On Tue, Apr 21, 2020 at 07:10:39PM -0700, Michel Lespinasse wrote:
> On Tue, Apr 21, 2020 at 5:14 PM Michel Lespinasse <walken@xxxxxxxxxx> wrote:
> > +static inline void mmap_assert_locked(struct mm_struct *mm)
> > +{
> > + if (IS_ENABLED(CONFIG_LOCKDEP) && debug_locks)
> > + VM_BUG_ON_MM(!lockdep_is_held(&mm->mmap_sem), mm);
> > + else
> > + VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm);
> > +}
>
> Turns out this function definition does not work for !CONFIG_LOCKDEP
> as lockdep_is_held is not defined in that case.
Oops, sorry. It only defines
#define lockdep_is_held_type(l, r) (1)
#define lockdep_assert_held(l) do { (void)(l); } while (0)
#define lockdep_assert_held_write(l) do { (void)(l); } while (0)
#define lockdep_assert_held_read(l) do { (void)(l); } while (0)
#define lockdep_assert_held_once(l) do { (void)(l); } while (0)
which seems like an oversight, but not one that you should be fixing.
> The following should work instead:
>
> static inline void mmap_assert_locked(struct mm_struct *mm)
> {
> #ifdef CONFIG_LOCKDEP
> if (debug_locks) {
> VM_BUG_ON_MM(!lockdep_is_held(&mm->mmap_lock), mm);
> return;
> }
> #endif
> VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_lock), mm);
> }
Yes, I agree.
