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From: Jason Gunthorpe <jgg@nvidia.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	kvm@vger.kernel.org, "Rafael J. Wysocki" <rafael@kernel.org>
Subject: Re: [PATCH 02/10] driver core: Pull required checks into driver_probe_device()
Date: Tue, 8 Jun 2021 09:21:58 -0300	[thread overview]
Message-ID: <20210608122158.GZ1002214@nvidia.com> (raw)
In-Reply-To: <YL8HLhJNFgIGfEQm@infradead.org>

On Tue, Jun 08, 2021 at 06:59:10AM +0100, Christoph Hellwig wrote:
> This looks good as-is, but a suggestions for incremental improvements
> below:
> 
> > @@ -1032,10 +1035,10 @@ int device_driver_attach(struct device_driver *drv, struct device *dev)
> >  	__device_driver_lock(dev, dev->parent);
> >  
> >  	/*
> > -	 * If device has been removed or someone has already successfully
> > -	 * bound a driver before us just skip the driver probe call.
> > +	 * If device someone has already successfully bound a driver before us
> > +	 * just skip the driver probe call.
> >  	 */
> > -	if (!dev->p->dead && !dev->driver)
> > +	if (!dev->driver)
> >  		ret = driver_probe_device(drv, dev);
> >  
> >  	__device_driver_unlock(dev, dev->parent);
> 
> It is kinda silly to keep the ->driver check here given that one caller
> completely ignores the return value, and the other turns a 0 return into
> -ENODEV anyway. 

Later patches revise this though, I think you noticed it

> So I think this check can go away, turning device_driver_attach into
> a trivial wrapper for driver_probe_device that adds locking, which
> might be useful to reflect in the naming.

I was scared to change this because "0 on already bound" is uAPI in
sysfs at this point.

And what you noticed in bind_store:

       dev = bus_find_device_by_name(bus, NULL, buf);
       if (dev && dev->driver == NULL && driver_match_device(drv, dev)) {
               err = device_driver_attach(drv, dev);

Seems troublesome as the driver_lock isn't held for that dev->driver
read.

So I'm inclined to delete the above, keep the check in
device_driver_attach and not change the uAPI?

Or the APIs need to be more complicated to support locked and unlocked
callers/etc

Jason

  reply	other threads:[~2021-06-08 12:22 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-08  0:55 [PATCH 00/10] Allow mdev drivers to directly create the vfio_device Jason Gunthorpe
2021-06-08  0:55 ` [Intel-gfx] " Jason Gunthorpe
2021-06-08  0:55 ` [PATCH 01/10] driver core: Do not continue searching for drivers if deferred probe is used Jason Gunthorpe
2021-06-08  5:51   ` Christoph Hellwig
2021-06-08  6:44   ` Greg Kroah-Hartman
2021-06-08 12:16     ` Jason Gunthorpe
2021-06-08 13:13       ` Greg Kroah-Hartman
2021-06-08 13:53         ` Jason Gunthorpe
2021-06-08  7:35   ` Greg Kroah-Hartman
2021-06-08 12:17     ` Jason Gunthorpe
2021-06-08  0:55 ` [PATCH 02/10] driver core: Pull required checks into driver_probe_device() Jason Gunthorpe
2021-06-08  5:59   ` Christoph Hellwig
2021-06-08 12:21     ` Jason Gunthorpe [this message]
2021-06-08  0:55 ` [PATCH 03/10] driver core: Flow the return code from ->probe() through to sysfs bind Jason Gunthorpe
2021-06-08  6:07   ` Christoph Hellwig
2021-06-08 23:53     ` Jason Gunthorpe
2021-06-08  6:47   ` Greg Kroah-Hartman
2021-06-08 12:30     ` Jason Gunthorpe
2021-06-08 13:16       ` Greg Kroah-Hartman
2021-06-08 14:03         ` Jason Gunthorpe
2021-06-08  0:55 ` [PATCH 04/10] driver core: Don't return EPROBE_DEFER to userspace during " Jason Gunthorpe
2021-06-08  6:14   ` Christoph Hellwig
2021-06-08  7:37   ` Greg Kroah-Hartman
2021-06-08  0:55 ` [PATCH 05/10] driver core: Export device_driver_attach() Jason Gunthorpe
2021-06-08  6:19   ` Christoph Hellwig
2021-06-08 12:33     ` Jason Gunthorpe
2021-06-08  0:55 ` [PATCH 06/10] vfio/mdev: Remove CONFIG_VFIO_MDEV_DEVICE Jason Gunthorpe
2021-06-08  0:55   ` [Intel-gfx] " Jason Gunthorpe
2021-06-08  6:20   ` Christoph Hellwig
2021-06-08  6:20     ` [Intel-gfx] " Christoph Hellwig
2021-06-11 12:40   ` Cornelia Huck
2021-06-11 12:40     ` [Intel-gfx] " Cornelia Huck
2021-06-14 12:35     ` Jason Gunthorpe
2021-06-14 12:35       ` [Intel-gfx] " Jason Gunthorpe
2021-06-14 12:35       ` Jason Gunthorpe
2021-06-08  0:55 ` [PATCH 07/10] vfio/mdev: Allow the mdev_parent_ops to specify the device driver to bind Jason Gunthorpe
2021-06-08  6:21   ` Christoph Hellwig
2021-06-08  0:55 ` [PATCH 08/10] vfio/mtty: Convert to use vfio_register_group_dev() Jason Gunthorpe
2021-06-08  0:55 ` [PATCH 09/10] vfio/mdpy: " Jason Gunthorpe
2021-06-08  0:55 ` [PATCH 10/10] vfio/mbochs: " Jason Gunthorpe
2021-06-08  6:22 ` [PATCH 00/10] Allow mdev drivers to directly create the vfio_device Christoph Hellwig
2021-06-08  6:22   ` [Intel-gfx] " Christoph Hellwig
2021-06-14 14:34 ` Kirti Wankhede
2021-06-14 14:34   ` [Intel-gfx] " Kirti Wankhede
2021-06-14 14:34   ` Kirti Wankhede
2021-06-14 14:36   ` Jason Gunthorpe
2021-06-14 14:36     ` [Intel-gfx] " Jason Gunthorpe
2021-06-14 14:36     ` Jason Gunthorpe

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