From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=95.215.58.230 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792430297; b=XbHladRgJWOPCTCoTIScL5N8hOWOvm/DwlKbT9IekHU/c5k+x1zP55XJqnBpu2SAihLt v1pUhx6XQX2721fl9BCAI5s6pFTqWbHH0lyRaa6djHcX+JuaoXH+yZKri1TQBGHAguEg+ L1s86OVZXpspHuyRNPwjXpnpFnzlQzJ+vjGc12L2uz/vFcU8F12FG/k8v6OIcgtoBd+mT ktfAmvBMoGVDN1/dyUSkKfPF1ki3T0hKRD2uqr1Lvy87/ieVQnamL+49ROaBOs0ne1pP5 HP0vfdmle1aNeM+VkAp5j4bgn0gu+RxjOqqPB/uLzzHaco03u6CyDRvNE3O6YQWGk7w== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792430297; h=DMARC-Filter:X-Envelope-To:DKIM-Signature:X-Envelope-To:Received: X-Mizu-Trace-ID:X-Migadu-Flow:Message-ID:Date:MIME-Version:User-Agent: Subject:To:Cc:References:Content-Language:From:In-Reply-To: Content-Type:Content-Transfer-Encoding; bh=1QVI3QjKpq5IRp/fPAlVbiDEQ4TylZ7mMiLxWJOvw/Y=; b=LQSKZGYipB2PvKlF8Xt6Zxx98Bq/RubCulxh7hHjuT+4yJ28h0A0YdVqZ6hkTC4s1WST IxNJ04ZCWyXuLzaIThj33XSDYjPx6XFN5p4y83eTXOX0gRXERdkbONVnZuXq9Mim9Zc7o KHxw2MBXbeVsItQAdhapYnWxYJwb8SO77EryvLmFn/61/Z2hfLO99abq7TR2ONeDbr0Lw tNsnVW7LqV0dNXB4R1U2kmY3D7U3AHQwDgxQbT3GpIdvUaeAA9zbTHal736bmHobfNGB5 8pQpqSOPZeIr/BDF3fNcn9SlPlsQMmY+jdCzY4bmi8AIJTlJps51tRoKGtiNQ/Hyxbw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=oYK0AIy4; arc=none smtp.remote-ip=95.215.58.230 Received: from mta1.migadu.com (out-230.mta1.migadu.com [95.215.58.230]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B1EB9606A319 for ; Mon, 19 Oct 2026 17:18:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org B1EB9606A319 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=oYK0AIy4 X-Envelope-To: linux-rt-devel@lists.linux.dev DKIM-Signature: a=rsa-sha256; bh=q9xa9YZjnuyg7a1fSJv/UTzPcIbUjacY94dKtBXHcyA=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1792430294; v=1; x=1793035094; b=oYK0AIy4FVdhDfDyLu+EAQr2Qlefwc1wZxgktxcdwV/RuP8/peuTPUEu0kk+gN57QOyi0pEG LdVvOoQOeFu+Hdx63qMVqQxTXiid4cZJ+hbZJB7GE3EcV1OO0i3qo9qiODKlUHESbm8UDlw82Wj 9xjkGiFLUr21mDG7rZ+d3SdM= X-Envelope-To: linux-rt-devel@lists.linux.dev Received: by smtp.migadu.com with ESMTPS id 2f87e9bf7523bc8a; Mon, 19 Oct 2026 17:18:14 +0000 X-Mizu-Trace-ID: 2f87e9bf7523bc8a X-Migadu-Flow: FLOW_OUT Message-ID: Date: Tue, 20 Oct 2026 01:18:06 +0800 X-Mailing-List: linux-rt-devel@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 6.6-rt 0/5] net: Backport backlog-NAPI threads to resolve PREEMPT_RT softirq warning in SMP flush To: Clark Williams Cc: Sebastian Andrzej Siewior , Steven Rostedt , linux-rt-devel@lists.linux.dev References: Content-Language: en-US From: Wen Yang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 10/19/26 21:20, Clark Williams wrote: > On Mon, Oct 19, 2026 at 02:15:22AM +0800, wen.yang@linux.dev wrote: >> From: Wen Yang >> >> Backport backlog-NAPI threads to v6.6-rt-next first, as requested by >> Sebastian and Clark, before following up with the v6.1-rt backport. >> The base is 4c4970859022 (Linux 6.6.151-rt78-rc1). >> >> The existing RT workaround, 1f7514c9c75d ("net: Avoid the IPI to free the"), >> redirects deferred skb cleanup to a worker but leaves RPS remote-backlog >> scheduling on the function-call IPI path. In a fresh RT guest this still >> triggers do_softirq_post_smp_call_flush() from idle queue flushing. >> >> The ten earlier NAPI/RPS prerequisites are already present in v6.6, so this >> series reverts the workaround and backports the four upstream changes (all >> in upstream v6.10) in dependency order. Backlog-NAPI threads replace the >> RPS/defer function-call notifications; ordinary scheduler wakeup IPI traffic >> can still occur. Two of the changes were previously backported to ordinary >> 6.6.y and reverted (507692c05636, 5a530c8ead06) only because PREEMPT_RT is >> absent there, not for a functional defect. >> >> Backport notes >> -------------- >> Only 3/5 needs context adaptations; they are listed in that patch's commit >> message. The other four apply without context edits. Unlike v6.1, v6.6 keeps >> WRITE_ONCE(napi->list_owner, ...) because the field already exists here. >> >> Verification >> ------------ >> Each of the five stages was replayed against the base snapshot and compiled >> for net/core/dev.o and net/core/skbuff.o. The baseline and final RT/RPS >> bzImages were built with byte-identical normalized configs using GCC 9.4.0, >> with no compiler warnings or errors. >> >> Tests use virtme-ng 1.38, x86_64 QEMU/KVM, four vCPUs and 2 GiB memory: >> >> vng --run --cpus 4 --memory 2G \ >> --qemu-opts='-machine accel=kvm' --exec 'bash