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: <52B338AA.1020307@zytor.com>
Date:	Thu, 19 Dec 2013 10:19:22 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Ingo Molnar <mingo@...nel.org>
CC:	Peter Zijlstra <peterz@...radead.org>, Len Brown <lenb@...nel.org>,
	x86@...nel.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, Len Brown <len.brown@...el.com>,
	stable@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Mike Galbraith <efault@....de>, Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH] x86 idle: repair large-server 50-watt idle-power regression

On 12/19/2013 10:09 AM, H. Peter Anvin wrote:
> On 12/19/2013 09:07 AM, Ingo Molnar wrote:
>>
>> Likewise, having a barrier before the MONITOR looks sensible as well. 
>> Having it _after_ monitor looks weird and is probably wrong. [It might 
>> have been the effects of someone seeing the spurious wakeup problems 
>> with realizing the true source, or so.]
>>
> 
> Does anyone know the history of this barrier after the monitor?  I know
> Len is looking for a minimal patchset that can go into -stable, and it
> seems prudent to not preturb the code more than necessary, but going
> forward it would be nice to know...
> 

Hmm... it *looks* like it is intended to be part of the construct:

	smp_mb();
	if (!need_resched())
		...

I found a note in the HLT variant of the function saying:

/*
 * TS_POLLING-cleared state must be visible before we
 * test NEED_RESCHED:
 */

... which presumably has been copied elsewhere.

	-hpa


--
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