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SubjectRe: [PATCH] [SCSI] scsi_pm: set device runtime state before parent suspended
On Thu, 5 Jul 2012, Lin Ming wrote:

> There is a race in scsi_bus_resume_common when set device's runtime
> state to active after pm_runtime_put_sync(dev->parent).
>
> Parent device may have been suspended so pm_runtime_set_active(dev) will
> fail with -EBUSY.
>
> Signed-off-by: Lin Ming <ming.m.lin@intel.com>
> CC: <stable@vger.kernel.org>
> ---
> drivers/scsi/scsi_pm.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/scsi/scsi_pm.c b/drivers/scsi/scsi_pm.c
> index d4201de..d2a80de 100644
> --- a/drivers/scsi/scsi_pm.c
> +++ b/drivers/scsi/scsi_pm.c
> @@ -85,14 +85,14 @@ static int scsi_bus_resume_common(struct device *dev)
> */
> pm_runtime_get_sync(dev->parent);
> err = scsi_dev_type_resume(dev);
> + if (err == 0) {
> + pm_runtime_disable(dev);
> + pm_runtime_set_active(dev);
> + pm_runtime_enable(dev);
> + }
> pm_runtime_put_sync(dev->parent);
> }
>
> - if (err == 0) {
> - pm_runtime_disable(dev);
> - pm_runtime_set_active(dev);
> - pm_runtime_enable(dev);
> - }

This isn't quite right. We still want to execute the
pm_runtime_disable, _set_active, and _enable even when
scsi_is_sdev_device(dev) is false.

I guess the revised code should look more like this:

/*
* Parent device may have runtime suspended as soon as
* it is woken up during the system resume.
*
* Resume it on behalf of child.
*/
pm_runtime_get_sync(dev->parent);

if (scsi_is_sdev_device(dev))
err = scsi_dev_type_resume(dev);
if (err == 0) {
pm_runtime_disable(dev);
pm_runtime_set_active(dev);
pm_runtime_enable(dev);
}

pm_runtime_put_sync(dev->parent);

Alan Stern



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