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

[Jon Hunter]

On 18/02/2019 22:08, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> 
> 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@xxxxxxxxxx>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> ---
> 
> On top of driver-core/driver-core-next.
> 
> Jon, Ulf, please test!

Thanks Rafael this works for me!

Tested-by: Jon Hunter <jonathanh@xxxxxxxxxx>

Cheers
Jon

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