linux-kernel - Re: [RFC PATCH 1/5] ACPI: Add acpi_lookup

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Date:	Thu, 06 Sep 2012 17:52:42 -0600
From:	Toshi Kani <toshi.kani@...com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	lenb@...nel.org, liuj97@...il.com, isimatu.yasuaki@...fujitsu.com
Subject: Re: [RFC PATCH 1/5] ACPI: Add acpi_lookup_driver() function

(snip)
 :
> > > +
> > > +       /* set HID to this device object */
> > > +       acpi_device_set_id(device);
> > > +
> > > +       /* lookup a matching driver */
> > > +       (void) bus_for_each_drv(device->dev.bus, NULL,
> > > +                                       device, acpi_match_driver);
> > > +       driver = device->driver;
> > 
> > This path is used when we receive a Notify to a device and a matching
> > driver has been registered, but the driver is not bound to the device.
> >  For example, it may be a newly-added device where we haven't bound a
> > driver to it yet.
> > 
> > Is there anything that prevents us from unloading the driver between
> > here (the point where we capture the "struct acpi_driver *") and the
> > point where we call "driver->ops.sys_notify"?
> 
> Hi Bjorn,
> 
> That's a very good question.  I will look into how we protect a driver
> from unloading when we try to attach & probe a driver in the
> acpi_add_single_object() path, and see if we can use a similar way to
> protect it here as well.

I have protected this path in version 2, which I just sent out.  It
calls .sys_notify() directly from bus_for_each_drv(), which protects the
driver entry by increasing its reference count while the callback
function is being called.

Thanks,
-Toshi
 



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