linux-kernel - Re: [v3,11/41] mips: reuse asm-generic/barrier.h

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]

Date:	Thu, 14 Jan 2016 11:42:02 -0800
From:	Leonid Yegoshin <Leonid.Yegoshin@...tec.com>
To:	<paulmck@...ux.vnet.ibm.com>, Will Deacon <will.deacon@....com>
CC:	Peter Zijlstra <peterz@...radead.org>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	<linux-kernel@...r.kernel.org>, Arnd Bergmann <arnd@...db.de>,
	<linux-arch@...r.kernel.org>,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	<virtualization@...ts.linux-foundation.org>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	Joe Perches <joe@...ches.com>,
	David Miller <davem@...emloft.net>,
	<linux-ia64@...r.kernel.org>, <linuxppc-dev@...ts.ozlabs.org>,
	<linux-s390@...r.kernel.org>, <sparclinux@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-metag@...r.kernel.org>, <linux-mips@...ux-mips.org>,
	<x86@...nel.org>, <user-mode-linux-devel@...ts.sourceforge.net>,
	<adi-buildroot-devel@...ts.sourceforge.net>,
	<linux-sh@...r.kernel.org>, <linux-xtensa@...ux-xtensa.org>,
	<xen-devel@...ts.xenproject.org>,
	"Ralf Baechle" <ralf@...ux-mips.org>,
	Ingo Molnar <mingo@...nel.org>, <ddaney.cavm@...il.com>,
	<james.hogan@...tec.com>, Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [v3,11/41] mips: reuse asm-generic/barrier.h

On 01/14/2016 08:16 AM, Paul E. McKenney wrote:
> On Thu, Jan 14, 2016 at 12:04:45PM +0000, Will Deacon wrote:
>> On Wed, Jan 13, 2016 at 12:58:22PM -0800, Leonid Yegoshin wrote:
>>> On 01/13/2016 12:48 PM, Peter Zijlstra wrote:
>>>> On Wed, Jan 13, 2016 at 11:02:35AM -0800, Leonid Yegoshin wrote:
>>>>
>>>>> I ask HW team about it but I have a question - has it any relationship with
>>>>> replacing MIPS SYNC with lightweight SYNCs (SYNC_WMB etc)?
>>>> Of course. If you cannot explain the semantics of the primitives you
>>>> introduce, how can we judge the patch.
>>>>
>>>>
>>> You missed a point - it is a question about replacement of SYNC with
>>> lightweight primitives. It is NOT a question about multithread system
>>> behavior without any SYNC. The answer on a latest Will's question lies in
>>> different area.
> What Will said!
>
> Yes, you can cut corners within MIPS architecture-specific code,
> but primitives that are used in the core kernel really do need to
> work as expected.
>
> 							Thanx, Paul
>
>
Absolutelly! Please use SYNC - right now it is not.

An the only point - please use an appropriate SYNC_* barriers instead of 
heavy bold hammer. That stuff was design explicitly to support the 
requirements of Documentation/memory-barriers.txt

It is easy - just use smp_acquire instead of plain smp_mb 
insmp_load_acquire, at least for MIPS.

- Leonid.
- Leonid.