Context imbalance false positive

Context imbalance false positive

[Luis R. Rodriguez]

I'm not sure how to resolve a situation like this:

#include <linux/module.h>
#include <linux/spinlock.h>

MODULE_AUTHOR("Luis R. Rodriguez");
MODULE_LICENSE("GPL");

static spinlock_t some_lock;

static void lock(int bh_flag)
{
        if (bh_flag)
                spin_lock_bh(&some_lock);
        else
                spin_lock(&some_lock);
}

static void unlock(int bh_flag)
{
        if (bh_flag)
                spin_unlock_bh(&some_lock);
        else
                spin_unlock(&some_lock);
}

static int hello_init(void)
{
        spin_lock_init(&some_lock);
        lock(1);
        printk("I am a module, cheers!\n");
        unlock(1);
        return 0;
}

static void goodbye_exit(void)
{
        printk("Goodbye cruel world!\n");
}

module_init(hello_init);
module_exit(goodbye_exit);

----

Sparse complains with:
/home/mcgrof/devel/spin_lock_sparse/sparse_spinlock.c:14:3: warning:
context imbalance in 'lock': wrong count at exit
/home/mcgrof/devel/spin_lock_sparse/sparse_spinlock.c:14:3:    context
'lock': wanted 0, got 1
/home/mcgrof/devel/spin_lock_sparse/sparse_spinlock.c:20:3: warning:
context problem in 'unlock': '_spin_unlock_bh' expected different
context
/home/mcgrof/devel/spin_lock_sparse/sparse_spinlock.c:20:3:    context
'lock': wanted >= 1, got 0

You can test compile from files here:

http://ruslug.rutgers.edu/~mcgrof/spin_lock_sparse/

  Luis

Re: Context imbalance false positive

[Johannes Berg]

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On Thu, 2008-07-17 at 16:52 -0700, Luis R. Rodriguez wrote:
> I'm not sure how to resolve a situation like this:

> static void lock(int bh_flag)
> {
>         if (bh_flag)
>                 spin_lock_bh(&some_lock);
>         else
>                 spin_lock(&some_lock);

The only generally accepted way is to not program locking dependent on
flags.

You can sneak in sparse annotations to do it anyway, but I won't tell
you how :)

johannes

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Re: Context imbalance false positive

[Luis R. Rodriguez]

On Fri, Jul 18, 2008 at 1:25 AM, Johannes Berg
<johannes@sipsolutions.net> wrote:
> On Thu, 2008-07-17 at 16:52 -0700, Luis R. Rodriguez wrote:
>> I'm not sure how to resolve a situation like this:
>
>> static void lock(int bh_flag)
>> {
>>         if (bh_flag)
>>                 spin_lock_bh(&some_lock);
>>         else
>>                 spin_lock(&some_lock);
>
> The only generally accepted way is to not program locking dependent on
> flags.

Agreed, and that's what I'm trying to do actually. I think the above
is pure absolute garbage.

> You can sneak in sparse annotations to do it anyway, but I won't tell
> you how :)

If you mean by __acquires() and __releases() then that didn't help.

  Luis