Re: [PATCH v2] signals: Avoid unnecessary taking of sighand->siglock

[Oleg Nesterov]

On 09/23, Waiman Long wrote:
>
>  
> +	/*
> +	 * In case the signal mask hasn't changed, we won't need to take
> +	 * the lock. The current blocked mask can be modified by other CPUs.
> +	 * To be safe, we need to do an atomic read without lock. As a result,
> +	 * this check will only be done on 64-bit architectures.
> +	 */
> +	if ((_NSIG_WORDS == 1) &&
> +	    (READ_ONCE(tsk->blocked.sig[0]) == newset->sig[0]))
> +		return;

so in case you missed my reply to V1, I still think that the comment is wrong
and you should drop the _NSIG_WORDS check.

Oleg.