Re: [PATCH v2] genpd: Fix up terminology with parent/child

Kieran Bingham
2020-07-09T08:48:46Z

Hi Kees,

On 09/07/2020 00:32, Kees Cook wrote:
> The genpd infrastructure uses the terms master/slave, but such uses have
> no external exposures (not even in Documentation/driver-api/pm/*) and are
> not mandated by nor associated with any external specifications. Change
> the language used through-out to parent/child.
>
> There was one possible exception in the debugfs node
> "pm_genpd/pm_genpd_summary" but its path has no hits outside of the
> kernel itself when performing a code search[1], and it seems even this
> single usage has been non-functional since it was introduced due to a
> typo in the Python ("apend" instead of correct "append"). Fix the typo
> while we're at it.

Good spot

>
> [1] https://codesearch.debian.net/
>
> Signed-off-by: Kees Cook <keescook@chromium.org>

Parent/child works much better here I think. I wonder if that should be
suggested as an alternatvie on the coding-style patch too ...

> ---
> v2: leader/follower -> parent/child (ulf, rafael)
> v1: https://lore.kernel.org/lkml/202007080131.3E6D0858@keescook
> This is motivated by the recent discussions over coding style:
> https://lore.kernel.org/lkml/159419296487.2464622.863943877093636532.stgit@dwillia2-desk3.amr.corp.intel.com/
> ---
> drivers/base/power/domain.c | 194 +++++++++++++--------------
> drivers/base/power/domain_governor.c | 12 +-
> include/linux/pm_domain.h | 12 +-
> scripts/gdb/linux/genpd.py | 12 +-

for scripts/gdb/linux/genpd.py:

Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

> 4 files changed, 115 insertions(+), 115 deletions(-)
>
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index 0a01df608849..2cb5e04cf86c 100644
> --- a/drivers/base/power/domain.c
> +++ b/drivers/base/power/domain.c
> @@ -263,18 +263,18 @@ static int _genpd_reeval_performance_state(struct generic_pm_domain *genpd,
> /*
> * Traverse all sub-domains within the domain. This can be
> * done without any additional locking as the link->performance_state
> - * field is protected by the master genpd->lock, which is already taken.
> + * field is protected by the parent genpd->lock, which is already taken.
> *
> * Also note that link->performance_state (subdomain's performance state
> - * requirement to master domain) is different from
> - * link->slave->performance_state (current performance state requirement
> + * requirement to parent domain) is different from
> + * link->child->performance_state (current performance state requirement
> * of the devices/sub-domains of the subdomain) and so can have a
> * different value.
> *
> * Note that we also take vote from powered-off sub-domains into account
> * as the same is done for devices right now.
> */
> - list_for_each_entry(link, &genpd->master_links, master_node) {
> + list_for_each_entry(link, &genpd->parent_links, parent_node) {
> if (link->performance_state > state)
> state = link->performance_state;
> }
> @@ -285,40 +285,40 @@ static int _genpd_reeval_performance_state(struct generic_pm_domain *genpd,
> static int _genpd_set_performance_state(struct generic_pm_domain *genpd,
> unsigned int state, int depth)
> {
> - struct generic_pm_domain *master;
> + struct generic_pm_domain *parent;
> struct gpd_link *link;
> - int master_state, ret;
> + int parent_state, ret;
>
> if (state == genpd->performance_state)
> return 0;
>
> - /* Propagate to masters of genpd */
> - list_for_each_entry(link, &genpd->slave_links, slave_node) {
> - master = link->master;
> + /* Propagate to parents of genpd */
> + list_for_each_entry(link, &genpd->child_links, child_node) {
> + parent = link->parent;
>
> - if (!master->set_performance_state)
> + if (!parent->set_performance_state)
> continue;
>
> - /* Find master's performance state */
