On Thursday, July 19, 2018 7:14:58 AM CEST Pingfan Liu wrote:
> There is a race window in device_shutdown(), which may cause
> -1. parent device shut down before child or
> -2. no shutdown on a new probing device.
>
> For 1st, taking the following scenario:
> device_shutdown new plugin device
> list_del_init(parent_dev);
> spin_unlock(list_lock);
> device_add(child)
> probe child
> shutdown parent_dev
> --> now child is on the tail of devices_kset
>
> For 2nd, taking the following scenario:
> device_shutdown new plugin device
> device_add(dev)
> device_lock(dev);
> ...
> device_unlock(dev);
> probe dev
> --> now, the new occurred dev has no opportunity to shutdown
>
> To fix this race issue, just prevent the new probing request. With this
> logic, device_shutdown() is more similar to dpm_prepare().
Right.
This still doesn't prevent new children of a device from being added during
shutdown (something like the PM ->prepare callback would be needed for that),
but at least it prevents drivers from binding to the new devices.
Reviewed-by: Rafael J. Wysocki <raf...@kernel.org>
> Cc: Rafael J. Wysocki <r...@rjwysocki.net>
> Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org>
> Signed-off-by: Pingfan Liu <kernelf...@gmail.com>
> ---
> drivers/base/core.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index df3e1a4..3aba4ad 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -2809,6 +2809,9 @@ void device_shutdown(void)
> {
> struct device *dev, *parent;
>
> + wait_for_device_probe();
> + device_block_probing();
> +
> spin_lock(&devices_kset->list_lock);
> /*
> * Walk the devices list backward, shutting down each in turn.
>
