From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linus Torvalds Subject: Re: linux-next: add utrace tree Date: Wed, 27 Jan 2010 03:04:58 -0800 (PST) Message-ID: References: <20100121013822.28781960.sfr@canb.auug.org.au> <20100122005147.GD22003@redhat.com> <20100121170541.7425ff10.akpm@linux-foundation.org> <20100122182827.GA13185@redhat.com> <20100122200129.GG22003@redhat.com> <20100122221348.GA4263@redhat.com> <1264575134.4283.1983.camel@laptop> <1264589716.4283.2006.camel@laptop> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Return-path: In-Reply-To: <1264589716.4283.2006.camel@laptop> Sender: linux-kernel-owner@vger.kernel.org To: Peter Zijlstra Cc: Tom Tromey , Kyle Moffett , "Frank Ch. Eigler" , Oleg Nesterov , Andrew Morton , Stephen Rothwell , Fr??d??ric Weisbecker , LKML , Steven Rostedt , Arnaldo Carvalho de Melo , linux-next@vger.kernel.org, "H. Peter Anvin" , utrace-devel@redhat.com, Thomas Gleixner , JimKeniston List-Id: linux-next.vger.kernel.org On Wed, 27 Jan 2010, Peter Zijlstra wrote: > > Right, so there's two aspects: > > 1) concurrency when inserting the probe That's the one I worried about. Stopping all threads will fix it, obviously at a disastrous performance cost, but what do I care? As noted, there are ways to do it safely with TLB switching, so it's fixable. > 2) concurrency when hitting the probe Yeah, I didn't worry about this part, since the only solution is the out-of-line one, and I don't much care how the memory gets allocated for it. Inserting a whole new vma seems pretty drastic, but compared to stopping all threads, it's a small thing. Linus