* Roland Dreier <[email protected]> wrote:
> (Ingo -- you seem to be the last person to touch all this stuff, and I
> can't untangle what you did, hence I'm sending this email to you)
>
> On at least some of my configs on x86_64, when running sparse, I see
> bogus 'warning: context imbalance in '<func>' - wrong count at exit'.
>
> This seems to be because I have CONFIG_SMP=y, CONFIG_DEBUG_SPINLOCK=n
> and CONFIG_PREEMPT=n. Therefore, <linux/spinlock.h> does
>
> #define spin_lock(lock) _spin_lock(lock)
>
> which picks up
>
> void __lockfunc _spin_lock(spinlock_t *lock) __acquires(lock);
>
> from <linux/spinlock_api_smp.h>, but <linux/spinlock.h> also has:
>
> #if defined(CONFIG_DEBUG_SPINLOCK) || defined(CONFIG_PREEMPT) || \
> !defined(CONFIG_SMP)
> //...
> #else
> # define spin_unlock(lock) __raw_spin_unlock(&(lock)->raw_lock)
this is the direct-inlining speedup some people insisted on.
> and <asm-x86_64/spinlock.h> has:
>
> static inline void __raw_spin_unlock(raw_spinlock_t *lock)
> {
> asm volatile("movl $1,%0" :"=m" (lock->slock) :: "memory");
> }
>
> so sparse doesn't see any __releases() to match the __acquires.
>
> This all seems to go back to commit bda98685 ("x86: inline spin_unlock
> if !CONFIG_DEBUG_SPINLOCK and !CONFIG_PREEMPT") but I don't know what
> motivated that change.
>
> Anyway, Ingo or anyone else, what's the best way to fix this? Maybe
> the right way to fix this is just to define away __acquires/__releases
> unless CONFIG_DEBUG_SPINLOCK is set, but that seems suboptimal.
i think the right way to fix it might be to define a _spin_unlock()
within those #ifdef branches, and then to define spin_lock as:
static inline void spin_lock(spinlock_t *lock) __acquires(lock)
{
_spin_lock(lock);
}
?
Ingo
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