From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oleg Nesterov Subject: Re: linux-next: add utrace tree Date: Wed, 27 Jan 2010 00:32:42 +0100 Message-ID: <20100126233242.GA25575@redhat.com> References: <877hr4g49l.fsf@basil.nowhere.org> <20100126210232.GF6567@basil.fritz.box> <20100126215349.GB19146@redhat.com> <20100126220301.GG6567@basil.fritz.box> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20100126220301.GG6567@basil.fritz.box> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: utrace-devel-bounces@redhat.com Errors-To: utrace-devel-bounces@redhat.com To: Andi Kleen Cc: Stephen Rothwell , Kyle Moffett , Arnaldo Carvalho de Melo , Peter Zijlstra , Peter Zijlstra , Fr??d??ric Weisbecker , LKML , Steven Rostedt , tromey@redhat.com, "Frank Ch. Eigler" , linux-next@vger.kernel.org, "H. Peter Anvin" , utrace-devel@redhat.com, Thomas Gleixner , Linus Torvalds List-Id: linux-next.vger.kernel.org On 01/26, Andi Kleen wrote: > > > Simple example. Try to debug/strace strace ot gdb itself. Not trivial, > > you can't attach to strace's tracees. Recently I spent 2 days trying to > > understand why strace -f hangs. I was able to attach to strace, but > > I wasn't able to see what its tracees do. > > But what would the semantics be inside the tracees even if you could? In this particular case, all I need was something like "gdb -p" to attach to the tracee, see the backtrace and detach. > > And, it was not possible to even trace strace until it hangs, with > > ptrace the tracee (strace) must stop to report the event and this > > shadowed the race. > > "Shadowing the race" was the second surname of strace I thought anyways @) > Basically if you care about races never use strace in the first place. Yes. And utrace doesn't require the tracee to be stopped to report the event ;) Yes, yes, utrace can't "fix" strace in this sense automatically, but still. Oleg.