> + /* Find parent's performance state */
> ret = dev_pm_opp_xlate_performance_state(genpd->opp_table,
> - master->opp_table,
> + parent->opp_table,
> state);
> if (unlikely(ret < 0))
> goto err;
>
> - master_state = ret;
> + parent_state = ret;
>
> - genpd_lock_nested(master, depth + 1);
> + genpd_lock_nested(parent, depth + 1);
>
> link->prev_performance_state = link->performance_state;
> - link->performance_state = master_state;
> - master_state = _genpd_reeval_performance_state(master,
> - master_state);
> - ret = _genpd_set_performance_state(master, master_state, depth + 1);
> + link->performance_state = parent_state;
> + parent_state = _genpd_reeval_performance_state(parent,
> + parent_state);
> + ret = _genpd_set_performance_state(parent, parent_state, depth + 1);
> if (ret)
> link->performance_state = link->prev_performance_state;
>
> - genpd_unlock(master);
> + genpd_unlock(parent);
>
> if (ret)
> goto err;
> @@ -333,26 +333,26 @@ static int _genpd_set_performance_state(struct generic_pm_domain *genpd,
>
> err:
> /* Encountered an error, lets rollback */
> - list_for_each_entry_continue_reverse(link, &genpd->slave_links,
> - slave_node) {
> - master = link->master;
> + list_for_each_entry_continue_reverse(link, &genpd->child_links,
> + child_node) {
> + parent = link->parent;
>
> - if (!master->set_performance_state)
> + if (!parent->set_performance_state)
> continue;
>
> - genpd_lock_nested(master, depth + 1);
> + genpd_lock_nested(parent, depth + 1);
>
> - master_state = link->prev_performance_state;
> - link->performance_state = master_state;
> + parent_state = link->prev_performance_state;
> + link->performance_state = parent_state;
>
> - master_state = _genpd_reeval_performance_state(master,
> - master_state);
> - if (_genpd_set_performance_state(master, master_state, depth + 1)) {
> + parent_state = _genpd_reeval_performance_state(parent,
> + parent_state);
> + if (_genpd_set_performance_state(parent, parent_state, depth + 1)) {
> pr_err("%s: Failed to roll back to %d performance state\n",
> - master->name, master_state);
> + parent->name, parent_state);
> }
>
> - genpd_unlock(master);
> + genpd_unlock(parent);
> }
>
> return ret;
> @@ -552,7 +552,7 @@ static int genpd_power_off(struct generic_pm_domain *genpd, bool one_dev_on,
>
> /*
> * If sd_count > 0 at this point, one of the subdomains hasn't
> - * managed to call genpd_power_on() for the master yet after
> + * managed to call genpd_power_on() for the parent yet after
> * incrementing it. In that case genpd_power_on() will wait
> * for us to drop the lock, so we can call .power_off() and let
> * the genpd_power_on() restore power for us (this shouldn't
> @@ -566,22 +566,22 @@ static int genpd_power_off(struct generic_pm_domain *genpd, bool one_dev_on,
> genpd->status = GPD_STATE_POWER_OFF;
> genpd_update_accounting(genpd);
>
> - list_for_each_entry(link, &genpd->slave_links, slave_node) {
> - genpd_sd_counter_dec(link->master);
> - genpd_lock_nested(link->master, depth + 1);
> - genpd_power_off(link->master, false, depth + 1);
> - genpd_unlock(link->master);
> + list_for_each_entry(link, &genpd->child_links, child_node) {
> + genpd_sd_counter_dec(link->parent);
> + genpd_lock_nested(link->parent, depth + 1);
> + genpd_power_off(link->parent, false, depth + 1);
> + genpd_unlock(link->parent);
> }
>
> return 0;
> }
>
> /**
> - * genpd_power_on - Restore power to a given PM domain and its masters.
> + * genpd_power_on - Restore power to a given PM domain and its parents.
> * @genpd: PM domain to power up.
> * @depth: nesting count for lockdep.
> *
> - * Restore power to @genpd and all of its masters so that it is possible to
> + * Restore power to @genpd and all of its parents so that it is possible to
> * resume a device belonging to it.
