From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 743C4C61D85 for ; Tue, 21 Nov 2023 15:53:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234666AbjKUPx1 (ORCPT ); Tue, 21 Nov 2023 10:53:27 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59564 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234657AbjKUPxV (ORCPT ); Tue, 21 Nov 2023 10:53:21 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8B67D185; Tue, 21 Nov 2023 07:53:15 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=w97cVJb/aQInQREnjHpwi7QFE9oxzcwBFUlRXyXpLTM=; b=m93MnOeHJp3JuYMNkSzI0h+sh5 z10+8KAVJ91/7rNYnQBsLhrTDLx1pyFHMrAJfaMKirCS4WjNaxwUJvyCrzY/NG0ig0b//FNRDdupH VyDa1SgQ7G53XY5K7EfMksqVhEdxhd2Yix8bmQ99JaiPJJWOBWOeOi15EslMK7oOFvwWZbr/IyqsU I1Oir5kkvhZDF9P3Bn4fT58qS+rf2UZj91HCtCjGpuAwOa6j8KdSniVISY8dE8GB8r9Ttezlnnvry N1ECNDQXgVkUrnkVr3O0Xn4RAm+o7ZO876ARb3WHUNomBPAqXcuPOqcfOPvUf7rSjUWG+1sukH7Jn HMqwGzZA==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1r5T3a-005icl-2G; Tue, 21 Nov 2023 15:52:58 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 242B6300338; Tue, 21 Nov 2023 16:52:56 +0100 (CET) Date: Tue, 21 Nov 2023 16:52:56 +0100 From: Peter Zijlstra To: Mathieu Desnoyers Cc: "Paul E. McKenney" , Steven Rostedt , Masami Hiramatsu , linux-kernel@vger.kernel.org, Michael Jeanson , Alexei Starovoitov , Yonghong Song , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , bpf@vger.kernel.org, Joel Fernandes Subject: Re: [PATCH v4 1/5] tracing: Introduce faultable tracepoints Message-ID: <20231121155256.GN4779@noisy.programming.kicks-ass.net> References: <20231120205418.334172-2-mathieu.desnoyers@efficios.com> <20231120214742.GC8262@noisy.programming.kicks-ass.net> <62c6e37c-88cc-43f7-ac3f-1c14059277cc@paulmck-laptop> <20231120222311.GE8262@noisy.programming.kicks-ass.net> <20231121084706.GF8262@noisy.programming.kicks-ass.net> <20231121143647.GI8262@noisy.programming.kicks-ass.net> <6f503545-9c42-4d10-aca4-5332fd1097f3@efficios.com> <20231121144643.GJ8262@noisy.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231121144643.GJ8262@noisy.programming.kicks-ass.net> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 21, 2023 at 03:46:43PM +0100, Peter Zijlstra wrote: > Why is this such a hard question? Anyway, recapping from IRC: preemptible, SRCU: counter-array based, GP advances by increasing array index and waiting for previous index to drop to 0. notably, a GP can pass while a task is preempted but not within a critical section. SRCU has smp_mb() in the critical sections to improve GP. tasks: waits for every task to pass schedule() ensures that any pieces of text rendered unreachable before, is actually unused after. tasks-rude: like tasks, but different? build to handle tracing while rcu-idle, even though that was already deemed bad? tasks-tracing-rcu: extention of tasks to have critical-sections ? Should this simply be tasks? Can someone complete, please?