On Wed, Jul 25, 2012 at 7:23 PM, Ben Chan <[email protected]> wrote:
> Hi Devendra,
>
> Thanks for cleaning up the driver. If I understand the code
> correctly, the original author wanted to initialize wm_event once and
> reuse it for multiple devices, and thus reference counted it with
> ref_cnt.
>
> For instance, each time gdm_usb_probe() is called, it may call
> register_wimax_device() / gdm_wimax_event_init(). wm_event is
> initialized the first time when wm_event.ref_cnt == 0 (alternatively,
> the code could check !wm_event.sock). Subsequent calls to
> gdm_wimax_event_init() will simply increase the ref count. Similarly,
> gdm_usb_disconnect() calls unregister_wimax_device() /
> gdm_wimax_event_exit(), which decreases the ref count and disposes
> wm_event when ref_cnt becomes zero.
>
> The code change in commit 8df858ea76b76dde9a39d4edd9aaded983582cfe
> only prevents ref_cnt from increasing beyond one. So the code no
> longer work when there are multiple devices (i.e. wm_event could be
> disposed even when there is an active device).
>
> Thanks,
> Ben
>
>
Sorry Ben, I didn't saw the mail for a long time,
Thanks a lot for the long explanation, i will keep in mind of these
problems, and also i think your patch is ok.
Thanks,
Devendra.
Ben, I'm confused. Do you have a way to test this, or are you just
doing manual review?
regards,
dan carpenter
Hi Dan,
I manually walked through the driver code and spotted the issue. But
this morning I was able to get an extra module to verify my patch on
hardware.
I tested the following patterns using two identical modules, and
checked the creation/destruction/ref_cnt of wm_event:
- insert module A, remove A
- insert A, insert B, remove A, remove B
- insert A, insert B, remove B, remove A
- insert A, insert B, remove A, remove B
- insert A, insert B, remove B, insert B, remove B, remove A
Thanks,
Ben
On Thu, Aug 9, 2012 at 11:28 PM, Dan Carpenter <[email protected]> wrote:
> Ben, I'm confused. Do you have a way to test this, or are you just
> doing manual review?
>
> regards,
> dan carpenter
>