> */
> static int genpd_power_on(struct generic_pm_domain *genpd, unsigned int depth)
> @@ -594,20 +594,20 @@ static int genpd_power_on(struct generic_pm_domain *genpd, unsigned int depth)
>
> /*
> * The list is guaranteed not to change while the loop below is being
> - * executed, unless one of the masters' .power_on() callbacks fiddles
> + * executed, unless one of the parents' .power_on() callbacks fiddles
> * with it.
> */
> - list_for_each_entry(link, &genpd->slave_links, slave_node) {
> - struct generic_pm_domain *master = link->master;
> + list_for_each_entry(link, &genpd->child_links, child_node) {
> + struct generic_pm_domain *parent = link->parent;
>
> - genpd_sd_counter_inc(master);
> + genpd_sd_counter_inc(parent);
>
> - genpd_lock_nested(master, depth + 1);
> - ret = genpd_power_on(master, depth + 1);
> - genpd_unlock(master);
> + genpd_lock_nested(parent, depth + 1);
> + ret = genpd_power_on(parent, depth + 1);
> + genpd_unlock(parent);
>
> if (ret) {
> - genpd_sd_counter_dec(master);
> + genpd_sd_counter_dec(parent);
> goto err;
> }
> }
> @@ -623,12 +623,12 @@ static int genpd_power_on(struct generic_pm_domain *genpd, unsigned int depth)
>
> err:
> list_for_each_entry_continue_reverse(link,
> - &genpd->slave_links,
> - slave_node) {
> - genpd_sd_counter_dec(link->master);
> - genpd_lock_nested(link->master, depth + 1);
> - genpd_power_off(link->master, false, depth + 1);
> - genpd_unlock(link->master);
> + &genpd->child_links,
> + child_node) {
> + genpd_sd_counter_dec(link->parent);
> + genpd_lock_nested(link->parent, depth + 1);
> + genpd_power_off(link->parent, false, depth + 1);
> + genpd_unlock(link->parent);
> }
>
> return ret;
> @@ -932,13 +932,13 @@ late_initcall(genpd_power_off_unused);
> #ifdef CONFIG_PM_SLEEP
>
> /**
> - * genpd_sync_power_off - Synchronously power off a PM domain and its masters.
> + * genpd_sync_power_off - Synchronously power off a PM domain and its parents.
> * @genpd: PM domain to power off, if possible.
> * @use_lock: use the lock.
> * @depth: nesting count for lockdep.
> *
> * Check if the given PM domain can be powered off (during system suspend or
> - * hibernation) and do that if so. Also, in that case propagate to its masters.
> + * hibernation) and do that if so. Also, in that case propagate to its parents.
> *
> * This function is only called in "noirq" and "syscore" stages of system power
> * transitions. The "noirq" callbacks may be executed asynchronously, thus in
> @@ -963,21 +963,21 @@ static void genpd_sync_power_off(struct generic_pm_domain *genpd, bool use_lock,
>
> genpd->status = GPD_STATE_POWER_OFF;
>
> - list_for_each_entry(link, &genpd->slave_links, slave_node) {
> - genpd_sd_counter_dec(link->master);
> + list_for_each_entry(link, &genpd->child_links, child_node) {
> + genpd_sd_counter_dec(link->parent);
>
> if (use_lock)
> - genpd_lock_nested(link->master, depth + 1);
> + genpd_lock_nested(link->parent, depth + 1);
>
> - genpd_sync_power_off(link->master, use_lock, depth + 1);
> + genpd_sync_power_off(link->parent, use_lock, depth + 1);
>
> if (use_lock)
> - genpd_unlock(link->master);
> + genpd_unlock(link->parent);
> }
> }
>
> /**
> - * genpd_sync_power_on - Synchronously power on a PM domain and its masters.
> + * genpd_sync_power_on - Synchronously power on a PM domain and its parents.
> * @genpd: PM domain to power on.
> * @use_lock: use the lock.
> * @depth: nesting count for lockdep.
