Re: [patch V4 part 1 30/36] lockdep: Always inline lockdep_{off,on}()

Mathieu Desnoyers
2020-05-13T23:46:42Z

----- On May 5, 2020, at 9:16 AM, Thomas Gleixner tglx@linutronix.de wrote:
[...]
> + * Split the recrursion counter in two to readily detect 'off' vs recursion.

recrursion -> recursion

> + */
> +#define LOCKDEP_RECURSION_BITS 16
> +#define LOCKDEP_OFF (1U << LOCKDEP_RECURSION_BITS)
> +#define LOCKDEP_RECURSION_MASK (LOCKDEP_OFF - 1)
> +
> +/*
> + * lockdep_{off,on}() are macros to avoid tracing and kprobes; not inlines due
> + * to header dependencies.
> + */
> +
> +#define lockdep_off() \
> +do { \
> + current->lockdep_recursion += LOCKDEP_OFF; \
> +} while (0)
> +
> +#define lockdep_on() \
> +do { \
> + current->lockdep_recursion -= LOCKDEP_OFF; \
> +} while (0)

Now that those on/off are macros rather than functions, I wonder if
adding compiler barriers would be relevant ?

Thanks,

Mathieu

>
> extern void lockdep_register_key(struct lock_class_key *key);
> extern void lockdep_unregister_key(struct lock_class_key *key);
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -393,25 +393,6 @@ void lockdep_init_task(struct task_struc
> task->lockdep_recursion = 0;
> }
>
> -/*
> - * Split the recrursion counter in two to readily detect 'off' vs recursion.
> - */
> -#define LOCKDEP_RECURSION_BITS 16
> -#define LOCKDEP_OFF (1U << LOCKDEP_RECURSION_BITS)
> -#define LOCKDEP_RECURSION_MASK (LOCKDEP_OFF - 1)
> -
> -void lockdep_off(void)
> -{
> - current->lockdep_recursion += LOCKDEP_OFF;
> -}
> -EXPORT_SYMBOL(lockdep_off);
> -
> -void lockdep_on(void)
> -{
> - current->lockdep_recursion -= LOCKDEP_OFF;
> -}
> -EXPORT_SYMBOL(lockdep_on);
> -
> static inline void lockdep_recursion_finish(void)
> {
> if (WARN_ON_ONCE(--current->lockdep_recursion))

--
Mathieu Desnoyers
EfficiOS Inc.