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[2620:137:e000::1:20]) by mx.google.com with ESMTP id v19-20020aa7d9d3000000b0052340f56811si2729640eds.106.2023.08.09.06.04.26; Wed, 09 Aug 2023 06:04:51 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@linutronix.de header.s=2020 header.b=QLYmo36x; dkim=neutral (no key) header.i=@linutronix.de header.s=2020e; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=linutronix.de Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232414AbjHIK43 (ORCPT + 99 others); Wed, 9 Aug 2023 06:56:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33558 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232375AbjHIK42 (ORCPT ); Wed, 9 Aug 2023 06:56:28 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 54E4B1FF6; Wed, 9 Aug 2023 03:56:27 -0700 (PDT) Date: Wed, 9 Aug 2023 12:56:23 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1691578585; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=7otBgQNwEPlGGa7A34K/b+UVvvmPFarUTBRcW4oPvA4=; b=QLYmo36x2dYs13WAINYDsixXwTkt4dYB9Z6i4Gw61GUY4iIZUapC5EDNxvM71T3xPjGLkq tG1W2JIzxJqoWl0WrPdopEQ8lSALan7+VyLBc4Fu8Oj6ChOt8SsZ04Z5s/0OzrK0TnSf9I vn3sEZ3rmSZ3IqDB5XgiD/F7xh0qDl/FpXufLyAten1m8GO6v0/xTUG5PfudBWT44/G2aV i72oAjjcw7OwUXzxXPCrSoAIziCThCd/YyejD9/vk7oezxqRyOJgTrIc+1r2wBYRa44bld hvIcw7IiCnjRS0+xRE9U8mhskhvYsgPhKsIJ8TzoKlr1HtJf30VY08Uv/1l2ZQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1691578585; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=7otBgQNwEPlGGa7A34K/b+UVvvmPFarUTBRcW4oPvA4=; b=CO/odTV2XRsNcMLrQW/O+7oYfRENV3nfWwFs96dBAyAm3shjrK083wze+INr5yXtWTZsLn HSdiYzIjnHVPDNDg== From: Sebastian Andrzej Siewior To: Wander Lairson Costa Cc: Paolo Abeni , linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org, juri.lelli@redhat.com Subject: Re: Splat in kernel RT while processing incoming network packets Message-ID: <20230809105623.DSEPQ9LC@linutronix.de> References: <20230703142908.RcxjjF_E@linutronix.de> <20230704100527.75hMNZ35@linutronix.de> <20230704144749.wJUlub6-@linutronix.de> <6cmltsaeqjcekglutpnp4lxyqnjng5m4w73ae4btwrivuxvptf@zmhahab7643i> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: <6cmltsaeqjcekglutpnp4lxyqnjng5m4w73ae4btwrivuxvptf@zmhahab7643i> X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023-07-05 12:59:28 [-0300], Wander Lairson Costa wrote: > Maybe, under RT, some softirq should run in the context of the "target" > process. For NET_RX, for example, the softirq's would run in the context > of the packet recipient process. Each task_struct would have a list of > pending softirq, which would be checked in a few points, like on scheduli= ng, > when the process enters in the kernel, softirq raise, etc. The default > target process would be ksoftirqd. Does this idea make sense? We had something similar. The softirq runs in the context of the task that raised it. So the networking driver raised NET_RX and it was processed in its context (and still is). The only difference now is that we no longer have a task based "raised bit" but a per-CPU. For RPS you already pulled the skb from the NIC, you need to process it and this isn't handled in the task's context but on a specific CPU. Let me look at per-CPU backlog thread or ripping the warning out=E2=80=A6 Sebastian