> @@ -994,16 +994,16 @@ static void genpd_sync_power_on(struct generic_pm_domain *genpd, bool use_lock,
> if (genpd_status_on(genpd))
> return;
>
> - list_for_each_entry(link, &genpd->slave_links, slave_node) {
> - genpd_sd_counter_inc(link->master);
> + list_for_each_entry(link, &genpd->child_links, child_node) {
> + genpd_sd_counter_inc(link->parent);
>
> if (use_lock)
> - genpd_lock_nested(link->master, depth + 1);
> + genpd_lock_nested(link->parent, depth + 1);
>
> - genpd_sync_power_on(link->master, use_lock, depth + 1);
> + genpd_sync_power_on(link->parent, use_lock, depth + 1);
>
> if (use_lock)
> - genpd_unlock(link->master);
> + genpd_unlock(link->parent);
> }
>
> _genpd_power_on(genpd, false);
> @@ -1443,12 +1443,12 @@ static void genpd_update_cpumask(struct generic_pm_domain *genpd,
> if (!genpd_is_cpu_domain(genpd))
> return;
>
> - list_for_each_entry(link, &genpd->slave_links, slave_node) {
> - struct generic_pm_domain *master = link->master;
> + list_for_each_entry(link, &genpd->child_links, child_node) {
> + struct generic_pm_domain *parent = link->parent;
>
> - genpd_lock_nested(master, depth + 1);
> - genpd_update_cpumask(master, cpu, set, depth + 1);
> - genpd_unlock(master);
> + genpd_lock_nested(parent, depth + 1);
> + genpd_update_cpumask(parent, cpu, set, depth + 1);
> + genpd_unlock(parent);
> }
>
> if (set)
> @@ -1636,17 +1636,17 @@ static int genpd_add_subdomain(struct generic_pm_domain *genpd,
> goto out;
> }
>
> - list_for_each_entry(itr, &genpd->master_links, master_node) {
> - if (itr->slave == subdomain && itr->master == genpd) {
> + list_for_each_entry(itr, &genpd->parent_links, parent_node) {
> + if (itr->child == subdomain && itr->parent == genpd) {
> ret = -EINVAL;
> goto out;
> }
> }
>
> - link->master = genpd;
> - list_add_tail(&link->master_node, &genpd->master_links);
> - link->slave = subdomain;
> - list_add_tail(&link->slave_node, &subdomain->slave_links);
> + link->parent = genpd;
> + list_add_tail(&link->parent_node, &genpd->parent_links);
> + link->child = subdomain;
> + list_add_tail(&link->child_node, &subdomain->child_links);
> if (genpd_status_on(subdomain))
> genpd_sd_counter_inc(genpd);
>
> @@ -1660,7 +1660,7 @@ static int genpd_add_subdomain(struct generic_pm_domain *genpd,
>
> /**
> * pm_genpd_add_subdomain - Add a subdomain to an I/O PM domain.
> - * @genpd: Master PM domain to add the subdomain to.
> + * @genpd: Leader PM domain to add the subdomain to.
> * @subdomain: Subdomain to be added.
> */
> int pm_genpd_add_subdomain(struct generic_pm_domain *genpd,
> @@ -1678,7 +1678,7 @@ EXPORT_SYMBOL_GPL(pm_genpd_add_subdomain);
>
> /**
> * pm_genpd_remove_subdomain - Remove a subdomain from an I/O PM domain.
> - * @genpd: Master PM domain to remove the subdomain from.
> + * @genpd: Leader PM domain to remove the subdomain from.
> * @subdomain: Subdomain to be removed.
