Re: [PATCH v2] drivers-core: move the calling to device_pm_removebehind the calling to bus_remove_device

From: Yanmin Zhang
Date: Sun Oct 21 2012 - 21:01:26 EST


On Tue, 2012-10-16 at 23:28 +0800, zhanglong wrote:
> We hit an hang issue when removing a mmc device on Medfield Android phone by sysfs interface.
>
> device_pm_remove will call pm_runtime_remove which would disable
> runtime PM of the device. After that pm_runtime_get* or
> pm_runtime_put* will be ignored. So if we disable the runtime PM
> before device really be removed, drivers' _remove callback may
> access HW even pm_runtime_get* fails. That is bad.
>
> Consider below call sequence when removing a device:
> device_del => device_pm_remove
> => class_intf->remove_dev(dev, class_intf) => pm_runtime_get_sync/put_sync
> => bus_remove_device => device_release_driver => pm_runtime_get_sync/put_sync
>
> remove_dev might call pm_runtime_get_sync/put_sync.
> Then, generic device_release_driver also calls pm_runtime_get_sync/put_sync.
> Since device_del => device_pm_remove firstly, later _get_sync wouldn't really wake up the device.
>
> I git log -p to find the patch which moves the calling to device_pm_remove ahead.
> It's below patch:
>
> commit 775b64d2b6ca37697de925f70799c710aab5849a
> Author: Rafael J. Wysocki <rjw@xxxxxxx>
> Date: Sat Jan 12 20:40:46 2008 +0100
>
> PM: Acquire device locks on suspend
>
> This patch reorganizes the way suspend and resume notifications are
> sent to drivers. The major changes are that now the PM core acquires
> every device semaphore before calling the methods, and calls to
> device_add() during suspends will fail, while calls to device_del()
> during suspends will block.
>
> It also provides a way to safely remove a suspended device with the
> help of the PM core, by using the device_pm_schedule_removal() callback
> introduced specifically for this purpose, and updates two drivers (msr
> and cpuid) that need to use it.
>
>
> As device_pm_schedule_removal is deleted by another patch, we need also revert other parts of the patch,
> i.e. move the calling of device_pm_remove after the calling to bus_remove_device.
>
> Signed-off-by: LongX Zhang <longx.zhang@xxxxxxxxx>
Rafael,

With the patch V2, is there anything else we could improve before it can
be merged into your testing tree?

Thanks,
Yanmin

> ---
> drivers/base/core.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index abea76c..150a415 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -1180,7 +1180,6 @@ void device_del(struct device *dev)
> if (dev->bus)
> blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
> BUS_NOTIFY_DEL_DEVICE, dev);
> - device_pm_remove(dev);
> dpm_sysfs_remove(dev);
> if (parent)
> klist_del(&dev->p->knode_parent);
> @@ -1205,6 +1204,7 @@ void device_del(struct device *dev)
> device_remove_file(dev, &uevent_attr);
> device_remove_attrs(dev);
> bus_remove_device(dev);
> + device_pm_remove(dev);
> driver_deferred_probe_del(dev);
>
> /* Notify the platform of the removal, in case they


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