[PATCH v2] clk: Don't hold prepare_lock across debugfs creation

[sboyd@codeaurora.org (Stephen Boyd)]

On 09/04, Stephen Boyd wrote:
> 
> I don't understand why we need to hold the prepare lock around
> the kref_put(), so I changed the flow so that we don't do this
> when we unregister a clock.

Ok we hold the prepare mutex to make sure get and put are serialized.
Good. Here's the interdiff to move the debugfs unregistration before
the prepare lock and detect double unregisters without holding
the prepare lock.

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 3c04d0d69b96..8ca28189e4e9 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -338,10 +338,14 @@ unlock:
 static void clk_debug_unregister(struct clk *clk)
 {
 	mutex_lock(&clk_debug_lock);
-	hlist_del_init(&clk->debug_node);
-	mutex_unlock(&clk_debug_lock);
+	if (!clk->dentry)
+		goto out;
 
+	hlist_del_init(&clk->debug_node);
 	debugfs_remove_recursive(clk->dentry);
+	clk->dentry = NULL;
+out:
+	mutex_unlock(&clk_debug_lock);
 }
 
 struct dentry *clk_debugfs_add_file(struct clk *clk, char *name, umode_t mode,
@@ -2065,14 +2069,15 @@ void clk_unregister(struct clk *clk)
 {
 	unsigned long flags;
 
-       if (!clk || WARN_ON_ONCE(IS_ERR(clk)))
-               return;
+	if (!clk || WARN_ON_ONCE(IS_ERR(clk)))
+		return;
+
+	clk_debug_unregister(clk);
 
 	clk_prepare_lock();
 
 	if (clk->ops == &clk_nodrv_ops) {
 		pr_err("%s: unregistered clock: %s\n", __func__, clk->name);
-		clk_prepare_unlock();
 		return;
 	}
 	/*
@@ -2097,11 +2102,9 @@ void clk_unregister(struct clk *clk)
 	if (clk->prepare_count)
 		pr_warn("%s: unregistering prepared clock: %s\n",
 					__func__, clk->name);
-	clk_prepare_unlock();
-
-	clk_debug_unregister(clk);
-
 	kref_put(&clk->ref, __clk_release);
+
+	clk_prepare_unlock();
 }
 EXPORT_SYMBOL_GPL(clk_unregister);
 
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