> */
> int pm_genpd_remove_subdomain(struct generic_pm_domain *genpd,
> @@ -1693,19 +1693,19 @@ int pm_genpd_remove_subdomain(struct generic_pm_domain *genpd,
> genpd_lock(subdomain);
> genpd_lock_nested(genpd, SINGLE_DEPTH_NESTING);
>
> - if (!list_empty(&subdomain->master_links) || subdomain->device_count) {
> + if (!list_empty(&subdomain->parent_links) || subdomain->device_count) {
> pr_warn("%s: unable to remove subdomain %s\n",
> genpd->name, subdomain->name);
> ret = -EBUSY;
> goto out;
> }
>
> - list_for_each_entry_safe(link, l, &genpd->master_links, master_node) {
> - if (link->slave != subdomain)
> + list_for_each_entry_safe(link, l, &genpd->parent_links, parent_node) {
> + if (link->child != subdomain)
> continue;
>
> - list_del(&link->master_node);
> - list_del(&link->slave_node);
> + list_del(&link->parent_node);
> + list_del(&link->child_node);
> kfree(link);
> if (genpd_status_on(subdomain))
> genpd_sd_counter_dec(genpd);
> @@ -1770,8 +1770,8 @@ int pm_genpd_init(struct generic_pm_domain *genpd,
> if (IS_ERR_OR_NULL(genpd))
> return -EINVAL;
>
> - INIT_LIST_HEAD(&genpd->master_links);
> - INIT_LIST_HEAD(&genpd->slave_links);
> + INIT_LIST_HEAD(&genpd->parent_links);
> + INIT_LIST_HEAD(&genpd->child_links);
> INIT_LIST_HEAD(&genpd->dev_list);
> genpd_lock_init(genpd);
> genpd->gov = gov;
> @@ -1848,15 +1848,15 @@ static int genpd_remove(struct generic_pm_domain *genpd)
> return -EBUSY;
> }
>
> - if (!list_empty(&genpd->master_links) || genpd->device_count) {
> + if (!list_empty(&genpd->parent_links) || genpd->device_count) {
> genpd_unlock(genpd);
> pr_err("%s: unable to remove %s\n", __func__, genpd->name);
> return -EBUSY;
> }
>
> - list_for_each_entry_safe(link, l, &genpd->slave_links, slave_node) {
> - list_del(&link->master_node);
> - list_del(&link->slave_node);
> + list_for_each_entry_safe(link, l, &genpd->child_links, child_node) {
> + list_del(&link->parent_node);
> + list_del(&link->child_node);
> kfree(link);
> }
>
> @@ -2827,12 +2827,12 @@ static int genpd_summary_one(struct seq_file *s,
>
> /*
> * Modifications on the list require holding locks on both
> - * master and slave, so we are safe.
> + * parent and child, so we are safe.
> * Also genpd->name is immutable.
> */
> - list_for_each_entry(link, &genpd->master_links, master_node) {
> - seq_printf(s, "%s", link->slave->name);
> - if (!list_is_last(&link->master_node, &genpd->master_links))
> + list_for_each_entry(link, &genpd->parent_links, parent_node) {
> + seq_printf(s, "%s", link->child->name);
> + if (!list_is_last(&link->parent_node, &genpd->parent_links))
> seq_puts(s, ", ");
> }
>
> @@ -2860,7 +2860,7 @@ static int summary_show(struct seq_file *s, void *data)
> struct generic_pm_domain *genpd;
> int ret = 0;
>
> - seq_puts(s, "domain status slaves\n");
> + seq_puts(s, "domain status children\n");
> seq_puts(s, " /device runtime status\n");
> seq_puts(s, "----------------------------------------------------------------------\n");
>
> @@ -2915,8 +2915,8 @@ static int sub_domains_show(struct seq_file *s, void *data)
> if (ret)
> return -ERESTARTSYS;
>
> - list_for_each_entry(link, &genpd->master_links, master_node)
> - seq_printf(s, "%s\n", link->slave->name);
> + list_for_each_entry(link, &genpd->parent_links, parent_node)
> + seq_printf(s, "%s\n", link->child->name);
>
> genpd_unlock(genpd);
> return ret;
> diff --git a/drivers/base/power/domain_governor.c b/drivers/base/power/domain_governor.c
> index daa8c7689f7e..490ed7deb99a 100644
> --- a/drivers/base/power/domain_governor.c
> +++ b/drivers/base/power/domain_governor.c
> @@ -135,8 +135,8 @@ static bool __default_power_down_ok(struct dev_pm_domain *pd,
> *
> * All subdomains have been powered off already at this point.
