From nobody Mon Jun 8 08:28:39 2026 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 340D7212B2F for ; Thu, 4 Jun 2026 17:51:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780595508; cv=none; b=cRnkVDDoM/L/Xuik4D/BA0kE+mDclYtC7XzOWiKGxS+6D6Qo44po31jmnY6ijC9+8fC9nTauUtVlAJAHL2syRIKWRk7501CPpKyEXyXKw4P4Vs1lIaDDVyhMpVOCxPN4AUHlq+qlo/+Ly4/07NJuz02oCuJWKjRA1oUPM78M9nI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780595508; c=relaxed/simple; bh=FzrQEox0X1c8XleLDedWHVBpIFPQPiMIziTWiD3hlrk=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=r4udwjqzoSL87rq/i/mCiddHSEclxAwW9JE7yXDUJMREIwnhAyWTIiOkKyAEYcM0Y7FdiN0Al1m2BvdiZFn2z5XE76JRTtiVKxVkLc0U3ktAphLMzZbQU/hLeThPI9oWma3EQLxgtV5DufWtov+x4aTftjXmhuuy1Hng6Y0YxuM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=WUvDKoAJ; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="WUvDKoAJ" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1780595506; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=w43/ldFyyoOkjReA776UUW/4XEw63z0s1j9TlAjLMHI=; b=WUvDKoAJHeX2Vrv+DkzpxXoeqUYbGKFDewgzHp+OC+qAhCfy3ypJZC2jazJ/H0niRAYukT 0PAgvsyTjuNweIaGm9qCyObd1TGH2QExtfwN4Wxxqt2NKMbWLQlZHy9iHDpF/SVKX6r3oX UkRGdwnkrrfX6Ahgt4AKo31KggiSRa4= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-228-whY06J-LNA6vpwes-Vkmaw-1; Thu, 04 Jun 2026 13:51:42 -0400 X-MC-Unique: whY06J-LNA6vpwes-Vkmaw-1 X-Mimecast-MFC-AGG-ID: whY06J-LNA6vpwes-Vkmaw_1780595501 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 9BB3E1801373; Thu, 4 Jun 2026 17:51:40 +0000 (UTC) Received: from llong-thinkpadp16vgen1.westford.csb (unknown [10.22.88.175]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id BEA18180049F; Thu, 4 Jun 2026 17:51:37 +0000 (UTC) From: Waiman Long To: Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , Frederic Weisbecker Cc: linux-kernel@vger.kernel.org, Waiman Long Subject: [PATCH v3] sched/isolation: Defer freeing of cpumask memblock memory to initcall Date: Thu, 4 Jun 2026 13:51:22 -0400 Message-ID: <20260604175122.422219-1-longman@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Content-Type: text/plain; charset="utf-8" When testing a linux-next kernel with commit 59bd1d914bb5 ("memblock: warn when freeing reserved memory before memory map is initialized"), the following warning was hit when there was a "nohz_full" kernel boot parameter. Cannot free reserved memory because of deferred initialization of the mem= ory map WARNING: mm/memblock.c:904 at __free_reserved_area+0xde/0xf0, CPU#0: swap= per/0/0 : Call Trace: memblock_phys_free+0xcb/0x100 housekeeping_init+0x14c/0x170 start_kernel+0x207/0x450 x86_64_start_reservations+0x24/0x30 x86_64_start_kernel+0xda/0xe0 common_startup_64+0x13e/0x141 IOW, we shouldn't free memblock allocated memory so early in the boot process when memory map isn't fully initialized in deferred_init_memmap(). Fix it by saving the housekeeping cpumask memblock memory to be freed into a free list in housekeeping_init() and add a new housekeeping_late_init() helper to defer the actual freeing of memblock memory to when initcall's are being processed. The non-atomic version of the llist APIs are used as there is no contention. This commit also depends on the presence of commit 7c2eee9c1367 ("memblock: don't touch memblock arrays when memblock_free() is called late") to prevent a KASAN UAF bug report [1]. [1] https://lore.kernel.org/lkml/20260505051821.1107133-1-longman@redhat.c= om/ Fixes: 27c3a5967f05 ("sched/isolation: Convert housekeeping cpumasks to rcu= pointers") Signed-off-by: Waiman Long --- kernel/sched/isolation.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c index ef152d401fe2..e04652f55a0e 100644 --- a/kernel/sched/isolation.c +++ b/kernel/sched/isolation.c @@ -8,6 +8,7 @@ * */ #include +#include #include #include "sched.h" =20 @@ -27,6 +28,7 @@ struct housekeeping { }; =20 static struct housekeeping housekeeping; +static LLIST_HEAD(memblock_freelist); /* List of memblock memory to be fre= ed */ =20 bool housekeeping_enabled(enum hk_type type) { @@ -189,10 +191,22 @@ void __init housekeeping_init(void) WARN_ON_ONCE(cpumask_empty(omask)); cpumask_copy(nmask, omask); RCU_INIT_POINTER(housekeeping.cpumasks[type], nmask); - memblock_free(omask, cpumask_size()); + __llist_add((struct llist_node *)omask, &memblock_freelist); } } =20 +static int __init housekeeping_late_init(void) +{ + struct llist_node *llnode, *pos, *t; + + /* Free allocated memblock memory, if any */ + llnode =3D __llist_del_all(&memblock_freelist); + llist_for_each_safe(pos, t, llnode) + memblock_free(pos, cpumask_size()); + return 0; +} +pure_initcall(housekeeping_late_init); + static void __init housekeeping_setup_type(enum hk_type type, cpumask_var_t housekeeping_staging) { --=20 2.54.0