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=-16.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 929BFC433E2 for ; Wed, 31 Mar 2021 08:07:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 57D10619E0 for ; Wed, 31 Mar 2021 08:07:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234089AbhCaIGv (ORCPT ); Wed, 31 Mar 2021 04:06:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47378 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234098AbhCaIGZ (ORCPT ); Wed, 31 Mar 2021 04:06:25 -0400 Received: from mail-pl1-x629.google.com (mail-pl1-x629.google.com [IPv6:2607:f8b0:4864:20::629]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 59583C061760 for ; Wed, 31 Mar 2021 01:06:25 -0700 (PDT) Received: by mail-pl1-x629.google.com with SMTP id e14so7495552plj.2 for ; Wed, 31 Mar 2021 01:06:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=b7apvPbQfTG1FYg2uNsocmvMG/QdC7c4RuzNmrGKxtc=; b=A3wAmnxCijyv4JmqyD+7kgtLs8qirdeNzXs9OkQLZgeSTN5oUQUq0roBMJbBPxt+/9 KCpvVlFgxw9ZZn26eKmnOXdTk/yUg65g4D7FuF+OkmhsVMHtXbzEo9csOzlt61WDfo5l otQaPwZTrHtFhq2LaSUvhBbnk3a4qdoG8SzepxCM1HjSG+y4FAJrbwjVnc8KQwZGJR1e CfGVzDy1y8PTrPtOC8GzgLs4uQqr400S/WFl8PXrgHskVyafDc7WUeOP2bcK8aupMQhG i7D6kXW2EKvhLjAVavOvYtm/r8NX8BoRCI40+VVdhnIMvk6XnOHXiH9lgCy/TfikG8TD wozA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=b7apvPbQfTG1FYg2uNsocmvMG/QdC7c4RuzNmrGKxtc=; b=ZMyUXMPt3xX1hZurpl2MylxlEFTwUqTU4prsMC/0d1Kwt1Ws9J/1SgNkay0IxYeLQV tKJMd+c5QKySxrWP2DC8mvfyfxiQKPkstFQA0LXibqdVd8l/ruupp8QsQZUns+fyhP4r Fo1tU3IKLIp98nQkpc5938A2/zcliRuVorx8usUW2kB8ZTQ/OgAbFvapMR7WJhxqDj6G E59SwSBAWBixx8ldWppaVW12ZDW7aCW1Gx+To2/0DuxfELddYB5PwzxXaqJMXWLblnGA fe7XYgv8B0iSWW5iil3DKgpX+/ks69o5zMnSTIEfrxsj48eQH92TnAdwWejl3ZJZ2DQX hj3A== X-Gm-Message-State: AOAM530G3c3/lJ/cXch8ANdOs6wjJ1CrEoOIJRw2Wn4ad2O/PEyY4/uz RD7UH4731LGPzLIri2kyocCT X-Google-Smtp-Source: ABdhPJxHUvXwhgpDdQBLTdQxkUD9V2flhkuKgUAC1U22SyapfEwojQlQDvAYR/WYJKJ9peQYTPOWLw== X-Received: by 2002:a17:902:7b82:b029:e7:32bc:92 with SMTP id w2-20020a1709027b82b02900e732bc0092mr1917558pll.34.1617177984900; Wed, 31 Mar 2021 01:06:24 -0700 (PDT) Received: from localhost ([139.177.225.243]) by smtp.gmail.com with ESMTPSA id p2sm1643371pgm.24.2021.03.31.01.06.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 31 Mar 2021 01:06:24 -0700 (PDT) From: Xie Yongji To: mst@redhat.com, jasowang@redhat.com, stefanha@redhat.com, sgarzare@redhat.com, parav@nvidia.com, hch@infradead.org, christian.brauner@canonical.com, rdunlap@infradead.org, willy@infradead.org, viro@zeniv.linux.org.uk, axboe@kernel.dk, bcrl@kvack.org, corbet@lwn.net, mika.penttila@nextfour.com, dan.carpenter@oracle.com Cc: virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, kvm@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [PATCH v6 02/10] eventfd: Increase the recursion depth of eventfd_signal() Date: Wed, 31 Mar 2021 16:05:11 +0800 Message-Id: <20210331080519.172-3-xieyongji@bytedance.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210331080519.172-1-xieyongji@bytedance.com> References: <20210331080519.172-1-xieyongji@bytedance.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Increase the recursion depth of eventfd_signal() to 1. This is the maximum recursion depth we have found so far, which can be triggered with the following call chain: kvm_io_bus_write [kvm] --> ioeventfd_write [kvm] --> eventfd_signal [eventfd] --> vhost_poll_wakeup [vhost] --> vduse_vdpa_kick_vq [vduse] --> eventfd_signal [eventfd] Signed-off-by: Xie Yongji Acked-by: Jason Wang --- fs/eventfd.c | 2 +- include/linux/eventfd.h | 5 ++++- 2 files changed, 5 insertions(+), 2 deletions(-) diff --git a/fs/eventfd.c b/fs/eventfd.c index e265b6dd4f34..cc7cd1dbedd3 100644 --- a/fs/eventfd.c +++ b/fs/eventfd.c @@ -71,7 +71,7 @@ __u64 eventfd_signal(struct eventfd_ctx *ctx, __u64 n) * it returns true, the eventfd_signal() call should be deferred to a * safe context. */ - if (WARN_ON_ONCE(this_cpu_read(eventfd_wake_count))) + if (WARN_ON_ONCE(this_cpu_read(eventfd_wake_count) > EFD_WAKE_DEPTH)) return 0; spin_lock_irqsave(&ctx->wqh.lock, flags); diff --git a/include/linux/eventfd.h b/include/linux/eventfd.h index fa0a524baed0..886d99cd38ef 100644 --- a/include/linux/eventfd.h +++ b/include/linux/eventfd.h @@ -29,6 +29,9 @@ #define EFD_SHARED_FCNTL_FLAGS (O_CLOEXEC | O_NONBLOCK) #define EFD_FLAGS_SET (EFD_SHARED_FCNTL_FLAGS | EFD_SEMAPHORE) +/* Maximum recursion depth */ +#define EFD_WAKE_DEPTH 1 + struct eventfd_ctx; struct file; @@ -47,7 +50,7 @@ DECLARE_PER_CPU(int, eventfd_wake_count); static inline bool eventfd_signal_count(void) { - return this_cpu_read(eventfd_wake_count); + return this_cpu_read(eventfd_wake_count) > EFD_WAKE_DEPTH; } #else /* CONFIG_EVENTFD */ -- 2.11.0