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=-6.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, USER_AGENT_SANE_1 autolearn=no 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 ED7DAC433F5 for ; Tue, 14 Sep 2021 10:11:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CF68A610A6 for ; Tue, 14 Sep 2021 10:11:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231464AbhINKMZ (ORCPT ); Tue, 14 Sep 2021 06:12:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34016 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229969AbhINKMX (ORCPT ); Tue, 14 Sep 2021 06:12:23 -0400 Received: from mail-pf1-x42e.google.com (mail-pf1-x42e.google.com [IPv6:2607:f8b0:4864:20::42e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 61195C061574 for ; Tue, 14 Sep 2021 03:11:04 -0700 (PDT) Received: by mail-pf1-x42e.google.com with SMTP id 18so11678202pfh.9 for ; Tue, 14 Sep 2021 03:11:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-transfer-encoding:content-language; bh=v+HvihQ88+3rcrBO8y3dqOMl+9UvluYXt6seefmUvYA=; b=RjQsLf+0TEnI9r2RX1x0HCA8NKb87k4SaGuuP3EqDGJggSvrCbKas5yRUoEHWo4KpI fmBAQOJNht4PKXoTqiok9yU9P1gGgaRN4toMjTKNkI/bHrqZIIHe1LQdoZtu5UaGLjD7 1aRV9DkhMZERHqECNki1jZl0uT4fLY+pmOQYuVYQZJJacEjleCklPy5ObJtYIKtWfI1u BTlLE9SzPI+4QEq3/jX/fZ9N47sFlZaZJkfn2a3dqqZftbCgzyIvErLomvHALh1ylNU/ BpXOSFLlOmVZz+U4Wh4qoFEVA/4eA7p4LsJ4sR1NnMAKS7PmmwpIn4lY23Yupka21S1k 1Plw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :content-language; bh=v+HvihQ88+3rcrBO8y3dqOMl+9UvluYXt6seefmUvYA=; b=uHHb5KYc3Wyjqsmbq6GKJ/2UJfWR434mz8TISxH+LBHD7j+8V66wDzIm0+C+WSZWj3 Tv1niXDQT7L+o4WcSz9AeeIqPmQYHpkKkYdKqfgDmMAC9aWqgFXIG1wGI1PzIdvlgzXS QbA3x1Wmwf2pmEZxEl2bn9P699N4YQxrFzbkDhrodKmDb/dfginTt1ovyqc3YTYJgey7 9Qn2ZMTc4vZXmcncYwFqiFlW/EkJOKHnYsHJYrCctLwqpJqtWvqKXmYDUEfhwYZJ7hTz GBsorpZJREEYJlefUwth1YbZrEhBbIk3RvMuxC3scP+ap3+R8OVYFsl0K7+LXhSNDxwd yvsQ== X-Gm-Message-State: AOAM533Pdb+D0f+TKxGjrMs/n214MpSPo1wxD/usk7qFCa0JTf26XNq9 n+NE0NzYhRWDmnabP0T4XM8WQPj2BNk= X-Google-Smtp-Source: ABdhPJzavhsobzYlsMLGf676R+ltWlrPwA3WT7aJpIVN07+WHfesgcCuVQukRiO8xyOOdsRYHa30Qw== X-Received: by 2002:aa7:8014:0:b029:3cd:b6f3:5dd6 with SMTP id j20-20020aa780140000b02903cdb6f35dd6mr4042791pfi.39.1631614263608; Tue, 14 Sep 2021 03:11:03 -0700 (PDT) Received: from [10.102.0.6] ([85.203.23.52]) by smtp.gmail.com with ESMTPSA id s26sm9668465pfw.5.2021.09.14.03.11.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 14 Sep 2021 03:11:03 -0700 (PDT) Subject: Re: [BUG] android: possible ABBA deadlock in print_binder_proc() and binder_get_txn_from_and_acq_inner() To: Todd Kjos Cc: Greg KH , arve@android.com, tkjos@android.com, maco@android.com, joel@joelfernandes.org, christian@brauner.io, hridya@google.com, surenb@google.com, linux-kernel References: <303401d0-25c9-d04b-e96d-3ca2aa0a616d@gmail.com> From: Jia-Ju Bai Message-ID: <37c6a84a-77ee-449b-a83b-59e378242fcb@gmail.com> Date: Tue, 14 Sep 2021 18:10:59 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Thanks for the reply :) On 2021/9/8 3:29, Todd Kjos wrote: > On Mon, Sep 6, 2021 at 7:30 PM Jia-Ju Bai wrote: >> Hello, >> >> My static analysis tool reports a possible ABBA deadlock in the android >> driver in Linux 5.10: >> >> print_binder_proc() >> binder_inner_proc_lock() >> _binder_inner_proc_lock() >> spin_lock(&proc->inner_lock); --> Line 662 (Lock A) >> print_binder_thread_ilocked() >> print_binder_transaction_ilocked() >> spin_lock(&t->lock); --> Line 5531 (Lock B) >> >> binder_get_txn_from_and_acq_inner() >> binder_get_txn_from() >> spin_lock(&t->lock); --> Line 1833 (Lock B) >> binder_inner_proc_lock() >> _binder_inner_proc_lock() >> spin_lock(&proc->inner_lock); --> Line 662 (Lock A) > Hmm. What kernel version are you looking at? These line numbers don't > match what I see in mainline. Linux 5.10 > Also, the sequence for > binder_get_txn_from_and_acq_inner() looks like this for me: > > binder_get_txn_from_and_acq_inner() > binder_get_txn_from() > spin_lock(&t->lock); --> Line 1427 (Lock B) > spin_unlock(&t->lock); --> Line 1431 (Lock B) > binder_inner_proc_lock() > _binder_inner_proc_lock() > spin_lock(&proc->inner_lock); --> Line 256 (Lock A) > > Which doesn't have the deadlock hazard. > Yes, you are right. My static tool has several errors in the implementation, and thus reported this false positive, sorry... Best wishes, Jia-Ju Bai