From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 121062FCE12; Thu, 17 Jul 2025 16:27:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752769656; cv=none; b=rj+dIc6D8OQloIAuno1VE9WKfwhQwL7FWfmNFfSAP/tF3KM81Kxh5rR73FDQZ3SbuMShkiEvacABP2zTm1OTk7Sl+Cdgt3OP5NaH1EywRErI8OWRLjSyspiFWGG56q6OF8PmSDk6Yz0qGN1lqaWXYJxAXsdGRhre6jtjDHdlBEA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752769656; c=relaxed/simple; bh=T6IDN6DNaQO447cutHK+OtFjUXY+Qu5JPigU282jM1s=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=VuryVaMU+Afk2YtmCj1cgipF9vINjFckfO07w5Oqby0lpjwmWKPSdBdcuhkIOCehxxJ/Vh9ijmRVunFzGjtrZyBzuC6o5+oXNDB6nL3wrq2NwA7VoXY9GfvVVpcltADjd5lWVCQ4BZ+L4J4biAQnYGaHMwh6s8pVdxtDbfwJ1Ns= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=a48SC85F; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="a48SC85F" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 561A8C4CEF0; Thu, 17 Jul 2025 16:27:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1752769655; bh=T6IDN6DNaQO447cutHK+OtFjUXY+Qu5JPigU282jM1s=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=a48SC85FDMY07QgHo+q3jYkPuas5/szTj/achK2TFqdIYUOk8ZIyP1DCknSlhBznK BmhGrTP17YC4dqchFuTIb5r/gsE3SyYl90+gCDVk0zzXeW5g4Ou4HCgo2U5rwLa89q uj8U+SvRQHtzBuL1L2LXoanfYwNURPntUI0BjCtZP8z8I0C6g/AzBFtCwvqWVj2HEk WXZZPO0ABVVhgxLQSXFWHPVUYIndL0moMJJElgTNyPomfSmtCFdmn8VvdLpHdblh05 K/W5mOpS3+QdQ9XPoJOTumGOLZkmyow2vFIbArVicnOAy81hjR3cV/BqAnEwoxorRb hNcEWuXYjSq/Q== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id CDF26CE09F5; Thu, 17 Jul 2025 09:27:34 -0700 (PDT) Date: Thu, 17 Jul 2025 09:27:34 -0700 From: "Paul E. McKenney" To: Steven Rostedt Cc: Steven Rostedt , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, bpf@vger.kernel.org, x86@kernel.org, Masami Hiramatsu , Mathieu Desnoyers , Josh Poimboeuf , Peter Zijlstra , Ingo Molnar , Jiri Olsa , Namhyung Kim , Thomas Gleixner , Andrii Nakryiko , Indu Bhagat , "Jose E. Marchesi" , Beau Belgrave , Jens Remus , Linus Torvalds , Andrew Morton , Jens Axboe , Florian Weimer , Sam James Subject: Re: [PATCH v14 09/12] unwind deferred: Use SRCU unwind_deferred_task_work() Message-ID: Reply-To: paulmck@kernel.org References: <20250717004910.297898999@kernel.org> <20250717004957.918908732@kernel.org> <47c3b0df-9f11-4e14-97e2-0f3ba3b09855@paulmck-laptop> <20250717082526.7173106a@gandalf.local.home> <41c204c0-eabc-4f4f-93f4-2568e2f962a9@paulmck-laptop> <20250717121010.4246366a@batman.local.home> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250717121010.4246366a@batman.local.home> On Thu, Jul 17, 2025 at 12:10:10PM -0400, Steven Rostedt wrote: > On Thu, 17 Jul 2025 08:48:40 -0700 > "Paul E. McKenney" wrote: > > > So if there is some reason that you absolutely cannot immediately convert > > to SRCU-fast, let's please discuss. > > There's two reasons I wouldn't add it immediately. > > One, is the guard(srcu_fast) isn't in mainline yet. I would either need > to open code it, or play the tricks of basing code off your tree. Fair point! But guard(srcu_fast) isn't in my tree, either, just guard(srcu_fast_nopreempt). So why not add guard(srcu_fast) in your tree, and we can ack it. Yes, that means we will have a merge conflict at some point, but it will be a trivial one. > Two, I'm still grasping at the concept of srcu_fast (and srcu_lite for > that matter), where I rather be slow and safe than optimize and be > unsafe. The code where this is used may be faulting in user space > memory, so it doesn't need the micro-optimizations now. Straight-up SRCU and guard(srcu), then? Both are already in mainline. Or are those read-side smp_mb() calls a no-go for this code? Thanx, Paul