linux-kernel - Re: Do we really need curr_target in signal

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20140129145535.GA12562@redhat.com>
Date:	Wed, 29 Jan 2014 15:55:35 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Rakib Mullick <rakib.mullick@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: Do we really need curr_target in signal_struct ?

On 01/29, Rakib Mullick wrote:
>
> On Tue, Jan 28, 2014 at 10:43 PM, Oleg Nesterov <oleg@...hat.com> wrote:
>
> > But I guess ->curr_target was added exactly to avoid this loop if
> > possible, assuming that wants_signal(->current_targer) should be
> > likely true. Although perhaps this optimization is too simple.
> >
> Well, this code block will only hit when first check for wants_signal()
> will miss,

Yes,

> that means we need to find some other thread of the group.

Yes,

> AFAIU, ->current_target is only a loop breaker to avoid infinite loop,

No. It caches the last result of "find a thread which can handle this
group-wide signal".

> but - by using while_each_thread() we can remove it completely, thus
> helps to get rid from maintaining it too.

... and remove the optimization above.

> I'll prepare a proper patch with you suggestions for reviewing.

I am not sure we want this patch. Once again, I do not know how much
->curr_target helps, and certainaly it can't help always. But you
should not blindly remove it just because yes, sure, it is not strictly
needed to find a wants_signal() thread.

Oleg.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/