Re: [PATCH 10/11] sched: Debug nested sleeps

Oleg Nesterov
2014-09-29T22:17:05Z

On 09/24, Peter Zijlstra wrote:
>
> +#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
> +
> +#define __set_task_state(tsk, state_value) \
> + do { \
> + (tsk)->task_state_change = _THIS_IP_; \
> + (tsk)->state = (state_value); \
> + } while (0)

...

> @@ -7143,6 +7143,19 @@ void __might_sleep(const char *file, int
> {
> static unsigned long prev_jiffy; /* ratelimiting */
>
> + /*
> + * Blocking primitives will set (and therefore destroy) current->state,
> + * since we will exit with TASK_RUNNING make sure we enter with it,
> + * otherwise we will destroy state.
> + */
> + if (WARN(current->state != TASK_RUNNING,
> + "do not call blocking ops when !TASK_RUNNING; "
> + "state=%lx set at [<%p>] %pS\n",
> + current->state,
> + (void *)current->task_state_change,
> + (void *)current->task_state_change))
> + __set_current_state(TASK_RUNNING);

Question: now that we have ->task_state_change, perhaps it makes sense
to redefine fixup_sleep()

#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
#define fixup_sleep() (current->task_state_change = 0)
#else
#define fixup_sleep() do { } while (0)
#endif

and make the WARN() above depend on task_state_change != 0 ?

This is minor, but this way CONFIG_DEBUG_ATOMIC_SLEEP will not imply
a subtle behavioural change.

Oleg.