From: Rob Herring <robh@kernel.org>
To: Saravana Kannan <saravanak@google.com>
Cc: Frank Rowand <frowand.list@gmail.com>,
Rob Herring <robh+dt@kernel.org>,
"Rafael J. Wysocki" <rafael@kernel.org>,
kernel-team@android.com, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
John Stultz <john.stultz@linaro.org>
Subject: Re: [PATCH v2 2/2] of: property: Improve cycle detection when one of the devices is never added
Date: Wed, 17 Jun 2020 16:12:21 -0600 [thread overview]
Message-ID: <20200617221221.GA2923473@bogus> (raw)
In-Reply-To: <20200610011934.49795-3-saravanak@google.com>
On Tue, 09 Jun 2020 18:19:34 -0700, Saravana Kannan wrote:
> Consider this example where -> means LHS device is a consumer of RHS
> device and indentation represents "child of" of the previous device.
>
> Device A -> Device C
>
> Device B -> Device A
> Device C
>
> Without this commit:
> 1. Device A is added.
> 2. Device A is added to waiting for supplier list (Device C)
> 3. Device B is added
> 4. Device B is linked as a consumer to Device A
> 5. Device A doesn't probe because it's waiting for Device C to be added.
> 6. Device B doesn't probe because Device A hasn't probed.
> 7. Device C will never be added because it's parent hasn't probed.
>
> So, Device A, B and C will be in a probe/add deadlock.
>
> This commit detects this scenario and stops trying to create a device
> link between Device A and Device C since doing so would create the
> following cycle:
> Device A -> Devic C -(parent)-> Device B -> Device A.
>
> With this commit:
> 1. Device A is added.
> 3. Device B is added
> 4. Device B is linked as a consumer to Device A
> 5. Device A probes.
> 6. Device B probes because Device A has probed.
> 7. Device C is added and probed.
>
> Signed-off-by: Saravana Kannan <saravanak@google.com>
> ---
> drivers/of/property.c | 62 ++++++++++++++++++++++++++++++++++++++-----
> 1 file changed, 56 insertions(+), 6 deletions(-)
>
Both patches applied.
Rob
next prev parent reply other threads:[~2020-06-17 22:12 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-10 1:19 [PATCH v2 0/2] fw_devlink: Improve cycle detection in DT Saravana Kannan
2020-06-10 1:19 ` [PATCH v2 1/2] driver core: Add device_is_dependent() to linux/device.h Saravana Kannan
2020-06-10 1:19 ` [PATCH v2 2/2] of: property: Improve cycle detection when one of the devices is never added Saravana Kannan
2020-06-17 22:12 ` Rob Herring [this message]
2020-06-18 1:13 ` Saravana Kannan
2020-06-10 4:47 ` [PATCH v2 0/2] fw_devlink: Improve cycle detection in DT John Stultz
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