From mboxrd@z Thu Jan 1 00:00:00 1970 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 F15783446C7 for ; Thu, 13 Aug 2026 03:45:07 +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=1786592709; cv=none; b=MZBhh/QFgJaAvw1psNf3Z/BKZt0Dmgx07p3PEVAntOf84RNIjINTKlhr5aqmwgQKxlakl2Ids+ENL02pigQalrjItxNeSqfwgX7hDsGOVDgv/Rqhvqp88Tm2IGR8lpGqOkrAmfRKmhd7cl++qtuRkEHuwYCVfRlHZ3odeXJByvs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786592709; c=relaxed/simple; bh=OmfFKbf/diH5yXO2X7imO/V+oXWXz5YdZo6LCa159QQ=; h=Message-ID:Date:MIME-Version:Subject:From:To:Cc:References: In-Reply-To:Content-Type; b=a5PyahmQJBgRhNOdexPVjwzIoHSe+WeCx7uDFCyI/saqERUCYJPJhbJmAQ2s+lEjIziqWaC9ry8zZiB4mG9czPjr5ua+iRRt4Px//0fCVxrGag+qXsma0PC+1NNXvvlhSYC0b/NnSxGGxPrXpT4G5VoISSc0DM5buqv9K/W2gLY= 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=HVaI+9+D; 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="HVaI+9+D" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1786592706; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=YGaBKEdUEQkX6R8WKwZ1vLb5BxlPEDaeuLuv5j81TCM=; b=HVaI+9+D24RH22uh2Fii3A9LxuUlUM7WYE8dtPtFu5XhIj2vZ6twBF2ocVssyHfDL+D93N 2qShlfmLEhPrX7S9TABBHpACT4AFdddBViPKFt5fqjHi/p7TVKFYvudKWc8xazz6y6C5Ir 4Ao8ESDd9udLfhLH/Zty4lPM9lmibtE= Received: from mx-prod-mc-06.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-516-OR1ayQvYMUu0MTQ1M6Z2eA-1; Wed, 12 Aug 2026 23:44:56 -0400 X-MC-Unique: OR1ayQvYMUu0MTQ1M6Z2eA-1 X-Mimecast-MFC-AGG-ID: OR1ayQvYMUu0MTQ1M6Z2eA_1786592694 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-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 3C17E18001E3; Thu, 13 Aug 2026 03:44:54 +0000 (UTC) Received: from [100.91.18.181] (headnet03.pony-001.prod.iad2.dc.redhat.com [10.2.32.114]) by mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 357D1422; Thu, 13 Aug 2026 03:44:50 +0000 (UTC) Message-ID: Date: Wed, 12 Aug 2026 23:44:50 -0400 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4] sched/isolation: Defer freeing of cpumask memblock memory to initcall 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, Phil Auld References: <20260701195810.477326-1-longman@redhat.com> <6ca35731-7293-49d0-9225-b095aecd5f80@redhat.com> Content-Language: en-US In-Reply-To: <6ca35731-7293-49d0-9225-b095aecd5f80@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.6 on 10.30.177.95 On 7/29/26 1:51 PM, Waiman Long wrote: > On 7/1/26 3:58 PM, Waiman Long wrote: >> 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 memory map >>    WARNING: mm/memblock.c:904 at __free_reserved_area+0xde/0xf0, >> CPU#0: swapper/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 llist 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 cpumask memblock >> memory is treated as a llist_node with the size of a "long" type which >> is also smallest cpumask size that can be allocated. >> >> The non-atomic version of the llist APIs are used as there is no >> contention. >> >> This commit 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.com/ >> >> Fixes: 27c3a5967f05 ("sched/isolation: Convert housekeeping cpumasks >> to rcu pointers") >> Reviewed-by: Frederic Weisbecker >> Reviewed-by: Phil Auld >> Signed-off-by: Waiman Long >> --- >>   kernel/sched/isolation.c | 16 +++++++++++++++- >>   1 file changed, 15 insertions(+), 1 deletion(-) >> >>   [v4] Collect tags and update commit log >> >> 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" >>   @@ -27,6 +28,7 @@ struct housekeeping { >>   }; >>     static struct housekeeping housekeeping; >> +static __initdata LLIST_HEAD(memblock_freelist); >>     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); >>       } >>   } >>   +static int __init housekeeping_late_init(void) >> +{ >> +    struct llist_node *llnode, *pos, *t; >> + >> +    /* Free allocated memblock memory, if any */ >> +    llnode = __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) >>   { > > Ping! > > Is this patch in a state that is merge-able? Any feedback? Thanks, Longman