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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2C43BC4332F for ; Fri, 2 Dec 2022 18:29:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234488AbiLBS3G (ORCPT ); Fri, 2 Dec 2022 13:29:06 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59238 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234487AbiLBS2j (ORCPT ); Fri, 2 Dec 2022 13:28:39 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 379655FC8 for ; Fri, 2 Dec 2022 10:27:43 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1670005662; 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=54ctooy2QqFYuJAUYh1DElEphCo1HVKkIgS8Rlu6y1s=; b=STT/hajNgav/BmVQD2sRJ+7IG2T95inCcYl5wbLZz18p+MZMOl7dsxDB/8PEt7b+sslUHM RyLZFW+TffKiX3f1BDJ+6xmw0werntPw08OarPQG+IKlvElCdYVUMY9ewDo9+ZMWH1grKo Dj65x47RHxcgzqJcdQqhZR7pS2GOCfE= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-60-g37Wa3yoPp2jHJ8ayrtkFQ-1; Fri, 02 Dec 2022 13:27:41 -0500 X-MC-Unique: g37Wa3yoPp2jHJ8ayrtkFQ-1 Received: by mail-wm1-f69.google.com with SMTP id 6-20020a1c0206000000b003d082ecf13cso1521576wmc.3 for ; Fri, 02 Dec 2022 10:27:41 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=54ctooy2QqFYuJAUYh1DElEphCo1HVKkIgS8Rlu6y1s=; b=cS20jnEFeJ4aEYOCf63+3yeazZJFiLezoOkHUZjOMTJ+tjeNDVWXb0W08/tL66itY7 HqW4Qm5qRz9bj7Ibht6VhpGzzqX2/CXWHvYpqxy2Ll6/I26lIw/5uMeglqcgB5CAChgM Wez36ETiGb/SoI9j6Pk16E6knMVsNiu3SVCNnRjzELQ4O814N409ZWaD8G/NiOPmxdlE 0w+G+1JD6zGLHJT2OoxO7W4NXij+GQi+2vDPC30pODxOY74w764gd2dBb883vcXQ0wHw XIid2fzh7VlOsevrXgIqUDFB2FEGjW944U7FgeRiCygzrTuoAcgugd0d/o2hZm5F7Mql 4/Cg== X-Gm-Message-State: ANoB5pmPV+oLKQM7El6223r+RxJBNIpOk1BVxImmGLEehEgBz9LW1SDM S9pL96as8jtvyf6Upa09XvIBfbO+Ek3M0J2Y+lbU10HThj3hRgoW97SSZrJ6A7ljgg8f52OgP9U QBRDEM5fFY73WUmqhx+AGIO8V X-Received: by 2002:a5d:4247:0:b0:241:a82b:5dee with SMTP id s7-20020a5d4247000000b00241a82b5deemr33101734wrr.425.1670005660258; Fri, 02 Dec 2022 10:27:40 -0800 (PST) X-Google-Smtp-Source: AA0mqf4bv7vlxU81ieqvd+1vTTRoDR95EdMlYVUn4OoUKLb4/+a4NyF4K4UfXapKxpaQkNnmTY+sig== X-Received: by 2002:a5d:4247:0:b0:241:a82b:5dee with SMTP id s7-20020a5d4247000000b00241a82b5deemr33101729wrr.425.1670005660048; Fri, 02 Dec 2022 10:27:40 -0800 (PST) Received: from ?IPV6:2001:b07:6468:f312:9af8:e5f5:7516:fa89? ([2001:b07:6468:f312:9af8:e5f5:7516:fa89]) by smtp.googlemail.com with ESMTPSA id h17-20020a05600c315100b003cfd64b6be1sm17954901wmo.27.2022.12.02.10.27.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 02 Dec 2022 10:27:39 -0800 (PST) Message-ID: <4405c412-f9df-ed43-8050-4d4a90d5dcc5@redhat.com> Date: Fri, 2 Dec 2022 19:27:38 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.5.0 Subject: Re: [PATCH] KVM: Deal with nested sleeps in kvm_vcpu_block() Content-Language: en-US To: Space Meyer Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, kpsingh@kernel.org References: <20221130161946.3254953-1-spm@google.com> From: Paolo Bonzini In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/2/22 16:52, Space Meyer wrote: >> Also, this does not work I think, because there is >> add_wait_queue()/remove_wait_queue() pair. Adding it is not easy >> because KVM is using a struct rcuwait here instead of a wait_queue_t. > Ah, sorry. I really was a bit quick on this one. I agree nothing would ever call > woken_wake_function, hence my patch doesn't make sense. Looking at the rcuwait > code I don't see something similar to wait_woken. > > Do you see some other way we could avoid the pattern susceptible to the nested > sleeping problem? No, I think we should just treat them as bugs and fix them. Paolo