linux-kernel - Re: Subject: [PATCH] drivers-core: move device_pm_remove behind bus_remove

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Message-ID: <2338561.PDRRozbqko@vostro.rjw.lan>
Date:	Mon, 15 Oct 2012 22:59:28 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	yanmin_zhang@...ux.intel.com
Cc:	"Zhang, LongX" <longx.zhang@...el.com>,
	Alan Stern <stern@...land.harvard.edu>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pm@...ts.linux-foundation.org" 
	<linux-pm@...ts.linux-foundation.org>
Subject: Re: Subject: [PATCH] drivers-core: move device_pm_remove behind bus_remove_device

On Monday 15 of October 2012 15:39:49 Yanmin Zhang wrote:
> On Fri, 2012-09-21 at 01:58 +0000, Zhang, LongX wrote:
> > From: LongX Zhang <longx.zhang@...el.com>
> > 
> > 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 ingored. 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.
> The background about the patch: We hit an hang issue when removing a mmc
> device on Medfield Android phone by sysfs interface.
> 
> 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>

Can you please resend the patch?  I lost the track of it unfortunately.

Thanks,
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 5e6e00b..81ea7f2 100644
> > --- a/drivers/base/core.c
> > +++ b/drivers/base/core.c
> > @@ -1169,7 +1169,6 @@ 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);
> > @@ -1194,6 +1193,7 @@ 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);
> >  
> >  	/*
> 
> 
> 
-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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