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
| ||
|
Date: Wed, 26 Jul 2017 08:46:15 -0700 From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> To: Will Deacon <will.deacon@....com> Cc: Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org, mingo@...nel.org, jiangshanlai@...il.com, dipankar@...ibm.com, akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com, josh@...htriplett.org, tglx@...utronix.de, rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com, fweisbec@...il.com, oleg@...hat.com Subject: Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option On Wed, Jul 26, 2017 at 10:36:46AM +0100, Will Deacon wrote: > On Tue, Jul 25, 2017 at 02:19:26PM -0700, Paul E. McKenney wrote: > > Some architectures are less precise than others in tracking which > > CPUs are running a given process due to ASIDs, though this is > > thought to be a non-problem: > > > > https://marc.info/?l=linux-arch&m=126716090413065&w=2 > > https://marc.info/?l=linux-arch&m=126716262815202&w=2 > > > > Thoughts? > > On arm64, we *never* touch mm_cpumask, so it will always be empty. The only > thing we could potentially use it for is non-broadcast TLB invalidation if > the mm was only active on a single CPU, but when I implemented that we > pretty much never hit that case. I was hoping fork()+exec() would trigger it > (e.g. scripts), but the scheduler treats both of those as rebalancing points > so the temporary ASID before the exec always has two CPUs set in its mask. OK, so it sounds like we should ignore ->mm_cpumask except possibly for an architecture-specific optimization, and rely solely on ->mm in the absence of such optimizations, right? Thanx, Paul
Powered by blists - more mailing lists