Messages in this thread | | | From | Saravana Kannan <> | Date | Mon, 18 Jan 2021 14:01:55 -0800 | Subject | Re: [PATCH v2] driver core: Extend device_is_dependent() |
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On Fri, Jan 15, 2021 at 10:30 AM Rafael J. Wysocki <rjw@rjwysocki.net> wrote: > > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > 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 <rafael.j.wysocki@intel.com> > Reported-by: Stephan Gerhold <stephan@gerhold.net> > Tested-by: Stephan Gerhold <stephan@gerhold.net> > --- > > -> 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 > =================================================================== > --- linux-pm.orig/drivers/base/core.c > +++ linux-pm/drivers/base/core.c > @@ -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); >
Reviewed-by: Saravana Kannan <saravanak@google.com>
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?
-Saravana
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