From: "Rafael J. Wysocki" <rafael@kernel.org>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Linux PM <linux-pm@vger.kernel.org>,
Stephan Gerhold <stephan@gerhold.net>,
Saravana Kannan <saravanak@google.com>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>
Subject: Re: [PATCH v2] driver core: Extend device_is_dependent()
Date: Tue, 19 Jan 2021 16:09:14 +0100 [thread overview]
Message-ID: <CAJZ5v0gccJKSVuN-okBnvHPjNYJ_FbkzfOueb=AUDr2xHaL7Xg@mail.gmail.com> (raw)
In-Reply-To: <17705994.d592GUb2YH@kreacher>
On Fri, Jan 15, 2021 at 7:31 PM 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>
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.
> ---
>
> -> 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);
>
>
>
next prev parent reply other threads:[~2021-01-19 18:29 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-15 18:30 [PATCH v2] driver core: Extend device_is_dependent() Rafael J. Wysocki
2021-01-18 22:01 ` Saravana Kannan
2021-01-19 13:23 ` Rafael J. Wysocki
2021-01-19 15:09 ` Rafael J. Wysocki [this message]
2021-01-19 15:21 ` Greg Kroah-Hartman
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