linux-kernel - Re: [RFT/RFC][PATCH] driver core: Fix PM-runtime for links added during consumer probe

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Message-ID: <eeaa7369-31bb-293e-e585-6014e4bcdd14@nvidia.com>
Date:   Tue, 19 Feb 2019 10:24:29 +0000
From:   Jon Hunter <jonathanh@...dia.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Ulf Hansson <ulf.hansson@...aro.org>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Daniel Vetter <daniel@...ll.ch>,
        Lukas Wunner <lukas@...ner.de>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Lucas Stach <l.stach@...gutronix.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        linux-tegra <linux-tegra@...r.kernel.org>
Subject: Re: [RFT/RFC][PATCH] driver core: Fix PM-runtime for links added
 during consumer probe


On 18/02/2019 22:08, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Commit 4c06c4e6cf63 ("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 4c06c4e6cf63 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.]
> 
> Fixes: 4c06c4e6cf63 ("driver core: Fix possible supplier PM-usage counter imbalance")
> Reported-by: Jon Hunter <jonathanh@...dia.com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> 
> On top of driver-core/driver-core-next.
> 
> Jon, Ulf, please test!

Thanks Rafael this works for me!

Tested-by: Jon Hunter <jonathanh@...dia.com>

Cheers
Jon

-- 
nvpublic