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 CAE9323D29F; Tue, 25 Nov 2025 14:18:28 +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=1764080308; cv=none; b=RsrXBnhzhS1/Y5mZV+yXth3C+QnqgHJvXkD5+mxA8E3i94PvLeNcAdIsGPC4N2hwni5Bu8xyvZdtW6pSIZttrxdi/q91wx+5BZRT42XAS+mh5iK4R2tv0GDpxIj785WGuYPBYi8k2VmC4qfFw/nsO2K1I+lQdZSz3P7rCQGm/GE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764080308; c=relaxed/simple; bh=oPbcVTTzame3aqqLKrW9RY5mARPG0SFH+InJLmThENE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=P4GsAHw3tKmI0WlAXwrVicaxmqbWGr3dUq1rfKHkI0mvQ78uTPaiqlHkrnnsBr5BlHXcaa/vUlJIm5yUQ9tNL+bygvIpRnBjWZzoCwJgi7wjn8myg+XhVHH9UtOpyvpVvDnlVnUpH2qBFFFknWRQYc3Tk5lnaqYEtyi6Z3ykBoQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=oOfDQ2zI; 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="oOfDQ2zI" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CDC31C4CEF1; Tue, 25 Nov 2025 14:18:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1764080308; bh=oPbcVTTzame3aqqLKrW9RY5mARPG0SFH+InJLmThENE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=oOfDQ2zIj4Kmlt2P9IQw96sCrerj8kG1dKJbMHH2zRcM4XymK2i3pWtmNojt+nh0p MKqWGXKQz/Bp/9+cYvya2ZHKnv2PPenJPM0UHAtZvCxOKVZR9MReoMTleixFuG+9hp lPyuXFfcuvWZybvIyveWMMPkTUNsLNJ96nCjIfe5Owpe0OUcJXB8vCRQ+CHYvrqLca peE5rTILw0shnU18D+SUqrwnMQJoFJcssoxgC+Zve1sJbhywENac25BcParGTd5PLe V/d2P7XV6BUe0ElCUttjZFCz2KIRmgO5jUif+C3mnSvdlfna06/uKXLvc7JX9aRnl6 fyspEsSAmsyYA== Date: Tue, 25 Nov 2025 15:18:25 +0100 From: Frederic Weisbecker To: "Paul E. McKenney" Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, Andrii Nakryiko , Alexei Starovoitov , Peter Zijlstra , bpf@vger.kernel.org Subject: Re: [PATCH v2 14/16] srcu: Create an SRCU-fast-updown API Message-ID: References: <20251105203216.2701005-14-paulmck@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20251105203216.2701005-14-paulmck@kernel.org> Le Wed, Nov 05, 2025 at 12:32:14PM -0800, Paul E. McKenney a écrit : > This commit creates an SRCU-fast-updown API, including > DEFINE_SRCU_FAST_UPDOWN(), DEFINE_STATIC_SRCU_FAST_UPDOWN(), > __init_srcu_struct_fast_updown(), init_srcu_struct_fast_updown(), > srcu_read_lock_fast_updown(), srcu_read_unlock_fast_updown(), > __srcu_read_lock_fast_updown(), and __srcu_read_unlock_fast_updown(). > > These are initially identical to their SRCU-fast counterparts, but both > SRCU-fast and SRCU-fast-updown will be optimized in different directions > by later commits. SRCU-fast will lack any sort of srcu_down_read() and > srcu_up_read() APIs, which will enable extremely efficient NMI safety. > For its part, SRCU-fast-updown will not be NMI safe, which will enable > reasonably efficient implementations of srcu_down_read_fast() and > srcu_up_read_fast(). Doing a last round of reviews before sitting down on a pull request, I think the changelog in this one should mention what are the expected uses of SRCU-fast-updown, since the RCU-TASK-TRACE conversion bits aren't there for this merge window yet. Thanks. -- Frederic Weisbecker SUSE Labs