Hi,
Sparse reports the following:
CHECK drivers/staging/rtl8188eu/core/rtw_mlme.c
drivers/staging/rtl8188eu/core/rtw_mlme.c:1003:9: warning: context imbalance in
'rtw_free_assoc_resources' - different lock contexts for basic block
The code in question is as follows:
if (lock_scanned_queue)
spin_lock_bh(&(pmlmepriv->scanned_queue.lock));
pwlan = rtw_find_network(&pmlmepriv->scanned_queue,
tgt_network->network.MacAddress);
if (lock_scanned_queue)
spin_unlock_bh(&(pmlmepriv->scanned_queue.lock));
As this fragment uses the identical test to unlock that is used to lock, and the
test variable is not touched, I think this is a false indication. I am using
version 0.4.4 of sparse.
Thanks,
Larry
On Wed, Oct 16, 2013 at 10:23:56PM -0500, Larry Finger wrote:
> Sparse reports the following:
>
> CHECK drivers/staging/rtl8188eu/core/rtw_mlme.c
> drivers/staging/rtl8188eu/core/rtw_mlme.c:1003:9: warning: context
> imbalance in 'rtw_free_assoc_resources' - different lock contexts
> for basic block
>
> The code in question is as follows:
>
> if (lock_scanned_queue)
> spin_lock_bh(&(pmlmepriv->scanned_queue.lock));
>
> pwlan = rtw_find_network(&pmlmepriv->scanned_queue,
> tgt_network->network.MacAddress);
>
> if (lock_scanned_queue)
> spin_unlock_bh(&(pmlmepriv->scanned_queue.lock));
>
> As this fragment uses the identical test to unlock that is used to
> lock, and the test variable is not touched, I think this is a false
> indication. I am using version 0.4.4 of sparse.
Sparse can't track conditional contexts like this; sparse intentionally
complains here that you're running the same basic block (the
rtw_find_network call) with and without a lock held.
The following workaround works when this is legitimate, though it isn't
ideal:
if (condition) {
lock
do_thing
unlock
} else {
do_thing
}
Ideally, Sparse should be able to track conditional contexts, but that
would require some form of abstract evaluation, or as a simplistic hack,
looking for identical side-effect-free conditional expressions.
- Josh Triplett
On 10/17/2013 11:25 AM, Josh Triplett wrote:
> On Wed, Oct 16, 2013 at 10:23:56PM -0500, Larry Finger wrote:
>> Sparse reports the following:
>>
>> CHECK drivers/staging/rtl8188eu/core/rtw_mlme.c
>> drivers/staging/rtl8188eu/core/rtw_mlme.c:1003:9: warning: context
>> imbalance in 'rtw_free_assoc_resources' - different lock contexts
>> for basic block
>>
>> The code in question is as follows:
>>
>> if (lock_scanned_queue)
>> spin_lock_bh(&(pmlmepriv->scanned_queue.lock));
>>
>> pwlan = rtw_find_network(&pmlmepriv->scanned_queue,
>> tgt_network->network.MacAddress);
>>
>> if (lock_scanned_queue)
>> spin_unlock_bh(&(pmlmepriv->scanned_queue.lock));
>>
>> As this fragment uses the identical test to unlock that is used to
>> lock, and the test variable is not touched, I think this is a false
>> indication. I am using version 0.4.4 of sparse.
>
> Sparse can't track conditional contexts like this; sparse intentionally
> complains here that you're running the same basic block (the
> rtw_find_network call) with and without a lock held.
>
> The following workaround works when this is legitimate, though it isn't
> ideal:
>
> if (condition) {
> lock
> do_thing
> unlock
> } else {
> do_thing
> }
>
> Ideally, Sparse should be able to track conditional contexts, but that
> would require some form of abstract evaluation, or as a simplistic hack,
> looking for identical side-effect-free conditional expressions.
Thanks for the answer, which is about what I expected. Sparse is a great tool,
particularly for endian-related issues.
Larry