xen/evtchn: track enabled state for each port

enable/disable_irq() complain if the enables/disables are unbalanced,
so keep track of the state and avoid redundant enables.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

1 files changed, 56 insertions, 15 deletions

diff --git a/drivers/xen/evtchn.c b/drivers/xen/evtchn.c
index af031950f9b1..4356a9a030df 100644
--- a/drivers/xen/evtchn.c
+++ b/drivers/xen/evtchn.c
@@ -69,10 +69,36 @@ 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[NR_EVENT_CHANNELS];
 static DEFINE_SPINLOCK(port_user_lock); /* protects port_user[] and ring_prod */
 
+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;
+}
+
 irqreturn_t evtchn_interrupt(int irq, void *data)
 {
         unsigned int port = (unsigned long)data;
@@ -80,9 +106,15 @@ irqreturn_t evtchn_interrupt(int irq, void *data)
 
         spin_lock(&port_user_lock);
 
-        u = port_user[port];
+        u = get_port_user(port);
+
+        if (WARN(!get_port_enabled(port),
+                 "Interrupt for port %d, but apparently not enabled; per-user %p\n",
+                 port, u))
+                goto out;
 
         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;
@@ -92,10 +124,10 @@ irqreturn_t evtchn_interrupt(int irq, void *data)
                         kill_fasync(&u->evtchn_async_queue,
                                     SIGIO, POLL_IN);
                 }
-        } else {
+        } else
                 u->ring_overflow = 1;
-        }
 
+out:
         spin_unlock(&port_user_lock);
 
         return IRQ_HANDLED;
@@ -198,9 +230,18 @@ 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 +263,8 @@ 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);
 
         rc = bind_evtchn_to_irqhandler(port, evtchn_interrupt, IRQF_DISABLED,
                                        u->name, (void *)(unsigned long)port);
@@ -242,7 +283,7 @@ static void evtchn_unbind_from_user(struct per_user_data *u, int 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,
@@ -333,7 +374,7 @@ 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;
                 }
@@ -355,7 +396,7 @@ 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);
@@ -444,10 +485,10 @@ 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);
+                evtchn_unbind_from_user(get_port_user(i), i);
         }
 
         spin_unlock_irq(&port_user_lock);