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

From	Oleg Nesterov <oleg@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2] signals: Avoid unnecessary taking of sighand->siglock
Date	2016-09-26 18:30 +0200
Message-ID	<slGWZ-67A-7@gated-at.bofh.it> (permalink)
References	<skBZo-6mq-11@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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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.

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[PATCH v2] signals: Avoid unnecessary taking of sighand->siglock Waiman Long <Waiman.Long@hpe.com> - 2016-09-23 19:00 +0200
  Re: [PATCH v2] signals: Avoid unnecessary taking of sighand->siglock Stas Sergeev <stsp@list.ru> - 2016-09-23 22:30 +0200
  Re: [PATCH v2] signals: Avoid unnecessary taking of sighand->siglock Oleg Nesterov <oleg@redhat.com> - 2016-09-26 18:30 +0200

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