Re: [PATCH] posix-cpu-timers: Merge running and checking_timer state in one field

[Davidlohr Bueso]

On Tue, 20 Oct 2015, Frederic Weisbecker wrote:

> - * @checking_timer:	true when a thread in the group is in the
> - *			process of checking for thread group timers.
> - *
> + * @state:		flags describing the current state of the cputimer.
> + *			CPUTIMER_STATE_RUNNING bit means the timers is elapsing.

                                                             s/timers/timer

> + * 			CPUTIMER_STATE_CHECKING bit means that the cputimer has
> + *			expired and a thread in the group is checking the
> + *			callback list.

These comments might be better served when defining CPUTIMER_STATE_*

[...]

> @@ -606,7 +606,7 @@ bool posix_cpu_timers_can_stop_tick(struct task_struct *tsk)
> 		return false;
>
> 	/* Check if cputimer is running. This is accessed without locking. */
> -	if (READ_ONCE(tsk->signal->cputimer.running))
> +	if (READ_ONCE(tsk->signal->cputimer.state))
> 		return false;

Could we have cases, such as the above, where .state is set to CPUTIMER_STATE_CHECKING
and therefore the check is not equivalent?

Thanks,
Davidlohr
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