From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755378AbaHUNsN (ORCPT ); Thu, 21 Aug 2014 09:48:13 -0400 Received: from devils.ext.ti.com ([198.47.26.153]:56258 "EHLO devils.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754996AbaHUNsJ (ORCPT ); Thu, 21 Aug 2014 09:48:09 -0400 From: Tero Kristo To: , , , , CC: Subject: [PATCH] clk: prevent erronous parsing of children during rate change Date: Thu, 21 Aug 2014 16:47:45 +0300 Message-ID: <1408628866-32351-1-git-send-email-t-kristo@ti.com> X-Mailer: git-send-email 1.7.9.5 MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Signed-off-by: Tero Kristo To: Mike Turquette Reported-by: Nishanth Menon --- drivers/clk/clk.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index b76fa69..bacc06f 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -1467,6 +1467,7 @@ 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; @@ -1502,7 +1503,11 @@ 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; -- 1.7.9.5 From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tero Kristo Subject: [PATCH] clk: prevent erronous parsing of children during rate change Date: Thu, 21 Aug 2014 16:47:45 +0300 Message-ID: <1408628866-32351-1-git-send-email-t-kristo@ti.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: Sender: linux-kernel-owner@vger.kernel.org To: linux-kernel@vger.kernel.org, linux-omap@vger.kernel.org, tony@atomide.com, nm@ti.com, mturquette@linaro.org Cc: linux-arm-kernel@lists.infradead.org List-Id: linux-omap@vger.kernel.org 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. Signed-off-by: Tero Kristo To: Mike Turquette Reported-by: Nishanth Menon --- drivers/clk/clk.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index b76fa69..bacc06f 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -1467,6 +1467,7 @@ 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; @@ -1502,7 +1503,11 @@ 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; -- 1.7.9.5 From mboxrd@z Thu Jan 1 00:00:00 1970 From: t-kristo@ti.com (Tero Kristo) Date: Thu, 21 Aug 2014 16:47:45 +0300 Subject: [PATCH] clk: prevent erronous parsing of children during rate change Message-ID: <1408628866-32351-1-git-send-email-t-kristo@ti.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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. Signed-off-by: Tero Kristo To: Mike Turquette Reported-by: Nishanth Menon --- drivers/clk/clk.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index b76fa69..bacc06f 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -1467,6 +1467,7 @@ 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; @@ -1502,7 +1503,11 @@ 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; -- 1.7.9.5