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authorTero Kristo <t-kristo@ti.com>2014-08-21 16:47:45 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-10-05 13:41:12 -0700
commite8c736166ec62bf3143b5f59ee9326e11009dd55 (patch)
tree15c284b1b866ef1a50035ab1f382adcb7bcf7c3f
parent5e2c757758986247bf709825201931975dcdf748 (diff)
downloadlwn-e8c736166ec62bf3143b5f59ee9326e11009dd55.tar.gz
lwn-e8c736166ec62bf3143b5f59ee9326e11009dd55.zip
clk: prevent erronous parsing of children during rate change
commit 067bb1741c27c8d3b74ac98c0b8fc12b31e67005 upstream. In some cases, clocks can switch their parent with clk_set_rate, for example clk_mux can do this in some cases. Current implementation of clk_change_rate uses un-safe list iteration on the clock children, which will cause wrong clocks to be parsed in case any of the clock children change their parents during the change rate operation. Fixed by using the safe list iterator instead. The problem was detected due to some divide by zero errors generated by clock init on dra7-evm board, see discussion under http://article.gmane.org/gmane.linux.ports.arm.kernel/349180 for details. Fixes: 71472c0c06cf ("clk: add support for clock reparent on set_rate") Signed-off-by: Tero Kristo <t-kristo@ti.com> Reported-by: Nishanth Menon <nm@ti.com> Signed-off-by: Mike Turquette <mturquette@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/clk/clk.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 8b73edef151d..4cc83ef7ef61 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1495,6 +1495,7 @@ static struct clk *clk_propagate_rate_change(struct clk *clk, unsigned long even
static void clk_change_rate(struct clk *clk)
{
struct clk *child;
+ struct hlist_node *tmp;
unsigned long old_rate;
unsigned long best_parent_rate = 0;
bool skip_set_rate = false;
@@ -1530,7 +1531,11 @@ static void clk_change_rate(struct clk *clk)
if (clk->notifier_count && old_rate != clk->rate)
__clk_notify(clk, POST_RATE_CHANGE, old_rate, clk->rate);
- hlist_for_each_entry(child, &clk->children, child_node) {
+ /*
+ * Use safe iteration, as change_rate can actually swap parents
+ * for certain clock types.
+ */
+ hlist_for_each_entry_safe(child, tmp, &clk->children, child_node) {
/* Skip children who will be reparented to another clock */
if (child->new_parent && child->new_parent != clk)
continue;