From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: linux-next: manual merge of the rcu tree with the tip tree Date: Tue, 1 Aug 2017 16:15:48 +0200 Message-ID: <20170801141548.mivo7du4nl26r7z3@hirez.programming.kicks-ass.net> References: <20170731135029.479025ea@canb.auug.org.au> <20170731161341.GG3730@linux.vnet.ibm.com> <1145333348.610.1501545845911.JavaMail.zimbra@efficios.com> <20170801040323.GP3730@linux.vnet.ibm.com> <20170801135849.t5nbcqotkhztr5mr@hirez.programming.kicks-ass.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20170801135849.t5nbcqotkhztr5mr@hirez.programming.kicks-ass.net> Sender: linux-kernel-owner@vger.kernel.org To: Andy Lutomirski Cc: "Paul E. McKenney" , Mathieu Desnoyers , Stephen Rothwell , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Linux-Next Mailing List , linux-kernel List-Id: linux-next.vger.kernel.org On Tue, Aug 01, 2017 at 03:58:49PM +0200, Peter Zijlstra wrote: > On Tue, Aug 01, 2017 at 06:43:14AM -0700, Andy Lutomirski wrote: > > Anyway, can you document whatever property you require with a comment > > in switch_mm() or wherever you're finding that property so that future > > arch changes don't break it? > > We need _a_ smp_mb after rq->curr store. x86 has plenty. That is, we need it when we change to a different !0 mm. And we have the mm_cpumask() atomics at the very least, even if loading a new CR3 would not be serializing.