> */
> - list_for_each_entry(link, &genpd->master_links, master_node) {
> - struct generic_pm_domain *sd = link->slave;
> + list_for_each_entry(link, &genpd->parent_links, parent_node) {
> + struct generic_pm_domain *sd = link->child;
> s64 sd_max_off_ns = sd->max_off_time_ns;
>
> if (sd_max_off_ns < 0)
> @@ -217,13 +217,13 @@ static bool default_power_down_ok(struct dev_pm_domain *pd)
> }
>
> /*
> - * We have to invalidate the cached results for the masters, so
> + * We have to invalidate the cached results for the parents, so
> * use the observation that default_power_down_ok() is not
> - * going to be called for any master until this instance
> + * going to be called for any parent until this instance
> * returns.
> */
> - list_for_each_entry(link, &genpd->slave_links, slave_node)
> - link->master->max_off_time_changed = true;
> + list_for_each_entry(link, &genpd->child_links, child_node)
> + link->parent->max_off_time_changed = true;
>
> genpd->max_off_time_ns = -1;
> genpd->max_off_time_changed = false;
> diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
> index 9ec78ee53652..574a1fadb1e5 100644
> --- a/include/linux/pm_domain.h
> +++ b/include/linux/pm_domain.h
> @@ -95,8 +95,8 @@ struct generic_pm_domain {
> struct device dev;
> struct dev_pm_domain domain; /* PM domain operations */
> struct list_head gpd_list_node; /* Node in the global PM domains list */
> - struct list_head master_links; /* Links with PM domain as a master */
> - struct list_head slave_links; /* Links with PM domain as a slave */
> + struct list_head parent_links; /* Links with PM domain as a parent */
> + struct list_head child_links;/* Links with PM domain as a child */
> struct list_head dev_list; /* List of devices */
> struct dev_power_governor *gov;
> struct work_struct power_off_work;
> @@ -151,10 +151,10 @@ static inline struct generic_pm_domain *pd_to_genpd(struct dev_pm_domain *pd)
> }
>
> struct gpd_link {
> - struct generic_pm_domain *master;
> - struct list_head master_node;
> - struct generic_pm_domain *slave;
> - struct list_head slave_node;
> + struct generic_pm_domain *parent;
> + struct list_head parent_node;
> + struct generic_pm_domain *child;
> + struct list_head child_node;
>
> /* Sub-domain's per-master domain performance state */
> unsigned int performance_state;
> diff --git a/scripts/gdb/linux/genpd.py b/scripts/gdb/linux/genpd.py
> index 6ca93bd2949e..39cd1abd8559 100644
> --- a/scripts/gdb/linux/genpd.py
> +++ b/scripts/gdb/linux/genpd.py
> @@ -49,17 +49,17 @@ Output is similar to /sys/kernel/debug/pm_genpd/pm_genpd_summary'''
> else:
> status_string = 'off-{}'.format(genpd['state_idx'])
>
> - slave_names = []
> + child_names = []
> for link in list_for_each_entry(
> - genpd['master_links'],
> + genpd['parent_links'],
> device_link_type.get_type().pointer(),
> - 'master_node'):
> - slave_names.apend(link['slave']['name'])
> + 'parent_node'):
> + child_names.append(link['child']['name'])
>
> gdb.write('%-30s %-15s %s\n' % (
> genpd['name'].string(),
> status_string,
> - ', '.join(slave_names)))
> + ', '.join(child_names)))
>
> # Print devices in domain
> for pm_data in list_for_each_entry(genpd['dev_list'],
> @@ -70,7 +70,7 @@ Output is similar to /sys/kernel/debug/pm_genpd/pm_genpd_summary'''
> gdb.write(' %-50s %s\n' % (kobj_path, rtpm_status_str(dev)))
>
> def invoke(self, arg, from_tty):
> - gdb.write('domain status slaves\n');
> + gdb.write('domain status children\n');
> gdb.write(' /device runtime status\n');
> gdb.write('----------------------------------------------------------------------\n');
> for genpd in list_for_each_entry(
>