Re: [PATCH] driver core: flush async calls before testing driver removal

[Dmitry Torokhov]

On Fri, Dec 9, 2016 at 4:15 PM, Vladimir Zapolskiy <vz@xxxxxxxxx> wrote:
> If CONFIG_DEBUG_TEST_DRIVER_REMOVE option is enabled a number of false
> positives are reported for ATA controller drivers, because ATA port
> probes are done asynchronously, and the same problem may also touch
> other asynchronously probed drivers.
>
> To reduce the rate of false reports on boot call async_synchronize_full()
> before attempting to remove a driver, the same is done in delete_module()
> syscall for all possible drivers and in __device_release_driver() function
> for asynchronously probed drivers.

I'd say CONFIG_DEBUG_TEST_DRIVER_REMOVE did what it was supposed to do
and uncovered a big in ATA drivers. Since driver core did not
asynchronously scheduled those actions it should not wait for their
completion either, but either ATA core or drivers should wait for
probing to complete before allowing remove() methods to run.

>
> Fixes: bea5b158ff0d ("driver core: add test of driver remove calls during probe")
> Suggested-by: Tejun Heo <tj@xxxxxxxxxx>
> Signed-off-by: Vladimir Zapolskiy <vz@xxxxxxxxx>
> ---
> Some time ago the issue was discussed on the linux-ide mailing list, see
>
>   https://www.spinics.net/lists/linux-ide/msg53481.html
>
>  drivers/base/dd.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index d76cd97..a4feecf 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -384,6 +384,8 @@ static int really_probe(struct device *dev, struct device_driver *drv)
>         if (test_remove) {
>                 test_remove = false;
>
> +               async_synchronize_full();
> +
>                 if (dev->bus->remove)
>                         dev->bus->remove(dev);
>                 else if (drv->remove)
> --
> 2.10.2
>

Thanks.

-- 
Dmitry