linux-kernel - Re: [PATCH v2] drivers-core: move the calling to device_pm_remove behind the calling to bus_remove

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Message-ID: <1871387.QctMb7gSFB@vostro.rjw.lan>
Date:	Wed, 24 Oct 2012 21:46:19 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	zhanglong <longzhax@...el.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	yanmin_zhang@...ux.intel.com,
	Alan Stern <stern@...land.harvard.edu>,
	"linux-pm@...ts.linux-foundation.org" 
	<linux-pm@...ts.linux-foundation.org>
Subject: Re: [PATCH v2] drivers-core: move the calling to device_pm_remove behind the calling to bus_remove_device

On Tuesday 16 of October 2012 23:28:08 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@...k.pl>
> 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@...el.com>

Greg, do you see any potential problems with this patch?

Rafael


> ---
>  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
> 
-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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