linux-kernel - [PATCH 4.19 004/220] Revert "OPP: Protect dev_list with opp

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Message-Id: <20191122100912.995214228@linuxfoundation.org>
Date:   Fri, 22 Nov 2019 11:26:09 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Viresh Kumar <viresh.kumar@...aro.org>,
        "kernelci.org bot" <bot@...nelci.org>,
        Niklas Cassel <niklas.cassel@...aro.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 004/220] Revert "OPP: Protect dev_list with opp_table lock"

From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

This reverts commit 4c64ce947cfa447993efe005cbaad7ba31a91612 which is
commit 3d2556992a878a2210d3be498416aee39e0c32aa upstream.

Turns out to break the build on the odroid machines, so it needs to be
reverted.

Reported-by: Viresh Kumar <viresh.kumar@...aro.org>
Reported-by: "kernelci.org bot" <bot@...nelci.org>
Cc: Niklas Cassel <niklas.cassel@...aro.org>
Cc: Sasha Levin <sashal@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/opp/core.c |   21 ++-------------------
 drivers/opp/cpu.c  |    2 --
 drivers/opp/opp.h  |    2 +-
 3 files changed, 3 insertions(+), 22 deletions(-)

--- a/drivers/opp/core.c
+++ b/drivers/opp/core.c
@@ -48,14 +48,9 @@ static struct opp_device *_find_opp_dev(
 static struct opp_table *_find_opp_table_unlocked(struct device *dev)
 {
 	struct opp_table *opp_table;
-	bool found;
 
 	list_for_each_entry(opp_table, &opp_tables, node) {
-		mutex_lock(&opp_table->lock);
-		found = !!_find_opp_dev(dev, opp_table);
-		mutex_unlock(&opp_table->lock);
-
-		if (found) {
+		if (_find_opp_dev(dev, opp_table)) {
 			_get_opp_table_kref(opp_table);
 
 			return opp_table;
@@ -771,8 +766,6 @@ struct opp_device *_add_opp_dev(const st
 
 	/* Initialize opp-dev */
 	opp_dev->dev = dev;
-
-	mutex_lock(&opp_table->lock);
 	list_add(&opp_dev->node, &opp_table->dev_list);
 
 	/* Create debugfs entries for the opp_table */
@@ -780,7 +773,6 @@ struct opp_device *_add_opp_dev(const st
 	if (ret)
 		dev_err(dev, "%s: Failed to register opp debugfs (%d)\n",
 			__func__, ret);
-	mutex_unlock(&opp_table->lock);
 
 	return opp_dev;
 }
@@ -799,7 +791,6 @@ static struct opp_table *_allocate_opp_t
 	if (!opp_table)
 		return NULL;
 
-	mutex_init(&opp_table->lock);
 	INIT_LIST_HEAD(&opp_table->dev_list);
 
 	opp_dev = _add_opp_dev(dev, opp_table);
@@ -821,6 +812,7 @@ static struct opp_table *_allocate_opp_t
 
 	BLOCKING_INIT_NOTIFIER_HEAD(&opp_table->head);
 	INIT_LIST_HEAD(&opp_table->opp_list);
+	mutex_init(&opp_table->lock);
 	kref_init(&opp_table->kref);
 
 	/* Secure the device table modification */
@@ -862,10 +854,6 @@ static void _opp_table_kref_release(stru
 	if (!IS_ERR(opp_table->clk))
 		clk_put(opp_table->clk);
 
-	/*
-	 * No need to take opp_table->lock here as we are guaranteed that no
-	 * references to the OPP table are taken at this point.
-	 */
 	opp_dev = list_first_entry(&opp_table->dev_list, struct opp_device,
 				   node);
 
@@ -1731,9 +1719,6 @@ void _dev_pm_opp_remove_table(struct opp
 {
 	struct dev_pm_opp *opp, *tmp;
 
-	/* Protect dev_list */
-	mutex_lock(&opp_table->lock);
-
 	/* Find if opp_table manages a single device */
 	if (list_is_singular(&opp_table->dev_list)) {
 		/* Free static OPPs */
@@ -1751,8 +1736,6 @@ void _dev_pm_opp_remove_table(struct opp
 	} else {
 		_remove_opp_dev(_find_opp_dev(dev, opp_table), opp_table);
 	}
-
-	mutex_unlock(&opp_table->lock);
 }
 
 void _dev_pm_opp_find_and_remove_table(struct device *dev, bool remove_all)
--- a/drivers/opp/cpu.c
+++ b/drivers/opp/cpu.c
@@ -222,10 +222,8 @@ int dev_pm_opp_get_sharing_cpus(struct d
 	cpumask_clear(cpumask);
 
 	if (opp_table->shared_opp == OPP_TABLE_ACCESS_SHARED) {
-		mutex_lock(&opp_table->lock);
 		list_for_each_entry(opp_dev, &opp_table->dev_list, node)
 			cpumask_set_cpu(opp_dev->dev->id, cpumask);
-		mutex_unlock(&opp_table->lock);
 	} else {
 		cpumask_set_cpu(cpu_dev->id, cpumask);
 	}
--- a/drivers/opp/opp.h
+++ b/drivers/opp/opp.h
@@ -126,7 +126,7 @@ enum opp_table_access {
  * @dev_list:	list of devices that share these OPPs
  * @opp_list:	table of opps
  * @kref:	for reference count of the table.
- * @lock:	mutex protecting the opp_list and dev_list.
+ * @lock:	mutex protecting the opp_list.
  * @np:		struct device_node pointer for opp's DT node.
  * @clock_latency_ns_max: Max clock latency in nanoseconds.
  * @shared_opp: OPP is shared between multiple devices.