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 PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Mon, 10 Sep 2007 15:38:23 +0100 From: Denys Vlasenko <vda.linux@...glemail.com> To: Arjan van de Ven <arjan@...radead.org> Cc: Linus Torvalds <torvalds@...ux-foundation.org>, Nick Piggin <piggin@...erone.com.au>, Satyam Sharma <satyam@...radead.org>, Herbert Xu <herbert@...dor.apana.org.au>, Paul Mackerras <paulus@...ba.org>, Christoph Lameter <clameter@....com>, Chris Snook <csnook@...hat.com>, Ilpo Jarvinen <ilpo.jarvinen@...sinki.fi>, "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>, Stefan Richter <stefanr@...6.in-berlin.de>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, linux-arch@...r.kernel.org, Netdev <netdev@...r.kernel.org>, Andrew Morton <akpm@...ux-foundation.org>, ak@...e.de, heiko.carstens@...ibm.com, David Miller <davem@...emloft.net>, schwidefsky@...ibm.com, wensong@...ux-vs.org, horms@...ge.net.au, wjiang@...ilience.com, cfriesen@...tel.com, zlynx@....org, rpjday@...dspring.com, jesper.juhl@...il.com, segher@...nel.crashing.org Subject: Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures On Monday 10 September 2007 15:51, Arjan van de Ven wrote: > On Mon, 10 Sep 2007 11:56:29 +0100 > Denys Vlasenko <vda.linux@...glemail.com> wrote: > > > > > Well, if you insist on having it again: > > > > Waiting for atomic value to be zero: > > > > while (atomic_read(&x)) > > continue; > > > > and this I would say is buggy code all the way. > > Not from a pure C level semantics, but from a "busy waiting is buggy" > semantics level and a "I'm inventing my own locking" semantics level. After inspecting arch/*, I cannot agree with you. Otherwise almost all major architectures use "conceptually buggy busy-waiting": arch/alpha arch/i386 arch/ia64 arch/m32r arch/mips arch/parisc arch/powerpc arch/sh arch/sparc64 arch/um arch/x86_64 All of the above contain busy-waiting on atomic_read. Including these loops without barriers: arch/mips/kernel/smtc.c while (atomic_read(&idle_hook_initialized) < 1000) ; arch/mips/sgi-ip27/ip27-nmi.c while (atomic_read(&nmied_cpus) != num_online_cpus()); [Well maybe num_online_cpus() is a barrier, I didn't check] arch/sh/kernel/smp.c if (wait) while (atomic_read(&smp_fn_call.finished) != (nr_cpus - 1)); Bugs? -- vda - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Powered by blists - more mailing lists