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 15B2FFA3743 for ; Fri, 28 Oct 2022 21:07:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229788AbiJ1VHJ (ORCPT ); Fri, 28 Oct 2022 17:07:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52708 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229828AbiJ1VHH (ORCPT ); Fri, 28 Oct 2022 17:07:07 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C734C1DD88C; Fri, 28 Oct 2022 14:07:06 -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 dfw.source.kernel.org (Postfix) with ESMTPS id 636AF629FD; Fri, 28 Oct 2022 21:07:06 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A9DF0C433C1; Fri, 28 Oct 2022 21:07:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1666991225; bh=OdHZqnmGvOWMhBMsP6mONPB7VY+f5C4giJd2cIR04vE=; h=Date:To:From:Subject:From; b=VlyqDzaiJjTbCBhsnwiq1dhffqSALLY0FynxWjQjQKhFtEu825JJvbv6YL+vI1TYt 71u3mKMHmaVgx1AyIIFp8Bi0zJoYIZcNkA9aR0PiVvghQn0FHe+4r8mdLQs4ODd68C qKhI9bqrdbpdTmKKTQQx2yYoEmPzqbYxhVgIGG+Q= Date: Fri, 28 Oct 2022 14:07:04 -0700 To: mm-commits@vger.kernel.org, stable@vger.kernel.org, songmuchun@bytedance.com, catalin.marinas@arm.com, longman@redhat.com, akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-hotfixes-stable] mm-kmemleak-prevent-soft-lockup-in-kmemleak_scans-object-iteration-loops.patch removed from -mm tree Message-Id: <20221028210705.A9DF0C433C1@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 kmemleak_scan()'s object iteration loops has been removed from the -mm tree. Its filename was mm-kmemleak-prevent-soft-lockup-in-kmemleak_scans-object-iteration-loops.patch This patch was dropped because it was merged into the mm-hotfixes-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Waiman Long Subject: mm/kmemleak: prevent soft lockup in kmemleak_scan()'s object iteration loops Date: Thu, 20 Oct 2022 13:56:19 -0400 Commit 6edda04ccc7c ("mm/kmemleak: prevent soft lockup in first object iteration loop of kmemleak_scan()") adds cond_resched() in the first object iteration loop of kmemleak_scan(). However, it turns that the 2nd objection iteration loop can still cause soft lockup to happen in some cases. So add a cond_resched() call in the 2nd and 3rd loops as well to prevent that and for completeness. Link: https://lkml.kernel.org/r/20221020175619.366317-1-longman@redhat.com Fixes: 6edda04ccc7c ("mm/kmemleak: prevent soft lockup in first object iteration loop of kmemleak_scan()") Signed-off-by: Waiman Long Cc: Catalin Marinas Cc: Muchun Song Cc: Signed-off-by: Andrew Morton --- --- a/mm/kmemleak.c~mm-kmemleak-prevent-soft-lockup-in-kmemleak_scans-object-iteration-loops +++ a/mm/kmemleak.c @@ -1461,6 +1461,27 @@ static void scan_gray_list(void) } /* + * Conditionally call resched() in a object iteration loop while making sure + * that the given object won't go away without RCU read lock by performing a + * get_object() if !pinned. + * + * Return: false if can't do a cond_resched() due to get_object() failure + * true otherwise + */ +static bool kmemleak_cond_resched(struct kmemleak_object *object, bool pinned) +{ + if (!pinned && !get_object(object)) + return false; + + rcu_read_unlock(); + cond_resched(); + rcu_read_lock(); + if (!pinned) + put_object(object); + return true; +} + +/* * Scan data sections and all the referenced memory blocks allocated via the * kernel's standard allocators. This function must be called with the * scan_mutex held. @@ -1471,7 +1492,7 @@ static void kmemleak_scan(void) struct zone *zone; int __maybe_unused i; int new_leaks = 0; - int loop1_cnt = 0; + int loop_cnt = 0; jiffies_last_scan = jiffies; @@ -1480,7 +1501,6 @@ static void kmemleak_scan(void) list_for_each_entry_rcu(object, &object_list, object_list) { bool obj_pinned = false; - loop1_cnt++; raw_spin_lock_irq(&object->lock); #ifdef DEBUG /* @@ -1514,24 +1534,11 @@ static void kmemleak_scan(void) 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. + * Do a cond_resched() every 64k objects to avoid soft lockup. */ - 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); - } + if (!(++loop_cnt & 0xffff) && + !kmemleak_cond_resched(object, obj_pinned)) + loop_cnt--; /* Try again on next object */ } rcu_read_unlock(); @@ -1598,8 +1605,16 @@ static void kmemleak_scan(void) * scan and color them gray until the next scan. */ rcu_read_lock(); + loop_cnt = 0; list_for_each_entry_rcu(object, &object_list, object_list) { /* + * Do a cond_resched() every 64k objects to avoid soft lockup. + */ + if (!(++loop_cnt & 0xffff) && + !kmemleak_cond_resched(object, false)) + loop_cnt--; /* Try again on next object */ + + /* * This is racy but we can save the overhead of lock/unlock * calls. The missed objects, if any, should be caught in * the next scan. @@ -1632,8 +1647,16 @@ static void kmemleak_scan(void) * Scanning result reporting. */ rcu_read_lock(); + loop_cnt = 0; list_for_each_entry_rcu(object, &object_list, object_list) { /* + * Do a cond_resched() every 64k objects to avoid soft lockup. + */ + if (!(++loop_cnt & 0xffff) && + !kmemleak_cond_resched(object, false)) + loop_cnt--; /* Try again on next object */ + + /* * This is racy but we can save the overhead of lock/unlock * calls. The missed objects, if any, should be caught in * the next scan. _ Patches currently in -mm which might be from longman@redhat.com are