linux-kernel - [PATCH 4.0 044/148] clk: add missing lock when call clk_core_enable in clk_set

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Date:	Wed,  3 Jun 2015 21:08:34 +0900
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Mike Turquette <mturquette@...aro.org>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Dong Aisheng <aisheng.dong@...escale.com>
Subject: [PATCH 4.0 044/148] clk: add missing lock when call clk_core_enable in clk_set_parent

4.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dong Aisheng <aisheng.dong@...escale.com>

commit d2a5d46b167a9a8231264daf80165b739aecf1d7 upstream.

Before commit 035a61c314eb ("clk: Make clk API return per-user
struct clk instances") we acquired the enable_lock in
__clk_set_parent_{before,after}() by means of calling
clk_enable(). After commit 035a61c314eb we use clk_core_enable()
in place of the clk_enable(), and clk_core_enable() doesn't
acquire the enable_lock. This opens up a race condition between
clk_set_parent() and clk_enable(). Fix it.

Fixes: 035a61c314eb ("clk: Make clk API return per-user struct clk instances")
Cc: Mike Turquette <mturquette@...aro.org>
Cc: Stephen Boyd <sboyd@...eaurora.org>
Signed-off-by: Dong Aisheng <aisheng.dong@...escale.com>
Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/clk/clk.c |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1443,8 +1443,10 @@ static struct clk_core *__clk_set_parent
 	 */
 	if (clk->prepare_count) {
 		clk_core_prepare(parent);
+		flags = clk_enable_lock();
 		clk_core_enable(parent);
 		clk_core_enable(clk);
+		clk_enable_unlock(flags);
 	}
 
 	/* update the clk tree topology */
@@ -1459,13 +1461,17 @@ static void __clk_set_parent_after(struc
 				   struct clk_core *parent,
 				   struct clk_core *old_parent)
 {
+	unsigned long flags;
+
 	/*
 	 * Finish the migration of prepare state and undo the changes done
 	 * for preventing a race with clk_enable().
 	 */
 	if (core->prepare_count) {
+		flags = clk_enable_lock();
 		clk_core_disable(core);
 		clk_core_disable(old_parent);
+		clk_enable_unlock(flags);
 		clk_core_unprepare(old_parent);
 	}
 }
@@ -1489,8 +1495,10 @@ static int __clk_set_parent(struct clk_c
 		clk_enable_unlock(flags);
 
 		if (clk->prepare_count) {
+			flags = clk_enable_lock();
 			clk_core_disable(clk);
 			clk_core_disable(parent);
+			clk_enable_unlock(flags);
 			clk_core_unprepare(parent);
 		}
 		return ret;


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