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Commit 323c1d0e authored by Rama Aparna Mallavarapu's avatar Rama Aparna Mallavarapu
Browse files

Revert "devfreq: bwmon: Serialize update_devfreq with governor start/stop()" 



The commit 'e42d9b00' causes a deadlock
as it introduces reverse lock ordering between df->lock and mon_lock.
Below is the sequence for the deadlock.

       gov_stop					update_bw_hwmon
mutex_lock(&df->lock)			mutex_lock(&node->mon_lock);
........					........
stop_monitor(df,true)			mutex_lock(&df->lock);
	mutex_lock(&node->mon_lock);		update_devfreq();
        ....
	mutex_unlock(&node->mon_lock);		mutex_unlock(&df->lock);
...						.........
mutex_unlock(&df->lock)			mutex_unlock(&node->mon_lock);

Hence revert this commit to fix the deadlock. This reverts commit
e42d9b00.

Change-Id: I1c4bd52ac462b4f1fdec4b494b6fb74e00fd72f8
Signed-off-by: default avatarRama Aparna Mallavarapu <aparnam@codeaurora.org>
parent b39b9019

drivers/devfreq/governor_bw_hwmon.c

+0 −6
Original line number Original line Diff line number Diff line
@@ -590,11 +590,9 @@ static int gov_start(struct devfreq *df) 
	struct bw_hwmon *hw;

	struct bw_hwmon *hw;

	struct devfreq_dev_status stat;

	struct devfreq_dev_status stat;





	mutex_lock(&df->lock);

	node = find_hwmon_node(df);

	node = find_hwmon_node(df);

	if (!node) {

	if (!node) {

		dev_err(dev, "Unable to find HW monitor!\n");

		dev_err(dev, "Unable to find HW monitor!\n");

		mutex_unlock(&df->lock);

		return -ENODEV;

		return -ENODEV;

	}

	}

	hw = node->hw;

	hw = node->hw;
@@ -619,7 +617,6 @@ static int gov_start(struct devfreq *df) 
	if (ret)

	if (ret)

		goto err_sysfs;

		goto err_sysfs;





	mutex_unlock(&df->lock);

	return 0;

	return 0;





err_sysfs:

err_sysfs:
@@ -629,7 +626,6 @@ static int gov_start(struct devfreq *df) 
	node->orig_data = NULL;

	node->orig_data = NULL;

	hw->df = NULL;

	hw->df = NULL;

	node->dev_ab = NULL;

	node->dev_ab = NULL;

	mutex_unlock(&df->lock);

	return ret;

	return ret;

}

}
@@ -638,7 +634,6 @@ static void gov_stop(struct devfreq *df) 
	struct hwmon_node *node = df->data;

	struct hwmon_node *node = df->data;

	struct bw_hwmon *hw = node->hw;

	struct bw_hwmon *hw = node->hw;





	mutex_lock(&df->lock);

	sysfs_remove_group(&df->dev.kobj, node->attr_grp);

	sysfs_remove_group(&df->dev.kobj, node->attr_grp);

	stop_monitor(df, true);

	stop_monitor(df, true);

	df->data = node->orig_data;

	df->data = node->orig_data;
@@ -653,7 +648,6 @@ static void gov_stop(struct devfreq *df) 
	if (node->dev_ab)

	if (node->dev_ab)

		*node->dev_ab = 0;

		*node->dev_ab = 0;

	node->dev_ab = NULL;

	node->dev_ab = NULL;

	mutex_unlock(&df->lock);

}

}





static int gov_suspend(struct devfreq *df)

static int gov_suspend(struct devfreq *df)