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 B016542047D; Wed, 15 Jul 2026 13:07:36 +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=1784120857; cv=none; b=bQnAmJPYL88KiUk/jebW9x6pRBdKzl15/mnZioQD43ENJnr2VVBk8Wh0ZYu1UQd9WxYiVOSgWmhCwLmmRtKCbY1rpYVOcl/fWwUzmhQhRj9FJOL8CYe52H/DBrlShob714WW3J9fQyoKAjX2QUsxDbB1vyFMWm3Y5Z4E+xAyg5k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784120857; c=relaxed/simple; bh=DjcRn5ZkjcgM9pbNl3OBX9Ay6Rvmd6QgbWvMvRAoF7A=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=iCNb1hG5iAbQjVH61kw9otONOjhU2EvuOQGQgNpKjOdmHWhUNA6ecHUAAy/JQgRl3F2fvCdqE7guq2Iomh4FbFZubngtU/+S+BTXYlqVky2cL6Cc3XFIMWMyZeqOqoRhYA60oO5KX2sqv427BpR+j2DPYXon0sapEeDCAY6JKAw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=m3glXrb9; 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="m3glXrb9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0BC761F000E9; Wed, 15 Jul 2026 13:07:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784120856; bh=O2F8hSkyxebJB6yvztXLwkydTDbTUZP1WcynsWPDoCo=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=m3glXrb9v3mZSRxk0REyXt42oVh1w7J7h0aRKC9T9OILn9Xy1ig6Kz7qBBTdVH+du sx2c8eH/wkqai7SxX0lb7UrW59LohFuDh1VPy1IDmGLk4jpQx8d86NJz8Cx9WwN8UE iv/otT8uKxl0p1q2WuodfZ4McHV3QVwS0IEDVn06qFaNL/SSuN2q1wUz28Qdx6HaD/ GcFvJ/b7flfjW4pMUa/yCxDWz37QuW2GTHDWnqsDf5ODBCd6ga5xpoQ7UhdG2CcK4X dlVjnYObKT7rpzO+zJ8moBz+5KTrsmLoje3xP76Z0NgavA1DeIbUiCB0QEm5z7PwE3 JCeC5KzKFUSMA== Message-ID: <5d7664d7-5b86-462b-adea-4086c21756c4@kernel.org> Date: Wed, 15 Jul 2026 15:07:30 +0200 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 2/2] mm/page_alloc: don't spin_trylock() when disallowed in free_one_page() Content-Language: en-US To: Brendan Jackman , Andrew Morton , Suren Baghdasaryan , Michal Hocko , Johannes Weiner , Zi Yan , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt , Alexei Starovoitov , Harry Yoo , Shakeel Butt Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, sashiko-bot@kernel.org References: <20260715-alloc-nolock-fixes-v1-0-fadc49952dda@google.com> <20260715-alloc-nolock-fixes-v1-2-fadc49952dda@google.com> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/15/26 11:03, Brendan Jackman wrote: > __free_frozen_pages() checks can_spin_trylock() before entering into the > main free_frozen_page_commit()/free_one_page() path, but before this it > can get to free_one_page() via the !pcp_allowed_order() and > MIGRATE_ISOLATE paths. > > The !pcp_allowed_order() path depends on usage by callers so might not > be possible in practice. The MIGRATE_ISOLATE path probably means kernel > crashes and privilege escalation if anyone ever did memory hotplug and > BPF tracing on a PREEMPT_RT or !SMP build. > > Cc: stable@vger.kernel.org > Fixes: 8c57b687e8331 ("mm, bpf: Introduce free_pages_nolock()") > Reported-by: sashiko-bot@kernel.org > Link: https://sashiko.dev/#/patchset/20260710-spin-trylock-followup-v1-0-affb5fe5ed00%40google.com?part=2 Closes: also > Signed-off-by: Brendan Jackman Reviewed-by: Vlastimil Babka (SUSE) > --- > mm/page_alloc.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 5f9873dfccc5a..46e5ea59c71df 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1559,7 +1559,7 @@ static void free_one_page(struct zone *zone, struct page *page, > unsigned long flags; > > if (unlikely(fpi_flags & FPI_TRYLOCK)) { > - if (!spin_trylock_irqsave(&zone->lock, flags)) { > + if (!can_spin_trylock() || !spin_trylock_irqsave(&zone->lock, flags)) { > add_page_to_zone_llist(zone, page, order); > return; > } >