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[2a02:3100:a81d:e001:9c9b:db33:f166:fda]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4aa7f322c46sm196891285e9.2.2026.10.31.06.09.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 31 Oct 2026 06:09:44 -0700 (PDT) Date: Sat, 31 Oct 2026 14:09:42 +0100 From: Karl Mehltretter To: Andrew Morton Cc: Andrey Konovalov , Alexander Potapenko , Dmitry Vyukov , Marco Elver , Bradley Morgan , Anna-Maria Behnsen , Frederic Weisbecker , Thomas Gleixner , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , Sebastian Andrzej Siewior , Clark Williams , linux-rt-devel@lists.linux.dev, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 4/6] sched/core: Pause KCOV in __schedule() Message-ID: References: <20261005185803.39170-1-kmehltretter@gmail.com> <20261005185803.39170-5-kmehltretter@gmail.com> <20261030142354.bbc5e7f26fbfb6a8eee21290@linux-foundation.org> 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: <20261030142354.bbc5e7f26fbfb6a8eee21290@linux-foundation.org> On Fri, Oct 30, 2026 at 02:23:54PM +0100, Andrew Morton wrote: > __attribute__((no_instrument_function)) > __attribute__((__always_inline__)) > class_kcov_pause_t class_kcov_pause_constructor(void) > { > class_kcov_pause_t _t = { .lock = (void*)1 }, > *_T __attribute__((__unused__)) = &_t; > _T->paused = __kcov_pause(); > return _t; > } > > Adding all this goop to core scheduler functions on non-KCOV kernels > won't be terribly popular! > > A bit of macro magic can trivially make all this go away for non-KCOV > kernels. The overhead is probably acceptable with CONFIG_KCOV=y > kernels - seems it's only enabled for debug/research/fuzzing kernels. > > Ditto the hrtimer change. Aim to make these patches produce no change > in generated code with CONFIG_KCOV=n. > Good point. Leaving the guard outside #ifdef CONFIG_KCOV was an oversight in v2. I will fix this and the hrtimer wrapper in v5. Thanks, Karl