(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)
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.
Thanks,
Roland
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