From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 93C2152BE5C for ; Thu, 15 Oct 2026 13:34:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792071271; cv=none; b=qLBIu47B2L4E0fPgceakJmUudXD9B2jOw4kqEmD2Psk8/+ZEkeZ459vG4kskvh7AxRjfrXWBdt+VkXNykou/yJuREr4pdRehJsuG7uc79z5KKc95jpr8p9IZX5CkiS1781ZLEVk5zM8SMarMt3oocQXtQ5KhcEIzoYPMPz1NbKA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792071271; c=relaxed/simple; bh=C6xl6GukQZKBV4KKbyx4hKZURr8yII/oPre5hMdsWso=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=p3dOTN/HlNbRFaZduj62IY/ZUg2mBQMTJyqn+NBPXcqwxGvcwEi9U5KE51ubpmpnsLRgHpcuqsfHDz8lWma1FZxBHkw6syuREVYDajP6NYmYVxgfaJirkvbZUFb0oTvZ5BQw0UGoj5bB5Snim5nj+lPr8QDVl5WOE3FBZuODjbY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fSk4s2Ne; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="fSk4s2Ne" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E1CF81F000C4; Thu, 15 Oct 2026 13:34:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792071270; bh=u6re1XmJtjSrk7I/99qHfd+Zwb9+nsUu4xAqGghABFk=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=fSk4s2NeHA+g0oR19kZvsxPM9GDmzu1yP64wQiWAXVH/DvZ/oKchSJkwXCiMyRqae zhENVvDQDw3VSsN7Ft9LIi8fsV3LEP7jFRTkYClm3Rwhc9kUo+UVNy6cEesiR0ZCi5 84vp5XGFqDm2mxzASna1EwvRGvxg7HIEj3wdsBy7eYvjfsRTbsWNZ5/kvDlexCG0HS Alz0s5uuJ4k1BF10GhGECt5zS7vQ29ie9oShX+xDoNOROdv/O1FpY9d0+oZyQ6nc4H KsrpxDHFfvA3v/yjw8Ta+4EgKYS1SLRHsvSW9dqojnlRStTzuARgMKLubg7kVeIVev bjRSsbJKaS3sw== Date: Thu, 15 Oct 2026 08:34:28 -0500 From: Clark Williams To: Sebastian Andrzej Siewior Cc: wen.yang@linux.dev, Steven Rostedt , Eric Dumazet , Jesper Dangaard Brouer , Jakub Kicinski , Paolo Abeni , linux-rt-devel@list.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v6.1-rt 00/15] net: Backport backlog-NAPI threads to resolve PREEMPT_RT softirq warning in SMP flush Message-ID: References: <20261014150853.f8I2fNx0@linutronix.de> 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=us-ascii Content-Disposition: inline In-Reply-To: <20261014150853.f8I2fNx0@linutronix.de> On Wed, Oct 14, 2026 at 05:08:53PM +0200, Sebastian Andrzej Siewior wrote: > Please keep the networking folks out of the loop. This is a backport > request which goes entirely via the RT-queue. > > On 2026-10-14 01:58:34 [+0800], wen.yang@linux.dev wrote: > > From: Wen Yang > > > > *** Overview *** > > Backport the backlog-NAPI smpboot-thread mechanism and its prerequisite > > NAPI/RPS/defer_list work from upstream (v6.4 - v6.9) to v6.1-rt-next. > > > > *** Problem *** > > On PREEMPT_RT, RPS steers packets to a remote CPU's backlog by sending an > > IPI. The IPI handler (rps_trigger_softirq) calls ____napi_schedule(), which > > raises NET_RX_SOFTIRQ. do_softirq_post_smp_call_flush() then sees a softirq > > pending that was not pending before the flush, and NET_RX_SOFTIRQ is not > > masked by SCHED_SOFTIRQ_MASK, so it fires: > > I was about to point out that v6.1-RT should have duct tape for this but > from reading 1/15 is see that this duct is not complete and is missing > RPS. Indeed. > > A backport of what is merged is my preference, too. However, we should > get v6.6-rt fixed first then v6.1-rt. Otherwise users upgrading from > v6.1 to v6.6 will have this case broken. > > Clark, any objections here from your side? > > Sebastian I don't have a fundamental objection to the backport and agree we should do v6.6-rt first, then move that back to v6.1-rt. So it sounds like we need to pull in the RPS code first? Clark -- The United States Coast Guard Ruining Natural Selection since 1790