From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 64D5454CF6D for ; Wed, 14 Oct 2026 15:08:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791990540; cv=none; b=r8BTttWjD9YFkq521peuoYcsVEe5RjBkQ437uxU+VoUwVzxoDL4Ev2LT/SOJf4VJND9urd2Tbqsgx7L2NckQQT9Kz2rgoztNDez5yKmHbCFEthcX6ZWT2ujSIOO3gKP4vkIhWg6J9uRB4a+kqkYlH+cM+VMXDpMA0xsi4463O60= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791990540; c=relaxed/simple; bh=kmmF0P+i5UWKRlZ9F/TFFB8xOojGwHSnZNx1VhtwHr0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ZAA+W3ViEkVZz5Nxt1sisVDW8HPvn0mF5UH8dAXC8Tqux8DCwidiEmlW7WSsJQLl6bSqA+a/cYIi6GGkxUeqpdVrk+kj2JOgZ6gcygxXBZMehPk2rcsTN6ukFazSVUPkB7OB0FIMuCt5t+7BS7sSMx0UFMWQWZinbpgV2GvZco8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=mLALfMK7; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=1LuPuFtT; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="mLALfMK7"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="1LuPuFtT" Date: Wed, 14 Oct 2026 17:08:53 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1791990534; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Cw3APKaQu/b4+Iid0imheNzIZFinTC6z+bGAfQ94t3c=; b=mLALfMK7Fzggs3t0AYQpg1ocwxErtF3Dr8xq+hJofeWD9RVMwtKCOs0SY1M9cMgXQJlqSC TIKwoE8g17gw955ZBlCDQuchBIn+jWiI2peyb0uiatXweCXChKMjqkdH1Yk6YrEgbO9Zpn rUXcVDo87Vfc9R6q7+QZ1P1alCPbJtdYww1w8YOmOJcj8sq6Ok9yOs1aXm01EiXrOvTwT0 erCgSwMGGjJOsrmjxoVRYdJYW2OqGgISxFedpNhEmP4q039FEQYVcj/HWiQv642DN//Z1q foFO0iU7nveiWMlzyCv80zsntJ5esd+HdanJWFR4AnQed3oAnXGvEO2QnXehCQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1791990534; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Cw3APKaQu/b4+Iid0imheNzIZFinTC6z+bGAfQ94t3c=; b=1LuPuFtTe9YHcRgJP8AVdTyePRRJeJg89Mip3HrncKEC1iU7nOXq8KDOc90t7dARB7TPrR QY4qcdQOTbM/aEDQ== From: Sebastian Andrzej Siewior To: wen.yang@linux.dev, Clark Williams Cc: 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: <20261014150853.f8I2fNx0@linutronix.de> References: 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=utf-8 Content-Disposition: inline In-Reply-To: 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