Re: [HPDD-discuss] [PATCH 4/4] Staging: lustre: sparse lock warning fix
On Wed, May 20, 2015 at 04:51:59PM +0000, Dilger, Andreas wrote:
On 2015/05/18, 3:21 PM, "Dan Carpenter"
<dan.carpenter(a)oracle.com> wrote:
>On Mon, May 18, 2015 at 08:34:51PM +0200, Adrian Remonda wrote:
>> Fixed sparse warning: context imbalance in 'nrs_resource_put_safe' -
>> 'different lock contexts for basic block' by releasing the lock on each
>> iteration of the for loop.
>>
>
>That changelog doesn't sound correct at all. That's not a correct
>motivation or explanation.
>
>I reviewed the patch and it's likely going to cause dead locks. The code
>is trying to take the spinlock for the first pointer in the array and
>release it at the end. Now it takes the first pointer's spinlock a
>bunch of times (dead lock) and releases it once (will not happen because
>we are already dead).
It isn't clear to me what the checkpatch complaint actually means? Is it
that the spin_lock() and spin_unlock() calls have different amounts of
indentation?
It's not a checkpatch.pl warning, it's a Sparse warning. Sparse is
crappy at reporting locking bugs. It's mostly false positives.
I think it's saying that some paths lock and unlock some don't.
Smatch is also fairly crappy at finding locking bugs, unfortunately.
I need to re-write it using modern features and cross function analysis.
regards,
dan carpenter