[2/4] omap mailbox: prevent multiple concurrent receivers race

Commit Message

Ohad Ben Cohen June 23, 2010, 12:11 a.m. UTC

None

Patch

diff --git a/arch/arm/plat-omap/include/plat/mailbox.h b/arch/arm/plat-omap/include/plat/mailbox.h
index 0b45664..5df35b4 100644
--- a/arch/arm/plat-omap/include/plat/mailbox.h
+++ b/arch/arm/plat-omap/include/plat/mailbox.h
@@ -57,6 +57,7 @@  struct omap_mbox {
 	struct omap_mbox_ops	*ops;
 	struct device		*dev;
 	void			*priv;
+	atomic_t		count;
 };
 
 int omap_mbox_msg_send(struct omap_mbox *, mbox_msg_t msg);
diff --git a/arch/arm/plat-omap/mailbox.c b/arch/arm/plat-omap/mailbox.c
index 14b716d..aafa63f 100644
--- a/arch/arm/plat-omap/mailbox.c
+++ b/arch/arm/plat-omap/mailbox.c
@@ -320,9 +320,17 @@  struct omap_mbox *omap_mbox_get(const char *name, int (*callback)(void *))
 	if (!mbox)
 		return ERR_PTR(-ENOENT);
 
+	if (atomic_inc_return(&mbox->count) > 1) {
+		pr_err("%s: mbox %s already in use\n", __func__, name);
+		atomic_dec(&mbox->count);
+		return ERR_PTR(-EBUSY);
+	}
+
 	ret = omap_mbox_startup(mbox);
-	if (ret)
+	if (ret) {
+		atomic_dec(&mbox->count);
 		return ERR_PTR(-ENODEV);
+	}
 
 	mbox->rxq->callback = callback;
 
@@ -333,6 +341,7 @@  EXPORT_SYMBOL(omap_mbox_get);
 void omap_mbox_put(struct omap_mbox *mbox)
 {
 	omap_mbox_fini(mbox);
+	atomic_dec(&mbox->count);
 }
 EXPORT_SYMBOL(omap_mbox_put);
 
@@ -349,6 +358,7 @@  int omap_mbox_register(struct device *parent, struct omap_mbox **list)
 
 	for (i = 0; mboxes[i]; i++) {
 		struct omap_mbox *mbox = mboxes[i];
+		atomic_set(&mbox->count, 0);
 		mbox->dev = device_create(&omap_mbox_class,
 				parent, 0, mbox, "%s", mbox->name);
 		if (IS_ERR(mbox->dev)) {