driver core: Extend device_is_dependent()

From: Rafael J. Wysocki <[email protected]>

If the device passed as the target (second argument) to device_is_dependent() is not completely registered (that is, it has been initialized, but not added yet), but the parent pointer of it is set, it may be missing from the list of the parent's children and device_for_each_child() called by device_is_dependent() cannot be relied on to catch that dependency.

For this reason, modify device_is_dependent() to check the ancestors of the target device by following its parent pointer in addition to the device_for_each_child() walk.

Fixes 9ed9895370ae ("driver core: Functional dependencies tracking support")

Signed-off-by Rafael J. Wysocki <[email protected]>

Reported-by Stephan Gerhold <[email protected]>

Tested-by Stephan Gerhold <[email protected]>

---

-> v2:
* Improve the changelog.
* Add a comment to explain the reason for the extra check.
* Add tags.

No code changes.

---
 drivers/base/core.c |   17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

Index: linux-pm/drivers/base/core.c
===================================================================

drivers/base/core.c +10 -0

@@ -208,6 +208,16 @@ int device_links_read_lock_held(void)
 #endif
 #endif /* !CONFIG_SRCU */
 
+static bool device_is_ancestor(struct device *dev, struct device *target)
+{
+       while (target->parent) {
+               target = target->parent;
+               if (dev == target)
+                       return true;
+       }
+       return false;
+}
+
 /**
  * device_is_dependent - Check if one device depends on another one
  * @dev: Device to check dependencies for.

@@ -221,7 +231,12 @@ int device_is_dependent(struct device *d
        struct device_link *link;
        int ret;
 

Quoted 65 lines · Rafael J. Wysocki

From: Rafael J. Wysocki <[email protected]>

If the device passed as the target (second argument) to device_is_dependent() is not completely registered (that is, it has been initialized, but not added yet), but the parent pointer of it is set, it may be missing from the list of the parent's children and device_for_each_child() called by device_is_dependent() cannot be relied on to catch that dependency.

For this reason, modify device_is_dependent() to check the ancestors of the target device by following its parent pointer in addition to the device_for_each_child() walk.

Fixes 9ed9895370ae ("driver core: Functional dependencies tracking support")

Signed-off-by Rafael J. Wysocki <[email protected]>

Reported-by Stephan Gerhold <[email protected]>

Tested-by Stephan Gerhold <[email protected]>

---

-> v2:
* Improve the changelog.
* Add a comment to explain the reason for the extra check.
* Add tags.

No code changes.

---
 drivers/base/core.c |   17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

Index: linux-pm/drivers/base/core.c
===================================================================

drivers/base/core.c +16 -1

@@ -208,6 +208,16 @@ int device_links_read_lock_held(void)
 #endif
 #endif /* !CONFIG_SRCU */
 
+static bool device_is_ancestor(struct device *dev, struct device *target)
+{
+       while (target->parent) {
+               target = target->parent;
+               if (dev == target)
+                       return true;
+       }
+       return false;
+}
+
 /**
  * device_is_dependent - Check if one device depends on another one
  * @dev: Device to check dependencies for.

@@ -221,7 +231,12 @@ int device_is_dependent(struct device *d
        struct device_link *link;
        int ret;
 
-       if (dev == target)
+       /*
+        * The "ancestors" check is needed to catch the case when the target
+        * device has not been completely initialized yet and it is still
+        * missing from the list of children of its parent device.
+        */
+       if (dev == target || device_is_ancestor(dev, target))
                return 1;
 

drivers/base/core.c int device_is_dependent(struct device *d · line 242

Quoted 2 lines

drivers/base/core.c +0 -0

        ret = device_for_each_child(dev, target, device_is_dependent);

Reviewed-by Saravana Kannan <[email protected]>

fw_devlink_relax_cycle() needs a similar fix. Want me to handle that as a separate patch to driver-core-next? Or do you want to combine that in this patch?

From: Rafael J. Wysocki <[email protected]>

If the device passed as the target (second argument) to device_is_dependent() is not completely registered (that is, it has been initialized, but not added yet), but the parent pointer of it is set, it may be missing from the list of the parent's children and device_for_each_child() called by device_is_dependent() cannot be relied on to catch that dependency.

For this reason, modify device_is_dependent() to check the ancestors of the target device by following its parent pointer in addition to the device_for_each_child() walk.

Fixes 9ed9895370ae ("driver core: Functional dependencies tracking support")

Signed-off-by Rafael J. Wysocki <[email protected]>

Reported-by Stephan Gerhold <[email protected]>

Tested-by Stephan Gerhold <[email protected]>

---

-> v2:
* Improve the changelog.
* Add a comment to explain the reason for the extra check.
* Add tags.

No code changes.

---
 drivers/base/core.c |   17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

Index: linux-pm/drivers/base/core.c
===================================================================

drivers/base/core.c +16 -1

@@ -208,6 +208,16 @@ int device_links_read_lock_held(void)
 #endif
 #endif /* !CONFIG_SRCU */
 
+static bool device_is_ancestor(struct device *dev, struct device *target)
+{
+       while (target->parent) {
+               target = target->parent;
+               if (dev == target)
+                       return true;
+       }
+       return false;
+}
+
 /**
  * device_is_dependent - Check if one device depends on another one
  * @dev: Device to check dependencies for.

@@ -221,7 +231,12 @@ int device_is_dependent(struct device *d
        struct device_link *link;
        int ret;
 
-       if (dev == target)
+       /*
+        * The "ancestors" check is needed to catch the case when the target
+        * device has not been completely initialized yet and it is still
+        * missing from the list of children of its parent device.
+        */
+       if (dev == target || device_is_ancestor(dev, target))
                return 1;
 
        ret = device_for_each_child(dev, target, device_is_dependent);

Quoted 14 lines · Rafael J. Wysocki

From: Rafael J. Wysocki <[email protected]>

If the device passed as the target (second argument) to device_is_dependent() is not completely registered (that is, it has been initialized, but not added yet), but the parent pointer of it is set, it may be missing from the list of the parent's children and device_for_each_child() called by device_is_dependent() cannot be relied on to catch that dependency.

For this reason, modify device_is_dependent() to check the ancestors of the target device by following its parent pointer in addition to the device_for_each_child() walk.

Quoted 4 lines

Fixes 9ed9895370ae ("driver core: Functional dependencies tracking support")

Signed-off-by Rafael J. Wysocki <[email protected]>

Reported-by Stephan Gerhold <[email protected]>

Tested-by Stephan Gerhold <[email protected]>

Greg, are you going to pick up this one or do you want me to take care of it?

It has been reviewed by Saravana.