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 BBCCE1E22FC; Mon, 7 Jul 2025 14:22:11 +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=1751898131; cv=none; b=AUnkjAIa9qhNIdcTd3qxAg9FaeF06v1dQlm2pDlVa3i4KqrKvbhO0Mr1Ng7Qnl41oxYFDt6kWtuFm6KH0MYxDgRz/Oxo+pHZNanbwOTrmj4mOs+6TJTAoKHxkkALHYRakvgd5ulzuRmSHu5ZZJ3vUCMMkJ8IPF4af/1ptLTnx58= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751898131; c=relaxed/simple; bh=W7q8C3xrheSK5UsfA8zsgl5RRMzThIjledkWEDgN8pc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=M3AA3+qQyTfeGCGv9VeTnwAvgDpjfO3l3J8tYJQGKn1G0uj/dFM5XIZWmH2AlvPDsqqZq5mNjVC+qppr+ctyFmXo7ud2Hc+eDwVP7gtybbKvGGbLNhe53vgCcM+NryysPqvgzYNQozUY9TZELZWtoDE5MOmMaEPtTVdZUU/NhU4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=cf2xA0ir; 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="cf2xA0ir" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BB53DC4CEE3; Mon, 7 Jul 2025 14:22:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1751898131; bh=W7q8C3xrheSK5UsfA8zsgl5RRMzThIjledkWEDgN8pc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=cf2xA0irTVr7hr55mxRzLPweFG20hXbtXrAmidteADVg4vZcQwYxGJFjFwWOO1amS OlZvjd0a5YDvCheqcftIpQh+d7KAM87m55SSqCzvqwuQx4U1zPnzIoNQhIsxRi/iMV kqySdl35naZhUkA30JTWsCSb9NHC3EwGpOKrHUBeLwrIwnKyS1WImmM+8krKeDSe0C xjZysR/6g4J/1sIr3AG6HveeF2g/gqtomqIV4Wgmn89++bqW8zBoPxlHlb/9Vt7l6r gUKj5ifUdH/zTfvePKvaytNEswV/DF8AG8vM9q94EBmO8yAn3hSCDoaIRTWcYMBCkI 6ZhBE4UuUBtdA== Date: Mon, 7 Jul 2025 16:22:08 +0200 From: Frederic Weisbecker To: Joel Fernandes Cc: linux-kernel@vger.kernel.org, "Paul E. McKenney" , Neeraj Upadhyay , Josh Triplett , Boqun Feng , Uladzislau Rezki , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Jonathan Corbet , rcu@vger.kernel.org, linux-doc@vger.kernel.org Subject: Re: [PATCH] rcu: Document concurrent quiescent state reporting for offline CPUs Message-ID: References: <20250707033208.361677-1-joelagnelf@nvidia.com> Precedence: bulk X-Mailing-List: linux-doc@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: <20250707033208.361677-1-joelagnelf@nvidia.com> Le Sun, Jul 06, 2025 at 11:32:08PM -0400, Joel Fernandes a écrit : > The synchronization of CPU offlining with GP initialization is confusing > to put it mildly (rightfully so as the issue it deals with is complex). > Recent discussions brought up a question -- what prevents the > rcu_implicit_dyntick_qs() from warning about QS reports for offline > CPUs (missing QS reports for offline CPUs causing indefinite hangs). > > QS reporting for now-offline CPUs should only happen from: > - gp_init() > - rcutree_cpu_report_dead() > > Add some documentation on this and refer to it from comments in the code > explaining how QS reporting is not missed when these functions are > concurrently running. > > I referred heavily to this post [1] about the need for the ofl_lock. > [1] https://lore.kernel.org/all/20180924164443.GF4222@linux.ibm.com/ > > [ Applied paulmck feedback on moving documentation to Requirements.rst ] > > Link: https://lore.kernel.org/all/01b4d228-9416-43f8-a62e-124b92e8741a@paulmck-laptop/ > Co-developed-by: Paul E. McKenney > Signed-off-by: Joel Fernandes Very nice and welcome!!! Reviewed-by: Frederic Weisbecker -- Frederic Weisbecker SUSE Labs