From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f70.google.com (mail-wm0-f70.google.com [74.125.82.70]) by kanga.kvack.org (Postfix) with ESMTP id 9B2776B0033 for ; Thu, 19 Oct 2017 05:41:51 -0400 (EDT) Received: by mail-wm0-f70.google.com with SMTP id t69so3211859wmt.7 for ; Thu, 19 Oct 2017 02:41:51 -0700 (PDT) Received: from mail-sor-f41.google.com (mail-sor-f41.google.com. [209.85.220.41]) by mx.google.com with SMTPS id g131sor274848wma.54.2017.10.19.02.41.50 for (Google Transport Security); Thu, 19 Oct 2017 02:41:50 -0700 (PDT) Date: Thu, 19 Oct 2017 11:41:47 +0200 From: Ingo Molnar Subject: Re: [PATCH 1/2] lockdep: Introduce CROSSRELEASE_STACK_TRACE and make it not unwind as default Message-ID: <20171019094147.n43gdh5fbp4rsjzc@gmail.com> References: <1508318006-2090-1-git-send-email-byungchul.park@lge.com> <20171018100944.g2mc6yorhtm5piom@gmail.com> <20171019043240.GA3310@X58A-UD3R> <20171019055730.mlpoz333ekflacs2@gmail.com> <20171019061112.GB3310@X58A-UD3R> <20171019062255.GC3310@X58A-UD3R> <20171019081053.2mmzzjgfwgtv5lz3@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: =?utf-8?B?77+92rrvv73Dti/vv73vv73vv73Tv++/ve+/ve+/ve+/ve+/vS9TVyBQbGF0?= =?utf-8?B?Zm9ybSjvv73vv70pQU9U77+977+9KGJ5dW5nY2h1bC5wYXJrQGxnZS5jb20p?= Cc: "peterz@infradead.org" , "tglx@linutronix.de" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "kernel-team@lge.com" , Linus Torvalds * i? 1/2 Uoi? 1/2 A?/i? 1/2 i? 1/2 i? 1/2 O?i? 1/2 i? 1/2 i? 1/2 i? 1/2 i? 1/2 /SW Platform(i? 1/2 i? 1/2 )AOTi? 1/2 i? 1/2 (byungchul.park@lge.com) wrote: > I don't want to pretend I'm perfect. Of course, I can make mistakes. > I'm just saying that *I have not seen* any crash by cross-release. > > In that case you pointed out, likewise, the crash was caused by ae813308f: > lockdep: Avoid creating redundant links, which is not related to the feature > actually. It was also falsely accused at the time again... > > Of course, it's my fault not to have made the design more robust so that > others can modify lockdep code caring less after cross-release commit. > That's what I'm sorry for. > > I already mentioned the above in the thread talking about the issue you > are pointing now. Of course, I basically appreciate all comments and > suggestions you have given, but you seem to have mis-understood some > issues wrt cross-release feature. Two different cross-release commits got bisected to with kernel crashes: Sep 30 kernel test rob | ce07a9415f ("locking/lockdep: Make check_prev_add() able to .."): BUG: unable to handle kernel NULL pointer dereference at 00000020 Oct 03 Fengguang Wu | [lockdep] b09be676e0 BUG: unable to handle kernel NULL pointer dereference at 000001f2 The first crash was bisected to: ce07a9415f26: locking/lockdep: Make check_prev_add() able to handle external stack_trace The second crash was bisected to: b09be676e0ff: locking/lockdep: Implement the 'crossrelease' feature ... and unless your argument that both bisections were bad, it doesn't matter where the root cause ended up being, fact is that it was not a problem free series and let's not pretend it was. Note that to me it *really* does not matter that a commit causes a crash: bugs happen, they are part of software development done by humans - so as long as it's not a pattern of underlying carelessness or some development process error it's not something to get emotional about. Ok? Thanks, Ingo -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org