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=-12.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 AD88EC433B4 for ; Thu, 29 Apr 2021 06:50:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7665961419 for ; Thu, 29 Apr 2021 06:50:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232090AbhD2GvL (ORCPT ); Thu, 29 Apr 2021 02:51:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51288 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238877AbhD2GvH (ORCPT ); Thu, 29 Apr 2021 02:51:07 -0400 Received: from mail-pf1-x431.google.com (mail-pf1-x431.google.com [IPv6:2607:f8b0:4864:20::431]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7D6A0C06138B for ; Wed, 28 Apr 2021 23:50:20 -0700 (PDT) Received: by mail-pf1-x431.google.com with SMTP id c3so26671345pfo.3 for ; Wed, 28 Apr 2021 23:50:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=8Sjs/qcN62tImx0y3y2XAUfVwF7AM9LLy6umWEbVG8w=; b=TX7c/xviVNjBLWT+DkxyQEf0lpH8+Gne8DU/X1k3TrZKR0hxNi6Q6Xn+RqV83TYI1l XPl0x78hveiDuFh4j3P9AgFtZQaz0fc0IWlXdR/Un13SvhOkx8mbSdrC1iTieLz6Dkji U06qF/V0yjF/SCRWftyXtlrZWS5RxdafvCctB9Lxmt3wuAvKG4tIRhxVH5X46eqEmeyB AWt2uS56zuXczQOoe47EEDL2OwkAW4bPJuswRQOZxmguleUtH+6oIC0zhfxbKXvqpJms EpdU9Wy7VdOJ29OoPA0JxSwxosXnc2eiHsrYwDIR2JcU5Cbm3fpM8NFSwAHfqGjvpD/O 1fEA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=8Sjs/qcN62tImx0y3y2XAUfVwF7AM9LLy6umWEbVG8w=; b=LSzNTrt7xkv/qUOsoS6l8PZmnnRLTxWem3jOGX0wtIdkO5EJNylje+4rj/ow3x1R04 bJpHhDGv9/BZf7QDu9kkOH6xDR8VjP0vBr6Z2bq+qttOHqX2Ept9e4iSQ10ubnij8DqX QL4S2vXUwtkByopv3Gbmh3jYxbUgc60i7wPqTT29lGQzHFuGDEL8o2t0xfRbsH4tvdBC nfdasMs7mXwbLLWvYpA5ACpaBYOo8TP4NlR8hhe7RWGnPAn4S50lI7pyxP/hNS2MJc66 r9MQbVN3gqmmePq+8XL2oo7jVdPE+opFO+DC4V558uQwrS1Oy40N5KJtVF19KUN/Kw3n cMTA== X-Gm-Message-State: AOAM533N3a0LOUg15CY4Gl3O1TItpA49aLupvLiHL1+xSsYjrb65VDol FFDMrb97pFDFf4VaxWBwGcU= X-Google-Smtp-Source: ABdhPJxNQVcep5m3uq9y8KxO8imsnoEkxIHzrFfr198Zz0dfHnWmIk9xOz0iJ8C4uBWGBh73TsuA1g== X-Received: by 2002:aa7:8186:0:b029:27d:edb:c65a with SMTP id g6-20020aa781860000b029027d0edbc65amr6719470pfi.68.1619679020042; Wed, 28 Apr 2021 23:50:20 -0700 (PDT) Received: from mail.google.com ([141.164.41.4]) by smtp.gmail.com with ESMTPSA id a18sm1507599pgk.66.2021.04.28.23.50.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Apr 2021 23:50:19 -0700 (PDT) Date: Thu, 29 Apr 2021 14:50:15 +0800 From: Changbin Du To: Palmer Dabbelt Cc: changbin.du@gmail.com, Paul Walmsley , aou@eecs.berkeley.edu, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] riscv: patch: remove lockdep assertion on lock text_mutex Message-ID: <20210429065015.lqdefm2sagyacmbs@mail.google.com> References: <20210417023532.354714-1-changbin.du@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 28, 2021 at 11:20:20PM -0700, Palmer Dabbelt wrote: > On Fri, 16 Apr 2021 19:35:32 PDT (-0700), changbin.du@gmail.com wrote: > > The function patch_insn_write() expects that the text_mutex is already > > held. There's a case that text_mutex is acquired by ftrace_run_update_code() > > under syscall context but then patch_insn_write() will be executed under the > > migration kthread context as we involves stop machine. So we should remove > > the assertion, or it can cause warning storm in kernel message. > > > > [ 104.641978] ------------[ cut here ]------------ > > [ 104.642327] WARNING: CPU: 0 PID: 13 at arch/riscv/kernel/patch.c:63 patch_insn_write+0x166/0x17c > > [ 104.643587] Modules linked in: > > [ 104.644691] CPU: 0 PID: 13 Comm: migration/0 Not tainted 