Is this a preempt issue in drivers/input/evdev.c

[Yin,Fengwei]

Hi,
When open/close evdev, the code is as following to handle multi-client
operation:
static int evdev_release(...)
{
        ...
        if (!--evdev->open) {
                <------------preempted
                if (evdev->exist)
                        input_close_device(...);
                else
                        evdev_free(evdev);
        }
        return 0;
}

static int evdev_open(...)
{
        ...
        if (!evdev->open++ && evdev->exist)｛
                errror = input_open_device(...);
                if (error) {
                        ...
                }
        }
        ...
        return 0;
}

So if the evdev_release() is preempted at the point marked by another
process which will open the evdev, which will make operation sequence
like:

   --evdev->open in evdev_release()
         -----> preempted
                                    evdev->open++ and input_open_devie()
         <----- reschedule 
        input_close_device()

Should we introduce a mutex here? Or do I miss something? Thanks.

Regards
Yin, Fengwei


        



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