Re: [PATCH 1/2] mlx4: remove unnecessary pci_set_drvdata()

On Tue, Aug 15, 2017 at 10:13:36AM +0300, Leon Romanovsky wrote:

On Tue, Aug 15, 2017 at 02:33:05AM -0400, Zhu Yanjun wrote:

quoted

The driver core clears the driver data to NULL after device_release
or on probe failure. Thus, it is not necessary to manually clear the
device driver data to NULL.

It makes sense and I'm pretty sure that you are right, but I'm failing
to find the function in device core which sets it to NULL. Can you help
me and present the actual call stack to that code place?

http://elixir.free-electrons.com/linux/v4.13-rc1/source/drivers/base/dd.c#L840

The call to the remove callback is on line 833.

This is done after dropping devres, so you could allocate the drv data
inside a devm object and everything would unwind correctly.

In this case, the kfree is explicit, so I would advocate for still putting
the null near the kfree to minimize the time where a free'd pointer is
present - eg incase a devm callback or some other bug accidently
touches it.

Jason