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 6DFD337E2E5 for ; Thu, 4 Jun 2026 18:25:02 +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=1780597504; cv=none; b=qt1gxwSPT9vIkr/w+eMluy1YNIOsFTj0jxGdON8R28z6cU0HcyjXDo06lkYZyZurkA7h0SeGfKZe67aONAf+KYgW3wMHsYXaxy3ZlyqilVKTOQI65Q3LUjEFZ+RHOTlrNs7bmXvINe5fMNSAiErcHnLagQ/M9Mx4AwAcmxr8Lmw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780597504; c=relaxed/simple; bh=oCl9MHByurSGXmAMEwWEP6KcbcVq8ATqV3687J6bX5I=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=ellGYWjBLuxO8qCFOB5lHF4cvwOPF41GTbTee9I5PBxyk9gW7KO5CkhHzMpnk+Ntq1yMs1I+deH6pCSjKI6rxKw2Nglrh2+TE7cHCbSJMi9DIW/21gZLpWlbWgAg32CXIS7/jbdxGMlSiRMrdiGJmS8IXIDHAHDi3YP0bkSc33c= 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=GDHrNuPM; 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="GDHrNuPM" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1780597501; 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=dWjrpZ1jVXRaVsb+S9T2b2okOnv+c12lQZMrXZT0UV4=; b=GDHrNuPMy582EVxLhegUPEOich6+1oYS1ly5Gk7/vPwSp8pD/HZ1Q6ylsWcri90lKSN9WT /g9u7fl6xIJyWVTcOuErb7Vym0mNXZPFxlP3lmJE/tz0mMZX+N8IRgltQYaqdd6KHj6E9F Qw3tNT3MAX9GIeF9iS1jkUVzZOD1dPU= Received: from mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-622-sU3E9OdcOQSm8WvML8S-JA-1; Thu, 04 Jun 2026 14:24:57 -0400 X-MC-Unique: sU3E9OdcOQSm8WvML8S-JA-1 X-Mimecast-MFC-AGG-ID: sU3E9OdcOQSm8WvML8S-JA_1780597495 Received: from mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.95]) (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-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id CDA8F1956096; Thu, 4 Jun 2026 18:24:54 +0000 (UTC) Received: from llong-thinkpadp16vgen1.westford.csb (unknown [10.22.88.175]) by mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 70682763; Thu, 4 Jun 2026 18:24:52 +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 v3.1] sched/isolation: Defer freeing of cpumask memblock memory to initcall Date: Thu, 4 Jun 2026 14:24:40 -0400 Message-ID: <20260604182440.430811-1-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 3.6 on 10.30.177.95 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(-) [v3.1] Add __initdata to memblock_freelist diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c index ef152d401fe2..156025ef81b7 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 __initdata LLIST_HEAD(memblock_freelist); =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