From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0E6C0DF59; Thu, 18 Sep 2025 16:13:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=216.40.44.16 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758212008; cv=none; b=HrjQ1HVtE0edd/lHatUZS4R51DabCeEZbHfeRHgs5Yx1FmRUyPqV9TIJcgESKpIlhuHE0RJUG2lBNSkxXGl/qNVbyvO2Pwe+/xxZTxIoCkvS3inEIbu1qF/AylwroJVRjw2ZvtNR/wleT9D1gA9xqn853pQ3z2BDZo0ZQ4T50Qo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758212008; c=relaxed/simple; bh=RkkHYldHqxfCy+eO9kZc2Nu88Vb/p3AF9OgOx7ZCEAQ=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=NNqs8aIlnoX7xicHSXDduoCGWQTGQpyMhhph/j9lqeCAuRHf7I4ARqkb20t9rHcAEZodMyCHqer4Gf895xODVTRqARdGbFHjwBmhs0nwM+e6CwyI2FITbhYSmseWdN9K1ifml9lGHAO08vM5T/c4A9VBHJqP/L9ck8ktQYvRGaI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org; spf=pass smtp.mailfrom=goodmis.org; arc=none smtp.client-ip=216.40.44.16 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=goodmis.org Received: from omf15.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 0D508118E89; Thu, 18 Sep 2025 16:13:21 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf15.hostedemail.com (Postfix) with ESMTPA id 2846618; Thu, 18 Sep 2025 16:13:08 +0000 (UTC) Date: Thu, 18 Sep 2025 12:14:16 -0400 From: Steven Rostedt To: Bart Van Assche Cc: Ian Rogers , Marco Elver , Peter Zijlstra , Boqun Feng , Ingo Molnar , Will Deacon , "David S. Miller" , Luc Van Oostenryck , "Paul E. McKenney" , Alexander Potapenko , Arnd Bergmann , Bill Wendling , Christoph Hellwig , Dmitry Vyukov , Eric Dumazet , Frederic Weisbecker , Greg Kroah-Hartman , Herbert Xu , Jann Horn , Joel Fernandes , Jonathan Corbet , Josh Triplett , Justin Stitt , Kees Cook , Kentaro Takeda , Lukas Bulwahn , Mark Rutland , Mathieu Desnoyers , Miguel Ojeda , Nathan Chancellor , Neeraj Upadhyay , Nick Desaulniers , Tetsuo Handa , Thomas Gleixner , Thomas Graf , Uladzislau Rezki , Waiman Long , kasan-dev@googlegroups.com, linux-crypto@vger.kernel.org, linux-doc@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-security-module@vger.kernel.org, linux-sparse@vger.kernel.org, llvm@lists.linux.dev, rcu@vger.kernel.org Subject: Re: [PATCH v3 02/35] compiler-capability-analysis: Add infrastructure for Clang's capability analysis Message-ID: <20250918121416.19a8041e@gandalf.local.home> In-Reply-To: <1ca90ba0-7bdc-43d1-af12-bba73dd3234a@acm.org> References: <20250918140451.1289454-1-elver@google.com> <20250918140451.1289454-3-elver@google.com> <1ca90ba0-7bdc-43d1-af12-bba73dd3234a@acm.org> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-sparse@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspamout04 X-Rspamd-Queue-Id: 2846618 X-Stat-Signature: jk37s4n4y1abypzz3ibjma6i8hwh3dpi X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX187tFXsL5Le7f+OEdXPb8EfevPMdYJjxao= X-HE-Tag: 1758211988-794253 X-HE-Meta: U2FsdGVkX19m1tAn22PHk3kX2Wk2POBgAZFzgAQIMCx/TzKCFJHSRgy7lqGNU4t4JpUf2LxrofFc8Ml/SzvQUemqI2s/M2eVv2TcCTTofn0gFGf1qiKnggle2+rBi9jozqgLP+w5zmTzD8j5BYGNETdC7HYpSCmlxzgRl1HmUDgT6vBPRbNQKlew/GiSPntamWI4BN+3BQMlrQzHKrw2Hd44nH0TJbDzGUvq4EnHN5l77wWkx8yamYKm0wF/UonjU1auAq1+e+AHgLIMHgDBTy/q+l9/HvzB2gWDjclvwsnGTS+Jv2LDmjZbgWOiLNXP1sp9TafIX1LTwyRs55KIsTFDvD2gur62c5R5bpv6t02yJBvS9Pt6FACmEbxkfSaUp1nLcDU5Q19B7Ha8v33a91ClwZlXoj1UYYAtqvo6OkbX+GZwbhQ0RoFfAYIW3JVWEzxWKbCA0qFysRVjwJOtsFC2FqAYNCgDAkEhxNFg1LQ= On Thu, 18 Sep 2025 09:03:17 -0700 Bart Van Assche wrote: > On 9/18/25 8:58 AM, Ian Rogers wrote: > > On Thu, Sep 18, 2025 at 7:05=E2=80=AFAM Marco Elver = wrote: =20 > >> +config WARN_CAPABILITY_ANALYSIS > >> + bool "Compiler capability-analysis warnings" > >> + depends on CC_IS_CLANG && CLANG_VERSION >=3D 220000 > >> + # Branch profiling re-defines "if", which messes with the comp= iler's > >> + # ability to analyze __cond_acquires(..), resulting in false p= ositives. > >> + depends on !TRACE_BRANCH_PROFILING =20 > >=20 > > Err, wow! What and huh, and why? Crikes. I'm amazed you found such an > > option exists. I must be very naive to have never heard of it and now > > I wonder if it is needed and load bearing? =20 >=20 > (+Steven) >=20 > This is an old option. I think this commit introduced it: >=20 > commit 52f232cb720a7babb752849cbc2cab2d24021209 > Author: Steven Rostedt > Date: Wed Nov 12 00:14:40 2008 -0500 >=20 > tracing: likely/unlikely branch annotation tracer >=20 I still use it every year (enable it during December for a few weeks on my workstation and server) and post the results publicly. When I get time, I try to fix (add / remove) likely/unlikely statements. Unfortunately, I haven't had time to look deeper at them. https://rostedt.org/branches/current/ This year I missed December and ended up running it in January instead. -- Steve