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 7B57BC43334 for ; Fri, 17 Jun 2022 02:50:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1379847AbiFQCuo (ORCPT ); Thu, 16 Jun 2022 22:50:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60368 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1379822AbiFQCtw (ORCPT ); Thu, 16 Jun 2022 22:49:52 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DD0C465432 for ; Thu, 16 Jun 2022 19:49:48 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 92A59B826F5 for ; Fri, 17 Jun 2022 02:49:47 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5695FC34114; Fri, 17 Jun 2022 02:49:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1655434186; bh=aDLbNBNUTTjtHQmSQ2f4HJN+Wt7rSz8kUmF22gTO2m0=; h=Date:To:From:Subject:From; b=Bw+vQbuU/12DC1H1NFHNbI9SokowZxkimqM1ORsop/z7oR9LFNe/WJdyYfqATd/CK I69j6O9pqmwShRP0dkRpS4If0k1JzoIAemQsYaipbNjl81NispC7C7cXdHiNGiAnPf Q9aVDixsIA4AO2ebj6YRK5gRrdJxnTf3YdUsE5Cc= Date: Thu, 16 Jun 2022 19:49:45 -0700 To: mm-commits@vger.kernel.org, songmuchun@bytedance.com, catalin.marinas@arm.com, longman@redhat.com, akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-stable] mm-kmemleak-prevent-soft-lockup-in-first-object-iteration-loop-of-kmemleak_scan.patch removed from -mm tree Message-Id: <20220617024946.5695FC34114@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The quilt patch titled Subject: mm/kmemleak: prevent soft lockup in first object iteration loop of kmemleak_scan() has been removed from the -mm tree. Its filename was mm-kmemleak-prevent-soft-lockup-in-first-object-iteration-loop-of-kmemleak_scan.patch This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Waiman Long Subject: mm/kmemleak: prevent soft lockup in first object iteration loop of kmemleak_scan() Date: Tue, 14 Jun 2022 18:03:59 -0400 The first RCU-based object iteration loop has to modify the object count. So we cannot skip taking the object lock. One way to avoid soft lockup is to insert occasional cond_resched() call into the loop. This cannot be done while holding the RCU read lock which is to protect objects from being freed. However, taking a reference to the object will prevent it from being freed. We can then do a cond_resched() call after every 64k objects safely. Link: https://lkml.kernel.org/r/20220614220359.59282-4-longman@redhat.com Signed-off-by: Waiman Long Reviewed-by: Catalin Marinas Cc: Muchun Song Signed-off-by: Andrew Morton --- mm/kmemleak.c | 28 +++++++++++++++++++++++++++- 1 file changed, 27 insertions(+), 1 deletion(-) --- a/mm/kmemleak.c~mm-kmemleak-prevent-soft-lockup-in-first-object-iteration-loop-of-kmemleak_scan +++ a/mm/kmemleak.c @@ -1474,12 +1474,16 @@ static void kmemleak_scan(void) struct zone *zone; int __maybe_unused i; int new_leaks = 0; + int loop1_cnt = 0; jiffies_last_scan = jiffies; /* prepare the kmemleak_object's */ rcu_read_lock(); list_for_each_entry_rcu(object, &object_list, object_list) { + bool obj_pinned = false; + + loop1_cnt++; raw_spin_lock_irq(&object->lock); #ifdef DEBUG /* @@ -1505,10 +1509,32 @@ static void kmemleak_scan(void) /* reset the reference count (whiten the object) */ object->count = 0; - if (color_gray(object) && get_object(object)) + if (color_gray(object) && get_object(object)) { list_add_tail(&object->gray_list, &gray_list); + obj_pinned = true; + } raw_spin_unlock_irq(&object->lock); + + /* + * Do a cond_resched() to avoid soft lockup every 64k objects. + * Make sure a reference has been taken so that the object + * won't go away without RCU read lock. + */ + if (!(loop1_cnt & 0xffff)) { + if (!obj_pinned && !get_object(object)) { + /* Try the next object instead */ + loop1_cnt--; + continue; + } + + rcu_read_unlock(); + cond_resched(); + rcu_read_lock(); + + if (!obj_pinned) + put_object(object); + } } rcu_read_unlock(); _ Patches currently in -mm which might be from longman@redhat.com are