linux-kernel - Re: [RFC 10/12] x86, rwsem: simplify __down

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, 09 Jun 2016 15:40:58 +0100
From:	David Howells <dhowells@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	dhowells@...hat.com, Ingo Molnar <mingo@...nel.org>,
	Michal Hocko <mhocko@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	"David S. Miller" <davem@...emloft.net>,
	Tony Luck <tony.luck@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Chris Zankel <chris@...kel.net>,
	Max Filippov <jcmvbkbc@...il.com>, x86@...nel.org,
	linux-alpha@...r.kernel.org, linux-ia64@...r.kernel.org,
	linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
	sparclinux@...r.kernel.org, linux-xtensa@...ux-xtensa.org,
	linux-arch@...r.kernel.org, Michal Hocko <mhocko@...e.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Paul E. McKenney" <paulmck@...ibm.com>,
	Jason Low <jason.low2@....com>
Subject: Re: [RFC 10/12] x86, rwsem: simplify __down_write

Peter Zijlstra <peterz@...radead.org> wrote:

> Blergh; so looking at more asm there's still a few tricks we cannot do.
> So while overall size is down, some paths do end up more expensive. (It
> typically boils down to creative use of condition flags, which is very
> hard in C)

It can be done using ISO __atomic_fetch_add() and suchlike.

David