct file *file, const char __user *buf,
                 goto out;
 
         spin_lock_irq(&port_user_lock);
-        for (i = 0; i < (count/sizeof(evtchn_port_t)); i++)
-                if ((kbuf[i] < NR_EVENT_CHANNELS) && (port_user[kbuf[i]] == u))
-                        enable_irq(irq_from_evtchn(kbuf[i]));
+
+        for (i = 0; i < (count/sizeof(evtchn_port_t)); i++) {
+                unsigned port = kbuf[i];
+
+                if (port < NR_EVENT_CHANNELS &&
+                    get_port_user(port) == u &&
+                    !get_port_enabled(port)) {
+                        set_port_enabled(port, true);
+                        enable_irq(irq_from_evtchn(port));
+                }
+        }
+
         spin_unlock_irq(&port_user_lock);
 
         rc = count;
@@ -222,8 +261,9 @@ static int evtchn_bind_to_user(struct per_user_data *u, int port)
          * interrupt handler yet, and our caller has already
          * serialized bind operations.)
          */
-        BUG_ON(port_user[port] != NULL);
-        port_user[port] = u;
+        BUG_ON(get_port_user(port) != NULL);
+        set_port_user(port, u);
+        set_port_enabled(port, true); /* start enabled */
 
         rc = bind_evtchn_to_irqhandler(port, evtchn_interrupt, IRQF_DISABLED,
                                        u->name, (void *)(unsigned long)port);
@@ -239,10 +279,7 @@ static void evtchn_unbind_from_user(struct per_user_data *u, int port)
 
         unbind_from_irqhandler(irq, (void *)(unsigned long)port);
 
-        /* make sure we unbind the irq handler before clearing the port */
-        barrier();
-
-        port_user[port] = NULL;
+        set_port_user(port, NULL);
 }
 
 static long evtchn_ioctl(struct file *file,
@@ -333,15 +370,17 @@ static long evtchn_ioctl(struct file *file,
                 spin_lock_irq(&port_user_lock);
 
                 rc = -ENOTCONN;
-                if (port_user[unbind.port] != u) {
+                if (get_port_user(unbind.port) != u) {
                         spin_unlock_irq(&port_user_lock);
                         break;
                 }
 
-                evtchn_unbind_from_user(u, unbind.port);
+                disable_irq(irq_from_evtchn(unbind.port));
 
                 spin_unlock_irq(&port_user_lock);
 
+                evtchn_unbind_from_user(u, unbind.port);
+
                 rc = 0;
                 break;
         }
@@ -355,7 +394,7 @@ static long evtchn_ioctl(struct file *file,
 
                 if (notify.port >= NR_EVENT_CHANNELS) {
                         rc = -EINVAL;
-                } else if (port_user[notify.port] != u) {
+                } else if (get_port_user(notify.port) != u) {
                         rc = -ENOTCONN;
                 } else {
                         notify_remote_via_evtchn(notify.port);
@@ -431,7 +470,7 @@ static int evtchn_open(struct inode *inode, struct file *filp)
 
         filp->private_data = u;
 
-        return 0;
+        return nonseekable_open(inode, filp);;
 }
 
 static int evtchn_release(struct inode *inode, struct file *filp)
@@ -444,14 +483,21 @@ static int evtchn_release(struct inode *inode, struct file *filp)
         free_page((unsigned long)u->ring);
 
         for (i = 0; i < NR_EVENT_CHANNELS; i++) {
-                if (port_user[i] != u)
+                if (get_port_user(i) != u)
                         continue;
 
-                evtchn_unbind_from_user(port_user[i], i);
+                disable_irq(irq_from_evtchn(i));
         }
 
         spin_unlock_irq(&port_user_lock);
 
+        for (i = 0; i < NR_EVENT_CHANNELS; i++) {
+                if (get_port_user(i) != u)
+                        continue;
+
+                evtchn_unbind_from_user(get_port_user(i), i);
+        }
+
         kfree(u->name);
         kfree(u);
 
@@ -467,12 +513,12 @@ static const struct file_operations evtchn_fops = {
         .fasync  = evtchn_fasync,
         .open    = evtchn_open,
         .release = evtchn_release,
-        .llseek = noop_llseek,
+        .llseek  = no_llseek,
 };
 
 static struct miscdevice evtchn_miscdev = {
         .minor        = MISC_DYNAMIC_MINOR,
-        .name         = "evtchn",
+        .name         = "xen/evtchn",
         .fops         = &evtchn_fops,
 };
 static int __init evtchn_init(void)
@@ -482,8 +528,11 @@ static int __init evtchn_init(void)
         if (!xen_domain())
                 return -ENODEV;
 
+        port_user = kcalloc(NR_EVENT_CHANNELS, sizeof(*port_user), GFP_KERNEL);
+        if (port_user == NULL)
+                return -ENOMEM;
+
         spin_lock_init(&port_user_lock);
-        memset(port_user, 0, sizeof(port_user));
 
         /* Create '/dev/misc/evtchn'. */
         err = misc_register(&evtchn_miscdev);
@@ -499,6 +548,9 @@ static int __init evtchn_init(void)
 
 static void __exit evtchn_cleanup(void)
 {
+        kfree(port_user);
+        port_user = NULL;
+
         misc_deregister(&evtchn_miscdev);
 }