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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 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 X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 16E8A20003 X-Stat-Signature: 11ex3pc9jiyhs3whfy4mestwqc1zxcp3 X-HE-Tag: 1784120856-404822 X-HE-Meta: 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 j4hvz17W gPG6+pXhdW4p4fnbVtl/J9FmT3dPg0nO0F5sf79ua6VvvA9PEMA4l1ediuv4B9+0WH8jOhd/d/AGNmj22UOu+ZrOxJQ8TFCyTB2UD0p5h3ktQJphpWnxTH4aedv3tGbCkkurbPVXfOIYxSS7EHt8/G+Khqfz5F+fWovWaMugzuidL+dQ7ODBBmYtIRkAMto4uFJZg7Wc1jsHG+HE8Zq2Y17sjTBPPdAAbKqcS44xXTuKvu69m2JQbd2t8OV4ACQcFeO9HLEcfl7QakOr2lpyaEaV+aXABbIlFkoQ1eBVignIsnOVxhjgsrNJqjR/F4gzp32foNQtmrm69dsR9ejbs/DF7Ot3Y6284Rm5ZMUg5p9W2hbARF9b7T3LvyQoc7+LWYhoHcRJ4yatrF8Sc0BwlBaC88pmkApAs+Vwc Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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; > } >