5.12.0-rc7-00067-g9cdbf6467424 #102 > > [ 104.644907] Hardware name: riscv-virtio,qemu (DT) > > [ 104.645068] Stopper: multi_cpu_stop+0x0/0x17e <- 0x0 > > [ 104.645349] epc : patch_insn_write+0x166/0x17c > > [ 104.645467] ra : patch_insn_write+0x162/0x17c > > [ 104.645534] epc : ffffffe0000059c6 ra : ffffffe0000059c2 sp : ffffffe002a33c70 > > [ 104.645580] gp : ffffffe0019e5518 tp : ffffffe002a232c0 t0 : ffffffe01295e8a8 > > [ 104.645622] t1 : 0000000000000001 t2 : 0000000000000000 s0 : ffffffe002a33cc0 > > [ 104.645675] s1 : ffffffe000007f72 a0 : 0000000000000000 a1 : ffffffffffffffff > > [ 104.645716] a2 : 0000000000000001 a3 : 0000000000000000 a4 : 0000000000000001 > > [ 104.645757] a5 : ffffffe0799e45c8 a6 : 00000000000ca097 a7 : 0000000000000000 > > [ 104.645798] s2 : 0000000000000008 s3 : 0000000000000f72 s4 : ffffffe002a33ce0 > > [ 104.645839] s5 : 0000000000000f7a s6 : 0000000000000003 s7 : 0000000000000003 > > [ 104.645880] s8 : 0000000000000004 s9 : 0000000000000002 s10: 0000000000000000 > > [ 104.645920] s11: 0000000000000002 t3 : 0000000000000001 t4 : ffffffe000c615c8 > > [ 104.645958] t5 : 0000000000007fff t6 : 0000000000000380 > > [ 104.645998] status: 0000000000000100 badaddr: 0000000000000000 cause: 0000000000000003 > > [ 104.646081] Call Trace: > > [ 104.646147] [] patch_insn_write+0x166/0x17c > > [ 104.646280] [] patch_text_nosync+0x10/0x32 > > [ 104.646317] [] ftrace_update_ftrace_func+0x74/0xac > > [ 104.646352] [] ftrace_modify_all_code+0x9c/0x144 > > [ 104.646387] [] __ftrace_modify_code+0x12/0x1c > > [ 104.646420] [] multi_cpu_stop+0xa8/0x17e > > [ 104.646451] [] cpu_stopper_thread+0xb2/0x156 > > [ 104.646489] [] smpboot_thread_fn+0x102/0x1ea > > [ 104.646524] [] kthread+0x132/0x148 > > [ 104.646556] [] ret_from_exception+0x0/0x14 > > [ 104.646657] ---[ end trace ccf71babb9de4d5b ]--- > > [ 104.647444] ------------[ cut here ]------------ > > > > Signed-off-by: Changbin Du > > --- > > arch/riscv/kernel/patch.c | 13 ++++++------- > > 1 file changed, 6 insertions(+), 7 deletions(-) > > > > diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c > > index 0b552873a577..6d2ed9c15065 100644 > > --- a/arch/riscv/kernel/patch.c > > +++ b/arch/riscv/kernel/patch.c > > @@ -49,19 +49,18 @@ static void patch_unmap(int fixmap) > > } > > NOKPROBE_SYMBOL(patch_unmap); > > > > + > > +/* > > + * Before reaching here, it was expected to lock the text_mutex > > + * already, so we don't need to give another lock here and could > > + * ensure that it was safe between each cores. > > + */ > > static int patch_insn_write(void *addr, const void *insn, size_t len) > > { > > void *waddr = addr; > > bool across_pages = (((uintptr_t) addr & ~PAGE_MASK) + len) > PAGE_SIZE; > > int ret; > > > > - /* > > - * Before reaching here, it was expected to lock the text_mutex > > - * already, so we don't need to give another lock here and could > > - * ensure that it was safe between each cores. > > - */ > > - lockdep_assert_held(&text_mutex); > > - > > if (across_pages) > > patch_map(addr + len, FIX_TEXT_POKE1); > > Well, we definately need the lock -- otherwise concurrent callers will > install conflicting maps for FIX_TEXT_POKE*, step on each other, and install > the wrong patch. I just sent out a patch to use an explicit lock here, as > sharing text_mutex doesn't seem safe. It has already locked by text_mutex. The real problem is lockdep cannot handle this case(with stopmachine) or it is a false positive report. -- Cheers, Changbin Du