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SubjectRe: [PATCH] driver core: Move deferred devices to the end of dpm_list before probing
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On Thursday, July 05, 2012, Mark Brown wrote:
> When deferred probe was originally added the idea was that devices which
> defer their probes would move themselves to the end of dpm_list in order
> to try to keep the assumptions that we're making about the list being in
> roughly the order things should be suspended correct. However this hasn't
> been what's been happening and doing it requires a lot of duplicated code
> to do the moves.
>
> Instead take a simple, brute force solution and have the deferred probe
> code push devices to the end of dpm_list before it retries the probe. This
> does mean we lock the dpm_list a bit more often but it's very simple and
> the code shouldn't be a fast path. We do the move with the deferred mutex
> dropped since doing things with fewer locks held simultaneously seems like
> a good idea.
>
> This approach was most recently suggested by Grant Likely.
>
> Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

Looks good.

Acked-by: Rafael J. Wysocki <rjw@sisk.pl>

> ---
> drivers/base/dd.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index 6cd2c6c..9b0aca4 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -85,8 +85,20 @@ static void deferred_probe_work_func(struct work_struct *work)
> * manipulate the deferred list
> */
> mutex_unlock(&deferred_probe_mutex);
> +
> + /*
> + * Force the device to the end of the dpm_list since
> + * the PM code assumes that the order we add things to
> + * the list is a good order for suspend but deferred
> + * probe makes that very unsafe.
> + */
> + device_pm_lock();
> + device_pm_move_last(dev);
> + device_pm_unlock();
> +
> dev_dbg(dev, "Retrying from deferred list\n");
> bus_probe_device(dev);
> +
> mutex_lock(&deferred_probe_mutex);
>
> put_device(dev);
>



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