From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D0F24C433E0 for ; Wed, 3 Mar 2021 14:40:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8C55E64EE1 for ; Wed, 3 Mar 2021 14:40:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1383348AbhCCOjC (ORCPT ); Wed, 3 Mar 2021 09:39:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37974 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1843000AbhCCKXf (ORCPT ); Wed, 3 Mar 2021 05:23:35 -0500 Received: from mail-qt1-x836.google.com (mail-qt1-x836.google.com [IPv6:2607:f8b0:4864:20::836]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6ACC7C0698C7 for ; Wed, 3 Mar 2021 01:07:03 -0800 (PST) Received: by mail-qt1-x836.google.com with SMTP id d11so16240185qtx.9 for ; Wed, 03 Mar 2021 01:07:03 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=xKpRIV0nBsirWLUBi5T/YqLwJUbvRGd0l5J76HxqqQY=; b=i93FVC4prisYD3tUaa4qTULSzppFJdnwqaI0axKLqk4E1KHLGl0ajxMpSx/Tbcz5gz cB+p+QCfBLFfjgNlV1gpaGUgstlS9F/9xajs3I7SB+BpptWiAPSxxY5Bf/9oiNmWwWx5 iImSH5q2b+x5PftlRI6vcph/A+eUGLveFSsOVWgp6xIAet72Oo3bSy6BHl1JZiHZjGi9 uvz9PBafoUuLvJ9kZdOPmWYbpzXTTt39rbO+031348ZQbxY6CD3J/+YmoQT3dJ1awTCf 8S3Tyc99ojTXxhyesNABrGX29I/Qyj0IqyrgPWjyPtXROEULfbOANHQPoiJ3gh8xbsWJ VO3A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=xKpRIV0nBsirWLUBi5T/YqLwJUbvRGd0l5J76HxqqQY=; b=eW42jnpasXk8A+Y8wj1QxifRPpV7TXbCuGYr5sK4kuC+LNnl1GGkreewggstvww7Rt Sp3yWNGfkCgNcL0HasMcy2FXWDQg/XYE1rxRrEuyEFm82nZnR/rPr1KzRITB2wEVR4Bi mz89yxCkn+byAqiyc8CD7Y9t60bJ7F7qSY8QlUGcctHWunS+RERTgv1julYHA5PebZLW 63XmIfoUNQvCiOHzcRUi/iH/3rg0+ltkPmV84WYVr8ETlRwhiUa9/NkWQGEXZDi4ROHe uFdlFR4+v3pvpwK+4RzmpwVvvlVjkBgpnfbXQTeOq2Z5vtnPUu3lgZ1tNzruB307PQww ZeAg== X-Gm-Message-State: AOAM5301P9TTRKimUE4fOCaaQhjlJY5CY7sUrxaMZ/0vetLX2bjO769d mV5bWNWV2Xf5CsCQbbfB5EyjtQSKJqWfk/NirYIt/w== X-Google-Smtp-Source: ABdhPJx8+N6LxjQ2TqesKmjDhe9IP8WsEr+KW8d/OM0/MKlgrV9PLrRVbVZT/kcWCKVmkhK0QwJAnR1Edcir13+sqW8= X-Received: by 2002:ac8:6f3b:: with SMTP id i27mr10377291qtv.67.1614762422440; Wed, 03 Mar 2021 01:07:02 -0800 (PST) MIME-Version: 1.0 References: <00000000000039404305bc049fa5@google.com> <20210224023026.3001-1-hdanton@sina.com> <0a0573f07a7e1468f83d52afcf8f5ba356725740.camel@sipsolutions.net> <20210303085912.1647-1-hdanton@sina.com> In-Reply-To: <20210303085912.1647-1-hdanton@sina.com> From: Dmitry Vyukov Date: Wed, 3 Mar 2021 10:06:51 +0100 Message-ID: Subject: Re: BUG: soft lockup in ieee80211_tasklet_handler To: Hillf Danton Cc: Johannes Berg , syzbot , LKML , linux-wireless , syzkaller-bugs Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 3, 2021 at 9:59 AM Hillf Danton wrote: > > On Tue, 02 Mar 2021 15:18:16 +0100 Johannes Berg wrote: > > On Wed, 2021-02-24 at 10:30 +0800, Hillf Danton wrote: > > > > > > Add budget for the 80211 softint handler - it's feasible not to try to > > > build the giant pyramid in a week. > > > > > > --- x/net/mac80211/main.c > > > +++ y/net/mac80211/main.c > > > @@ -224,9 +224,15 @@ static void ieee80211_tasklet_handler(un > > > { > > > struct ieee80211_local *local = (struct ieee80211_local *) data; > > > struct sk_buff *skb; > > > + int i = 0; > > > + > > > + while (i++ < 64) { > > > + skb = skb_dequeue(&local->skb_queue); > > > + if (!skb) > > > + skb = skb_dequeue(&local->skb_queue_unreliable); > > > + if (!skb) > > > + return; > > > > I guess that's not such a bad idea, but I do wonder how we get here, > > userspace can submit packets faster than we can process? > > I wonder why syzbot did not make other handlers stand out than > ieee80211_tasklet_handler. syzbot has no relation to this whatsoever. It's just a proxy between the kernel and you. Ask the kernel ;) > > It feels like a simulation-only case, tbh, since over the air you have > > limits how much bandwidth you can get ... unless you have a very slow > > CPU? > > Even with a slower CPU I want to run a FIFO task every tick - it can bear > latencies like two seconds. > > > > In any case, if you want anything merged you're going to have to submit > > a proper patch with a real commit message and Signed-off-by, etc. > > > > johannes