* [PATCH v2] staging: gdm72xx: fix reference counting in gdm_wimax_event_init
@ 2012-07-24 14:49 Ben Chan
2012-07-25 4:50 ` devendra.aaru
0 siblings, 1 reply; 7+ messages in thread
From: Ben Chan @ 2012-07-24 14:49 UTC (permalink / raw)
To: Greg Kroah-Hartman
Cc: devel, linux-kernel, Devendra Naga, benchan, Dan Carpenter
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@chromium.org>
---
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
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH v2] staging: gdm72xx: fix reference counting in gdm_wimax_event_init
2012-07-24 14:49 [PATCH v2] staging: gdm72xx: fix reference counting in gdm_wimax_event_init Ben Chan
@ 2012-07-25 4:50 ` devendra.aaru
2012-07-25 13:53 ` Ben Chan
0 siblings, 1 reply; 7+ messages in thread
From: devendra.aaru @ 2012-07-25 4:50 UTC (permalink / raw)
To: Ben Chan; +Cc: Greg Kroah-Hartman, devel, linux-kernel, Dan Carpenter
On Tue, Jul 24, 2012 at 8:34 PM, Ben Chan <benchan@chromium.org> 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@chromium.org>
> ---
> 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,
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v2] staging: gdm72xx: fix reference counting in gdm_wimax_event_init
2012-07-25 4:50 ` devendra.aaru
@ 2012-07-25 13:53 ` Ben Chan
2012-08-08 19:50 ` Ben Chan
2012-08-10 4:30 ` devendra.aaru
0 siblings, 2 replies; 7+ messages in thread
From: Ben Chan @ 2012-07-25 13:53 UTC (permalink / raw)
To: devendra.aaru; +Cc: Greg Kroah-Hartman, devel, linux-kernel, Dan Carpenter
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@gmail.com> wrote:
> On Tue, Jul 24, 2012 at 8:34 PM, Ben Chan <benchan@chromium.org> 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@chromium.org>
>> ---
>> 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,
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v2] staging: gdm72xx: fix reference counting in gdm_wimax_event_init
2012-07-25 13:53 ` Ben Chan
@ 2012-08-08 19:50 ` Ben Chan
2012-08-10 4:30 ` devendra.aaru
1 sibling, 0 replies; 7+ messages in thread
From: Ben Chan @ 2012-08-08 19:50 UTC (permalink / raw)
To: devendra.aaru; +Cc: Greg Kroah-Hartman, devel, linux-kernel, Dan Carpenter
Hi,
Does patch v2 make sense?
Thanks,
Ben
On Wed, Jul 25, 2012 at 6:53 AM, Ben Chan <benchan@chromium.org> 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@gmail.com> wrote:
>> On Tue, Jul 24, 2012 at 8:34 PM, Ben Chan <benchan@chromium.org> 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@chromium.org>
>>> ---
>>> 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,
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v2] staging: gdm72xx: fix reference counting in gdm_wimax_event_init
2012-07-25 13:53 ` Ben Chan
2012-08-08 19:50 ` Ben Chan
@ 2012-08-10 4:30 ` devendra.aaru
2012-08-10 6:28 ` Dan Carpenter
1 sibling, 1 reply; 7+ messages in thread
From: devendra.aaru @ 2012-08-10 4:30 UTC (permalink / raw)
To: Ben Chan; +Cc: Greg Kroah-Hartman, devel, linux-kernel, Dan Carpenter
On Wed, Jul 25, 2012 at 7:23 PM, Ben Chan <benchan@chromium.org> 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.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v2] staging: gdm72xx: fix reference counting in gdm_wimax_event_init
2012-08-10 4:30 ` devendra.aaru
@ 2012-08-10 6:28 ` Dan Carpenter
2012-08-10 17:49 ` Ben Chan
0 siblings, 1 reply; 7+ messages in thread
From: Dan Carpenter @ 2012-08-10 6:28 UTC (permalink / raw)
To: devendra.aaru; +Cc: Ben Chan, Greg Kroah-Hartman, devel, linux-kernel
Ben, I'm confused. Do you have a way to test this, or are you just
doing manual review?
regards,
dan carpenter
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v2] staging: gdm72xx: fix reference counting in gdm_wimax_event_init
2012-08-10 6:28 ` Dan Carpenter
@ 2012-08-10 17:49 ` Ben Chan
0 siblings, 0 replies; 7+ messages in thread
From: Ben Chan @ 2012-08-10 17:49 UTC (permalink / raw)
To: Dan Carpenter; +Cc: devendra.aaru, Greg Kroah-Hartman, devel, linux-kernel
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 <dan.carpenter@oracle.com> wrote:
> Ben, I'm confused. Do you have a way to test this, or are you just
> doing manual review?
>
> regards,
> dan carpenter
>
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2012-08-10 17:49 UTC | newest]
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2012-07-24 14:49 [PATCH v2] staging: gdm72xx: fix reference counting in gdm_wimax_event_init Ben Chan
2012-07-25 4:50 ` devendra.aaru
2012-07-25 13:53 ` Ben Chan
2012-08-08 19:50 ` Ben Chan
2012-08-10 4:30 ` devendra.aaru
2012-08-10 6:28 ` Dan Carpenter
2012-08-10 17:49 ` Ben Chan
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