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 4D8D9269823 for ; Wed, 25 Jun 2025 14:42:23 +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=1750862544; cv=none; b=IfId9FFBiGheKD57+HWr4oXXXm4iYyaORdVNHBCH4Zs2AeXjo0YGr0AvkBzxFcZfxr9BI9bonLvalypA1r+5o7J041wCcJd2HdMvzyQEqeunRxfcatktHiauAii1iiabnVglTvVfdga9QYrxuoWI69Q+j3tGARxhLb+MpLX8krA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750862544; c=relaxed/simple; bh=NKc0SY3T4jIAU97bw0efLd0WnsVUB1R7Af5NQoJf/Gc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=hBGwJjIcES++ghOv8luvdF5L/Z5h0H7JBQ2Ut4hlP4FIAGZ88NEwDpMdmpshvpMwRxtuJI4Jf8Ln7ro6SsdJbR4cCKrFPCV9fGYFUqKNkNF24rvH4/bxUuaFk2YrcPfXrZqoOgZKBxg/BhPBl+RXDyJDHR23zQ0cJFr+d2bvVlw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=gKY23PNS; 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="gKY23PNS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 821C7C4CEEF; Wed, 25 Jun 2025 14:42:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1750862543; bh=NKc0SY3T4jIAU97bw0efLd0WnsVUB1R7Af5NQoJf/Gc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=gKY23PNSCm+VJuzMvl1eEFd1tUm9T47R4cy5e9m/rHDDUpRCLgyz5tW4eg0yDOtjT J/FLk/qCMMRfIcKT/UOAR/VqXgA7j2NW5GCSE4w3/4uiTZTz5nkNScffQXl6h8vSFr t/s9Bt5MBxKNnkNCU+PuYKiI29erg2I4HMS+FhRXNIt0lHMzKfXbP8WFQ9nfmAakrf AC5t34SjqyO7nINg8LMYXNoTxCdPnb7ORQVcgA/oG/w7wCcfchMYVyOE5+d5Waah7x +TKDfUBZ9ewuAicZaYy5DXbNLu74bKCj1Mjnu2HDZOpAdyI8SwdYa16Qk8F4NMQU0V 9LPXf/ScILvNg== Date: Wed, 25 Jun 2025 16:42:21 +0200 From: Frederic Weisbecker To: Gabriele Monaco Cc: Thomas Gleixner , linux-kernel@vger.kernel.org, Anna-Maria Behnsen , Waiman Long Subject: Re: [PATCH v6 6/6] timers: Exclude isolated cpus from timer migation Message-ID: References: <20250530142031.215594-1-gmonaco@redhat.com> <20250530142031.215594-7-gmonaco@redhat.com> <875xgqqrel.ffs@tglx> <878qlhnunz.ffs@tglx> <1bc41a7a5bd46860318b0417fa27121758f28448.camel@redhat.com> <87a55waylv.ffs@tglx> <7955e52177e1ad9c309df9e6f788103ae46541cf.camel@redhat.com> 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: <7955e52177e1ad9c309df9e6f788103ae46541cf.camel@redhat.com> Le Wed, Jun 25, 2025 at 03:46:02PM +0200, Gabriele Monaco a écrit : > Thanks both for the reviews. > I'm a bit puzzled by what is expected now, though. > > The late initcall would work just fine to replace the call to > tick_nohz_cpu_hotpluggable(), indeed superfluous for hotplug calls, > however the checks for housekeeping CPUs is required to prevent > isolated CPUs getting online from becoming available and so will run on > early boot too (without any practical reason, only because the hotplug > handlers run there). > > I might avoid it by playing with cpuhp_setup_state_nocalls perhaps, but > that feels even more hacky. > > Otherwise, I can refactor the code to maintain a separate field > (isolated), restore the 'online' field and keep the functions for > online/offline and isolation as separate as possible, while considering > available = !isolated && online > > This would make reading housekeeping masks superfluous on hotplug (and > boot) code, but again, it doesn't look simpler to me. > > Am I missing some obviously elegant solution here? I keep being confused as well but yes, I think you're right, we need to keep the checks anyway on CPU up. > > Thanks, > Gabriele > -- Frederic Weisbecker SUSE Labs