From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 613FD47ECD6 for ; Wed, 1 Jul 2026 13:28:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782912506; cv=none; b=PaDoak7T2hLITVucQ+L6GT26w3ghjnvIkUZ1rMC5vxpA3gdBYSNoBDF0Aj4cPZDyNQtP3vNUaIUwgkTpIUd6VjLAB0XIyAk1hjiDMj3wvMUvPb8EfwT2iiv8Ids/7A3144z7+PudhiCkfQ/lD/gCyRTvLWld+TsBb3nlboN+lLE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782912506; c=relaxed/simple; bh=XkYuH2Ol2Z0xlnmg5DTAttipv0Ks1GLp34/Pxlv7ng8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=XWN/N2ElBa6QWaGSy5XGZ3ciCOyn2K9S17Gniyhk7ULXgciNednx97kLZa7pAkJAbvNK7QZGfhFzqza/a4QcDi3CwYKwyPo/iwouqGacGWixAIyv5blqc/8TDJ3V2TQEV3nGfl9W0MMGLvYysU9JrR+3wf2qKxW0d3VTaIWWT70= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YOdUAaB8; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="YOdUAaB8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 669631F000E9; Wed, 1 Jul 2026 13:28:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782912505; bh=VpMC80M/Eld7TgPPZaVre1RCrqNu//yjhweOjXaVdMo=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=YOdUAaB86hqrxNV1vS21Goeu3nsPjA0f54lm4l0HT1IfzP8OPQztBBeifExBMB2zn o/S7AD78zuX/QT8zydipnb8/125dAiUU/Unqo4YXJhTLB9UxhriDNv0xvLOghC4VxZ PUwJcsYdeQJJ28dt/7qhJboUrz7JEL8DDCszr3oqPdLvyXqk2C+RebfHE5uQ2S93zc IN68r633SLrT2ltqoVlEUbjhLFZwwz8G0xp02zM64USS9xObaOLh5D7biHibPi8lxh QDRs7vlP0KzLFZkjpMypOoQHK9wnJjGKuGq0+DwKK3bMjp1vVo4HvRaV9Qb6WgWaYK q90w8J9AoUo9w== Date: Wed, 1 Jul 2026 15:28:22 +0200 From: Frederic Weisbecker To: Waiman Long Cc: Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , linux-kernel@vger.kernel.org Subject: Re: [PATCH v3.1] sched/isolation: Defer freeing of cpumask memblock memory to initcall Message-ID: References: <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-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260604182440.430811-1-longman@redhat.com> Le Thu, Jun 04, 2026 at 02:24:40PM -0400, Waiman Long a écrit : > 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 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.com/ > > Fixes: 27c3a5967f05 ("sched/isolation: Convert housekeeping cpumasks to rcu pointers") > Signed-off-by: Waiman Long Reviewed-by: Frederic Weisbecker -- Frederic Weisbecker SUSE Labs