Hi,
Does patch v2 make sense?
Thanks,
Ben
On Wed, Jul 25, 2012 at 6:53 AM, Ben Chan <benchan@xxxxxxxxxxxx> 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
>
>
> On Tue, Jul 24, 2012 at 9:50 PM, devendra.aaru <devendra.aaru@xxxxxxxxx> wrote:
>> On Tue, Jul 24, 2012 at 8:34 PM, Ben Chan <benchan@xxxxxxxxxxxx> wrote:
>>> This patch fixes the commit "staging/gdm72xx: cleanup little at
>>> gdm_wimax_event_rcv" (8df858ea76b76dde9a39d4edd9aaded983582cfe),
>>> which mishandles the reference counting of wm_event.
>>>
>>> Signed-off-by: Ben Chan <benchan@xxxxxxxxxxxx>
>>> ---
>>> Fixed the commit message as suggested by Dan Carpenter.
>>>
>>> drivers/staging/gdm72xx/gdm_wimax.c | 16 ++++++++++------
>>> 1 files changed, 10 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/drivers/staging/gdm72xx/gdm_wimax.c b/drivers/staging/gdm72xx/gdm_wimax.c
>>> index 0716efc..6cb8107 100644
>>> --- a/drivers/staging/gdm72xx/gdm_wimax.c
>>> +++ b/drivers/staging/gdm72xx/gdm_wimax.c
>>> @@ -258,12 +258,16 @@ static int gdm_wimax_event_init(void)
>>> if (!wm_event.ref_cnt) {
>>> wm_event.sock = netlink_init(NETLINK_WIMAX,
>>> gdm_wimax_event_rcv);
>>> - if (wm_event.sock)
>>> - wm_event.ref_cnt++;
>>> - INIT_LIST_HEAD(&wm_event.evtq);
>>> - INIT_LIST_HEAD(&wm_event.freeq);
>>> - INIT_WORK(&wm_event.ws, __gdm_wimax_event_send);
>>> - spin_lock_init(&wm_event.evt_lock);
>>> + if (wm_event.sock) {
>>> + INIT_LIST_HEAD(&wm_event.evtq);
>>> + INIT_LIST_HEAD(&wm_event.freeq);
>>> + INIT_WORK(&wm_event.ws, __gdm_wimax_event_send);
>>> + spin_lock_init(&wm_event.evt_lock);
>>> + }
>>> + }
>>> +
>>> + if (wm_event.sock) {
>>> + wm_event.ref_cnt++;
>>> return 0;
>>> }
>>>
>>> --
>>> 1.7.7.3
>>>
>>
>> Hi Ben,
>>
>> I have some basic understanding about this flow of the function,
>>
>> Here is my understanding of the thing i have done when i was doing
>> some cleanups to this driver.
>>
>> The ref_cnt will be 0 at first time. if so the sock creation happens
>> only once, and register_wimax_device only calls this function.
>> so i think doing the ref_cnt++ inside the if (!wm_event.ref_cnt) is valid.
>>
>> Please suggest me if i am wrong.
>>
>> Thanks,
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