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[2a02:3100:a81d:e001:9c9b:db33:f166:fda]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4abf67aa704sm117315545e9.8.2026.10.31.04.10.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 31 Oct 2026 04:10:47 -0700 (PDT) Date: Sat, 31 Oct 2026 12:10:45 +0100 From: Karl Mehltretter To: Peter Zijlstra Cc: Steven Rostedt , Thomas Gleixner , Sebastian Andrzej Siewior , Catalin Marinas , Will Deacon , Mark Rutland , Ingo Molnar , Andy Lutomirski , Frederic Weisbecker , "Paul E. McKenney" , Boqun Feng , Waiman Long , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , Hongyan Xia , Jonathan Corbet , Shuah Khan , Randy Dunlap , Andrew Morton , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , linux-arm-kernel@lists.infradead.org, linux-trace-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, linux-doc@vger.kernel.org, llvm@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH v2 03/13] sched: Split preempt-count bookkeeping from raw updates Message-ID: References: <20261028033127.82193-1-kmehltretter@gmail.com> <20261028033127.82193-4-kmehltretter@gmail.com> <20261029093219.GH1779021@noisy.programming.kicks-ass.net> X-Mailing-List: linux-rt-devel@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261029093219.GH1779021@noisy.programming.kicks-ass.net> On Thu, Oct 29, 2026 at 10:32:19AM +0100, Peter Zijlstra wrote: > Urgh, so much crazy. > > So WARNs in noinstr code are 'fine'. That is, they should not happen, if > they do, bad things have happened and we need the warning out ASAP, if > it takes the machine down, too bad. See the > instrumentation_{begin,end}() markers in x86 asm/bug.h. > > But yes, the tracing needs to go. But moving that around should not be > this ugly and also, that will give you the opportunity to fix > preempt_{en,dis}able_notrace(), since they currently also skip the bound > checks. Yes, that's a good direction. I checked the call chain and DEBUG_LOCKS_WARN_ON() is already fine in noinstr. arm64 just needs __always_inline on preempt_count() and should_resched() so Clang doesn't outline them. I will work on that. Thanks, Karl