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: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <alpine.LFD.1.10.0805181038020.3020@woody.linux-foundation.org>
Date:	Sun, 18 May 2008 10:40:23 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Oleg Nesterov <oleg@...sign.ru>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Austin Clements <amdragon+kernelbugzilla@....edu>,
	Ingo Molnar <mingo@...e.hu>, john stultz <johnstul@...ibm.com>,
	Michael Kerrisk <mtk.manpages@...glemail.com>,
	Roland McGrath <roland@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] posix timers: use SIGQUEUE_CANCELLED when the timer
 is destroyed



On Sun, 18 May 2008, Linus Torvalds wrote:
> 
> So the rule is that if one bit of a word needs locking, then they *all* 
> do.

Side note: the alternative, of course, is to just use the atomic bit 
operations. They aren't generally much (if at all) faster than locking + 
doing the operation + unlocking, but they can avoid lock contention, so 
if you do a lot of bit ops that need no other locking than the setting and 
clearing (possibly with testing), then they are the right choice.

For signals, we obviously need other locking, so the atomic bit ops are a 
waste of time (doing *both* locking for other reasons *and* atomic bitops 
is obviously much slower than either).

		Linus
--
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/

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