On Tue, Oct 02, 2018 at 02:52:23PM -0700, Bart Van Assche wrote:
> Since __device_release_driver() is called with the device lock held
> and since the same device lock is obtained by the functions that
> perform asynchronous probing (driver_attach_async() and
> __device_attach_async_helper()), asynchronous probing is already
> serialized against __device_release_driver(). Remove the
> async_synchronize_full() call from __device_release_driver() to
> avoid that a deadlock is triggered.
Hmm, I see. Well, the idea was to let all outstanding async probes
(scheduled but not yet running) to complete before releasing the driver.
I am not sure if anyone actually needs this behavior and implementing it
in deadlock free way is nigh impossible, so
Acked-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
>
> See also commit 765230b5f084 ("driver-core: add asynchronous probing
> support for drivers").
Should probably be "Fixes: 765230b5f084 ..."
>
> Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
> Cc: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
> Cc: Lee Duncan <lduncan@xxxxxxxx>
> Cc: Hannes Reinecke <hare@xxxxxxxx>
> Cc: Luis R. Rodriguez <mcgrof@xxxxxxxx>
> Cc: Johannes Thumshirn <jthumshirn@xxxxxxx>
> Cc: Christoph Hellwig <hch@xxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> ---
> drivers/base/dd.c | 3 ---
> 1 file changed, 3 deletions(-)
>
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index edfc9f0b1180..d6520de659bd 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -926,9 +926,6 @@ static void __device_release_driver(struct device *dev, struct device *parent)
>
> drv = dev->driver;
> if (drv) {
> - if (driver_allows_async_probing(drv))
> - async_synchronize_full();
> -
> while (device_links_busy(dev)) {
> device_unlock(dev);
> if (parent)
> --
> 2.19.0.605.g01d371f741-goog
>
Thanks.
--
Dmitry
