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driver core: Fix PM-runtime for links added during consumer probe

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Commit 4c06c4e6cf ("driver core: Fix possible supplier PM-usage
counter imbalance") introduced a regression that causes suppliers
to be suspended prematurely for device links added during consumer
driver probe if the initial PM-runtime status of the consumer is
"suspended" and the consumer is resumed after adding the link and
before pm_runtime_put_suppliers() is called.  In that case,
pm_runtime_put_suppliers() will drop the rpm_active refcount for
the link by one and (since rpm_active is equal to two after the
preceding consumer resume) the supplier's PM-runtime usage counter
will be decremented, which may cause the supplier to suspend even
though the consumer's PM-runtime status is "active".

For this reason, partially revert commit 4c06c4e6cf as the problem
it tried to fix needs to be addressed somewhat differently, and
change pm_runtime_get_suppliers() and pm_runtime_put_suppliers() so
that the latter only drops rpm_active references acquired by the
former.  [This requires adding a new field to struct device_link,
but I coulnd't find a cleaner way to address the issue that would
work in all cases.]

This causes pm_runtime_put_suppliers() to effectively ignore device
links added during consumer probe, so device_link_add() doesn't need
to worry about ensuring that suppliers will remain active after
pm_runtime_put_suppliers() for links created with DL_FLAG_RPM_ACTIVE
set and it only needs to bump up rpm_active by one for those links,
so pm_runtime_active_link() is not necessary any more.

Fixes: 4c06c4e6cf ("driver core: Fix possible supplier PM-usage counter imbalance")
Reported-by: Jon Hunter <jonathanh@nvidia.com>
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Tested-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Rafael J. Wysocki 2019-02-19 17:53:26 +01:00 committed by Greg Kroah-Hartman
parent e4246b0550
commit 36003d4cf5
4 changed files with 9 additions and 29 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

4
drivers/base/core.c
View file

@ -277,7 +277,7 @@ struct device_link *device_link_add(struct device *consumer,
link->flags |= DL_FLAG_PM_RUNTIME;
}
if (flags & DL_FLAG_RPM_ACTIVE)
pm_runtime_active_link(link, supplier);
refcount_inc(&link->rpm_active);
}
if (flags & DL_FLAG_STATELESS) {
@ -310,7 +310,7 @@ struct device_link *device_link_add(struct device *consumer,
if (flags & DL_FLAG_PM_RUNTIME) {
if (flags & DL_FLAG_RPM_ACTIVE)
pm_runtime_active_link(link, supplier);
refcount_inc(&link->rpm_active);
pm_runtime_new_link(consumer);
}

27
drivers/base/power/runtime.c
View file

@ -1626,6 +1626,7 @@ void pm_runtime_get_suppliers(struct device *dev)
list_for_each_entry_rcu(link, &dev->links.suppliers, c_node)
if (link->flags & DL_FLAG_PM_RUNTIME) {
link->supplier_preactivated = true;
refcount_inc(&link->rpm_active);
pm_runtime_get_sync(link->supplier);
}
@ -1645,9 +1646,11 @@ void pm_runtime_put_suppliers(struct device *dev)
idx = device_links_read_lock();
list_for_each_entry_rcu(link, &dev->links.suppliers, c_node)
if (link->flags & DL_FLAG_PM_RUNTIME &&
refcount_dec_not_one(&link->rpm_active))
if (link->supplier_preactivated) {
link->supplier_preactivated = false;
if (refcount_dec_not_one(&link->rpm_active))
pm_runtime_put(link->supplier);
}
device_links_read_unlock(idx);
}
@ -1659,26 +1662,6 @@ void pm_runtime_new_link(struct device *dev)
spin_unlock_irq(&dev->power.lock);
}
/**
* pm_runtime_active_link - Set up new device link as active for PM-runtime.
* @link: Device link to be set up as active.
* @supplier: Supplier end of the link.
*
* Add 2 to the rpm_active refcount of @link and increment the PM-runtime
* usage counter of @supplier once more in case the link is being added while
* the consumer driver is probing and pm_runtime_put_suppliers() will be called
* subsequently.
*
* Note that this doesn't prevent rpm_put_suppliers() from decreasing the link's
* rpm_active refcount down to one, so runtime suspend of the consumer end of
* @link is not affected.
*/
void pm_runtime_active_link(struct device_link *link, struct device *supplier)
{
refcount_add(2, &link->rpm_active);
pm_runtime_get_noresume(supplier);
}
void pm_runtime_drop_link(struct device *dev)
{
spin_lock_irq(&dev->power.lock);

1
include/linux/device.h
View file

@ -861,6 +861,7 @@ struct device_link {
#ifdef CONFIG_SRCU
struct rcu_head rcu_head;
#endif
bool supplier_preactivated; /* Owned by consumer probe. */
};
/**

4
include/linux/pm_runtime.h
View file

@ -59,8 +59,6 @@ extern void pm_runtime_clean_up_links(struct device *dev);
extern void pm_runtime_get_suppliers(struct device *dev);
extern void pm_runtime_put_suppliers(struct device *dev);
extern void pm_runtime_new_link(struct device *dev);
extern void pm_runtime_active_link(struct device_link *link,
struct device *supplier);
extern void pm_runtime_drop_link(struct device *dev);
static inline void pm_suspend_ignore_children(struct device *dev, bool enable)
@ -178,8 +176,6 @@ static inline void pm_runtime_clean_up_links(struct device *dev) {}
static inline void pm_runtime_get_suppliers(struct device *dev) {}
static inline void pm_runtime_put_suppliers(struct device *dev) {}
static inline void pm_runtime_new_link(struct device *dev) {}
static inline void pm_runtime_active_link(struct device_link *link,
struct device *supplier) {}
static inline void pm_runtime_drop_link(struct device *dev) {}
#endif /* !CONFIG_PM */