Mailing List Archive

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

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

From: Dong Aisheng <aisheng.dong@freescale.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@linaro.org>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Dong Aisheng <aisheng.dong@freescale.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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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