Re: [PATCH v4 01/27] lockdep: Teach lockdep about "USED" <- "IN-NMI" inversions

[Steven Rostedt]

On Fri, 21 Feb 2020 14:34:17 +0100
Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:

> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -379,13 +379,13 @@ void lockdep_init_task(struct task_struc
>  
>  void lockdep_off(void)
>  {
> -	current->lockdep_recursion++;
> +	current->lockdep_recursion += BIT(16);
>  }
>  EXPORT_SYMBOL(lockdep_off);
>  
>  void lockdep_on(void)
>  {
> -	current->lockdep_recursion--;
> +	current->lockdep_recursion -= BIT(16);
>  }
>  EXPORT_SYMBOL(lockdep_on);
>  

> +
> +static bool lockdep_nmi(void)
> +{
> +	if (current->lockdep_recursion & 0xFFFF)

Nitpick, but the association with bit 16 and this mask really should be
defined as a macro somewhere and not have hard coded numbers.

-- Steve

> +		return false;
> +
> +	if (!in_nmi())
> +		return false;
> +
> +	return true;
> +}
> +