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SubjectRe: [PATCH] PM / runtime: Drop children check from __pm_runtime_set_status()
On Tue, Nov 28, 2017 at 11:58 AM, Geert Uytterhoeven
<geert@linux-m68k.org> wrote:
> Hi Rafael, Shimoda-san,
>
> On Sun, Nov 12, 2017 at 1:27 AM, Rafael J. Wysocki <rjw@rjwysocki.net> wrote:
>> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>>
>> The check for "active" children in __pm_runtime_set_status(), when
>> trying to set the parent device status to "suspended", doesn't
>> really make sense, because in fact it is not invalid to set the
>> status of a device with runtime PM disabled to "suspended" in any
>> case. It is invalid to enable runtime PM for a device with its
>> status set to "suspended" while its child_count reference counter
>> is nonzero, but the check in __pm_runtime_set_status() doesn't
>> really cover that situation.
>>
>> For this reason, drop the children check from __pm_runtime_set_status()
>> and add a check against child_count reference counters of "suspended"
>> devices to pm_runtime_enable().
>>
>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>> ---
>> drivers/base/power/runtime.c | 30 ++++++++++--------------------
>> 1 file changed, 10 insertions(+), 20 deletions(-)
>>
>> Index: linux-pm/drivers/base/power/runtime.c
>> ===================================================================
>> --- linux-pm.orig/drivers/base/power/runtime.c
>> +++ linux-pm/drivers/base/power/runtime.c
>> @@ -1101,29 +1101,13 @@ int __pm_runtime_set_status(struct devic
>> goto out;
>> }
>>
>> - if (dev->power.runtime_status == status)
>> + if (dev->power.runtime_status == status || !parent)
>> goto out_set;
>>
>> if (status == RPM_SUSPENDED) {
>> - /*
>> - * It is invalid to suspend a device with an active child,
>> - * unless it has been set to ignore its children.
>> - */
>> - if (!dev->power.ignore_children &&
>> - atomic_read(&dev->power.child_count)) {
>> - dev_err(dev, "runtime PM trying to suspend device but active child\n");
>
> JFTR, this triggered before during system resume on e.g. Salvator-XS with
> R-Car H3:
>
> ohci-platform ee080000.usb: runtime PM trying to suspend device
> but active child
> phy_rcar_gen3_usb2 ee080200.usb-phy: runtime PM trying to suspend
> device but active child
> ohci-platform ee0c0000.usb: runtime PM trying to suspend device
> but active child
> ohci-platform ee0a0000.usb: runtime PM trying to suspend device
> but active child
> phy_rcar_gen3_usb2 ee0c0200.usb-phy: runtime PM trying to suspend
> device but active child
> phy_rcar_gen3_usb2 ee0a0200.usb-phy: runtime PM trying to suspend
> device but active child
>
> so this was an existing issue with USB before.
>
>> - error = -EBUSY;
>> - goto out;
>> - }
>> -
>> - if (parent) {
>> - atomic_add_unless(&parent->power.child_count, -1, 0);
>> - notify_parent = !parent->power.ignore_children;
>> - }
>> - goto out_set;
>> - }
>> -
>> - if (parent) {
>> + atomic_add_unless(&parent->power.child_count, -1, 0);
>> + notify_parent = !parent->power.ignore_children;
>> + } else {
>> spin_lock_nested(&parent->power.lock, SINGLE_DEPTH_NESTING);
>>
>> /*
>> @@ -1307,6 +1291,12 @@ void pm_runtime_enable(struct device *de
>> else
>> dev_warn(dev, "Unbalanced %s!\n", __func__);
>>
>> + WARN(dev->power.runtime_status == RPM_SUSPENDED &&
>> + !dev->power.ignore_children &&
>> + atomic_read(&dev->power.child_count) > 0,
>> + "Enabling runtime PM for inactive device (%s) with active children\n",
>> + dev_name(dev));
>
> And now it became a bit more noisy:

Well, it's all existing issues, although the WARN() doesn't provide
additional information in this particular case.

I'm considering changing it to print a message without a stack trace.

Thanks,
Rafael

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