From c0356db7d1b66840882744cbd9d9c5960b2d88c7 Mon Sep 17 00:00:00 2001 From: Ulf Hansson Date: Tue, 27 Jan 2015 21:13:42 +0100 Subject: [PATCH] PM / Domains: Eliminate the mutex for the generic_pm_domain_data While adding devices to their PM domains, dev_pm_qos_add_notifier() was invoked while allocating the generic_pm_domain_data for the device. Since the generic_pm_domain_data's device pointer will be assigned after allocation, the ->genpd_dev_pm_qos_notifier() callback could be called prior having a valid pointer to the device. Similar scenario existed while removing a device from a genpd. To cope with these scenarios a mutex was used to protect the pointer to the device. By re-order the sequence for when dev_pm_qos_add|remove_notifier() are invoked, we make sure the ->genpd_dev_pm_qos_notifier() callback are always called with a valid device pointer available. In this way, we eliminate the need for protecting the pointer and thus we can remove the mutex from the struct generic_pm_domain_data. Signed-off-by: Ulf Hansson Signed-off-by: Rafael J. Wysocki --- drivers/base/power/domain.c | 37 ++++++++++++++----------------------- include/linux/pm_domain.h | 1 - 2 files changed, 14 insertions(+), 24 deletions(-) diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c index 88198ba919d9..1f026c18bc5c 100644 --- a/drivers/base/power/domain.c +++ b/drivers/base/power/domain.c @@ -344,14 +344,7 @@ static int genpd_dev_pm_qos_notifier(struct notifier_block *nb, struct device *dev; gpd_data = container_of(nb, struct generic_pm_domain_data, nb); - - mutex_lock(&gpd_data->lock); dev = gpd_data->base.dev; - if (!dev) { - mutex_unlock(&gpd_data->lock); - return NOTIFY_DONE; - } - mutex_unlock(&gpd_data->lock); for (;;) { struct generic_pm_domain *genpd; @@ -1392,16 +1385,12 @@ static struct generic_pm_domain_data *genpd_alloc_dev_data(struct device *dev) if (!gpd_data) return NULL; - mutex_init(&gpd_data->lock); - gpd_data->nb.notifier_call = genpd_dev_pm_qos_notifier; - dev_pm_qos_add_notifier(dev, &gpd_data->nb); return gpd_data; } static void genpd_free_dev_data(struct device *dev, struct generic_pm_domain_data *gpd_data) { - dev_pm_qos_remove_notifier(dev, &gpd_data->nb); kfree(gpd_data); } @@ -1414,7 +1403,7 @@ static void genpd_free_dev_data(struct device *dev, int __pm_genpd_add_device(struct generic_pm_domain *genpd, struct device *dev, struct gpd_timing_data *td) { - struct generic_pm_domain_data *gpd_data_new, *gpd_data = NULL; + struct generic_pm_domain_data *gpd_data; int ret = 0; dev_dbg(dev, "%s()\n", __func__); @@ -1422,8 +1411,8 @@ int __pm_genpd_add_device(struct generic_pm_domain *genpd, struct device *dev, if (IS_ERR_OR_NULL(genpd) || IS_ERR_OR_NULL(dev)) return -EINVAL; - gpd_data_new = genpd_alloc_dev_data(dev); - if (!gpd_data_new) + gpd_data = genpd_alloc_dev_data(dev); + if (!gpd_data) return -ENOMEM; genpd_acquire_lock(genpd); @@ -1445,7 +1434,6 @@ int __pm_genpd_add_device(struct generic_pm_domain *genpd, struct device *dev, goto out; } - gpd_data = gpd_data_new; dev->power.subsys_data->domain_data = &gpd_data->base; if (td) @@ -1461,19 +1449,20 @@ int __pm_genpd_add_device(struct generic_pm_domain *genpd, struct device *dev, genpd->device_count++; genpd->max_off_time_changed = true; - mutex_lock(&gpd_data->lock); gpd_data->base.dev = dev; list_add_tail(&gpd_data->base.list_node, &genpd->dev_list); gpd_data->need_restore = -1; gpd_data->td.constraint_changed = true; gpd_data->td.effective_constraint_ns = -1; - mutex_unlock(&gpd_data->lock); + gpd_data->nb.notifier_call = genpd_dev_pm_qos_notifier; out: genpd_release_lock(genpd); - if (gpd_data != gpd_data_new) - genpd_free_dev_data(dev, gpd_data_new); + if (ret) + genpd_free_dev_data(dev, gpd_data); + else + dev_pm_qos_add_notifier(dev, &gpd_data->nb); return ret; } @@ -1509,6 +1498,11 @@ int pm_genpd_remove_device(struct generic_pm_domain *genpd, || pd_to_genpd(dev->pm_domain) != genpd) return -EINVAL; + /* The above validation also means we have existing domain_data. */ + pdd = dev->power.subsys_data->domain_data; + gpd_data = to_gpd_data(pdd); + dev_pm_qos_remove_notifier(dev, &gpd_data->nb); + genpd_acquire_lock(genpd); if (genpd->prepared_count > 0) { @@ -1525,16 +1519,12 @@ int pm_genpd_remove_device(struct generic_pm_domain *genpd, spin_lock_irq(&dev->power.lock); dev->pm_domain = NULL; - pdd = dev->power.subsys_data->domain_data; list_del_init(&pdd->list_node); - gpd_data = to_gpd_data(pdd); dev->power.subsys_data->domain_data = NULL; spin_unlock_irq(&dev->power.lock); - mutex_lock(&gpd_data->lock); pdd->dev = NULL; - mutex_unlock(&gpd_data->lock); genpd_release_lock(genpd); @@ -1545,6 +1535,7 @@ int pm_genpd_remove_device(struct generic_pm_domain *genpd, out: genpd_release_lock(genpd); + dev_pm_qos_add_notifier(dev, &gpd_data->nb); return ret; } diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h index e160a0bba28d..080e778118ba 100644 --- a/include/linux/pm_domain.h +++ b/include/linux/pm_domain.h @@ -113,7 +113,6 @@ struct generic_pm_domain_data { struct pm_domain_data base; struct gpd_timing_data td; struct notifier_block nb; - struct mutex lock; int need_restore; }; -- 2.45.2