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=-19.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 C8197C43381 for ; Wed, 6 Jan 2021 01:18:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8FC4222D04 for ; Wed, 6 Jan 2021 01:18:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726718AbhAFBSm (ORCPT ); Tue, 5 Jan 2021 20:18:42 -0500 Received: from mail.kernel.org ([198.145.29.99]:60216 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726626AbhAFBSd (ORCPT ); Tue, 5 Jan 2021 20:18:33 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 55C81230FB; Wed, 6 Jan 2021 01:17:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1609895872; bh=ww/Zdig22m8u2xnm1Qhu/umiYDeAt6Ww+0ijypYNKug=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=JBVWsNytN0FF6rHC/lUNdjAHZlOC77y+9lHvsMrarARu1wpL2smnFV8zunLQqncrW 9kff/Y+JvYrQXj6cAtgmb2t0ZHOeq7vw9RK5aE4gCT0I6qSbB4jdZsm1hc84e7VbHb Fie7FblgG4V24RxRv7RI43LPYv/P5RpaErLT7iqfYjnVX7RXgig/UZiijx59R9GjhW oJNzTGOUJxvh2z8Ker9L2fJXvzaS6aymQCUExEwXXysZ0eG1jv7tIVlVRZfvkI8pIE RNkbp4NB8mIp0xIY3I0cQfHY8WEWPvM1IOraNbRxhw+Otix/qUKq1XIr+bCpO1x7N2 EJbK+bbX6fnww== From: paulmck@kernel.org To: linux-kernel@vger.kernel.org, rcu@vger.kernel.org, linux-mm@kvack.org Cc: cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, ming.lei@redhat.com, axboe@kernel.dk, kernel-team@fb.com, "Paul E. McKenney" Subject: [PATCH mm,percpu_ref,rcu 5/6] rcu: Make call_rcu() print mem_dump_obj() info for double-freed callback Date: Tue, 5 Jan 2021 17:17:49 -0800 Message-Id: <20210106011750.13709-5-paulmck@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20210106011603.GA13180@paulmck-ThinkPad-P72> References: <20210106011603.GA13180@paulmck-ThinkPad-P72> Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org From: "Paul E. McKenney" The debug-object double-free checks in __call_rcu() print out the RCU callback function, which is usually sufficient to track down the double free. However, all uses of things like queue_rcu_work() will have the same RCU callback function (rcu_work_rcufn() in this case), so a diagnostic message for a double queue_rcu_work() needs more than just the callback function. This commit therefore calls mem_dump_obj() to dump out any additional available information on the double-freed callback. Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Andrew Morton Cc: Reported-by: Andrii Nakryiko Signed-off-by: Paul E. McKenney --- kernel/rcu/tree.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 40e5e3d..84513c5 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2941,6 +2941,7 @@ static void check_cb_ovld(struct rcu_data *rdp) static void __call_rcu(struct rcu_head *head, rcu_callback_t func) { + static atomic_t doublefrees; unsigned long flags; struct rcu_data *rdp; bool was_alldone; @@ -2954,8 +2955,10 @@ __call_rcu(struct rcu_head *head, rcu_callback_t func) * Use rcu:rcu_callback trace event to find the previous * time callback was passed to __call_rcu(). */ - WARN_ONCE(1, "__call_rcu(): Double-freed CB %p->%pS()!!!\n", - head, head->func); + if (atomic_inc_return(&doublefrees) < 4) { + pr_err("%s(): Double-freed CB %p->%pS()!!! ", __func__, head, head->func); + mem_dump_obj(head); + } WRITE_ONCE(head->func, rcu_leak_callback); return; } -- 2.9.5