platform/surface: dtx: Fix poll function

The poll function should not return -ERESTARTSYS.

Furthermore, locking in this function is completely unnecessary. The
ddev->lock protects access to the main device and controller (ddev->dev
and ddev->ctrl), ensuring that both are and remain valid while being
accessed by clients. Both are, however, never accessed in the poll
function. The shutdown test (via atomic bit flags) be safely done
without locking, so drop locking here entirely.

Reported-by: kernel test robot <lkp@intel.com>
Fixes: 1d609992832e ("platform/surface: Add DTX driver)
Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
Link: https://lore.kernel.org/r/20210513134437.2431022-1-luzmaximilian@gmail.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

diff --git a/drivers/platform/surface/surface_dtx.c b/drivers/platform/surface/surface_dtx.c
index 63ce587e79e3ba2470778b2dfc5386dfcb0d8ea4..5d9b758a99bbc8c8a2616406ece312db8d3f615b 100644 (file)
--- a/drivers/platform/surface/surface_dtx.c
+++ b/drivers/platform/surface/surface_dtx.c
@@ -527,20 +527,14 @@ static __poll_t surface_dtx_poll(struct file *file, struct poll_table_struct *pt
        struct sdtx_client *client = file->private_data;
        __poll_t events = 0;
 
-       if (down_read_killable(&client->ddev->lock))
-               return -ERESTARTSYS;
-
-       if (test_bit(SDTX_DEVICE_SHUTDOWN_BIT, &client->ddev->flags)) {
-               up_read(&client->ddev->lock);
+       if (test_bit(SDTX_DEVICE_SHUTDOWN_BIT, &client->ddev->flags))
                return EPOLLHUP | EPOLLERR;
-       }
 
        poll_wait(file, &client->ddev->waitq, pt);
 
        if (!kfifo_is_empty(&client->buffer))
                events |= EPOLLIN | EPOLLRDNORM;
 
-       up_read(&client->ddev->lock);
        return events;
 }