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Tue, 27 Oct 2026 10:43:07 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Tue, 27 Oct 2026 18:43:04 +0100 To: sashiko-reviews@lists.linux.dev Cc: "Uladzislau Rezki (Sony)" , linux-mm@kvack.org, Andrew Morton , Baoquan He , "David Hildenbrand (Arm)" Subject: Re: [PATCH] mm/vmalloc: Bail out if in softirq context Message-ID: References: <20261026102503.30860-1-urezki@gmail.com> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: q3beux9een86og6ijr847aze1ruhyaxy X-Spam-Status: No, score=-7.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_PASS,SPF_PASS autolearn=no autolearn_force=no version=4.0.1 X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 28BD380002 X-Rspam-User: X-HE-Tag: 1793122989-331007 X-HE-Meta: U2FsdGVkX1+//YXWHREcNNiOQQHvBePmmJPwD4BCX28t65bZYZGFb+Eo4rRkm3DMWSqjJxedFH3r795F3Oy3TSVD6wnOLhkl/vFkwLXtLCQvXARChItJerqxLTTb1jmYJsGkBfPkfD3kySgysd1rpx9NVOsYdvM6qTYIH3i9EMZ5fSSATF6KzJSn/OA4o8z5fX9+qUEy8G6s0fs0a5jSE0fs/n77+UslvwZweWtxJI84LcDInzknLdaJYsP8HT+7nkyNnSQoq3EPS5EGtKuExdh/IUC8NvHd1kW2n1v15WZ13Fk1X1l60Hdy2w0Cx2IMIQbfJBCaYKfJeuiKGZTUVl++O1eOB2PiWAQEZAlYZan0pmg3FQ3tEadJWO58D0e1IdoHra9hoYYVjK6RkQngO2+2n3lg1BK1xx/qozSf/4VqkYLTEne/L7dlr/mS0lxetVoIxmXZBtowo3lZ7h8U8ygG0C/pQd/+1aUwehK44Tc3tjSnnnYy286lnu6HyHdLyuC7nAh00TnovbFkFwPfXHe+5HhQ7gQrmnM3NV17z4Sk0gA4Rg/5jCQFS5vgUHPnw/2+Yw98J2FOd3xHV76Ao4ZxmOQ11/WDgk8cBcukv82u2s6rmR96rNDAdnvYuJdvsoKOWQRisPQVir6X8AWaIqs+a/3dvtBY5Ofk8uJyd+HH8Jli1sNZQvuBaoQNEBelSZZsEeqbPF4njF+6HAZzMasLdV3y/1KQXSyS2+JIUoPDG3kVPyef78qy7Q4E3ScYbGi/dq4cOVlqt9ewnxNNhqkLVjq7lOS51zShmnWXEVM3sPCqbh/kMy3Qt8GBff262+XKZdakJp6LkD86jcxYYtq/gSjZDO+3GsHbBgo6VAZAhEvcxm7tGH7yuA1PvCrGY/+zWFP4Azx9H81sfKv1SFehxHj+cORWtL2iag434pmDrem7ANKevoPyiwEMh28kdmlnwIXTEVEu0CpcJZC X3+v6eI6 3JmfeNDpj+n5xAwTgO3n5eYjQTbkmFW8HttVB3V1JoP8qSXWqYkik9iWpVMcYH4vx97dSU4gR7aU2bYaZv8BTVHSVx3hB0UlldeADgvCyYQ6m54EEIxkLr7S/YSgA1qO92jESyXeT9zD1rh9Z/WV/yxYwX/b3c/jancuLgIZHz0LeEqWMOY2rvXTQWZ8rI1UrI+KGSm0zegHVrJGj8vlRUeFNp7luL6N8kmMa/fi8JNCVYvXEcRH1tEm80gXmZV6/nw7f67SmPbAxxZQsiK2+pRxA07UNHR4kDcAQB3tsxLJ7ZsT364g2/xgM6d9odLll13FuIiI/LXcJc7W8H+p7gNHpVnF7vcduq1BPEn2LtY67ODIRlcXrmiOxNmkrPr9lMNp0SyVJ8O0MN8fNTrpWb8aSXht9jusiltI44aP5LhgzxK9v7214aIgbd63ZB3b//fHph9eqU9GGAIcQC6yNerdO7vjknoM0cjTSHI6iuuTs8G8= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Tue, Oct 27, 2026 at 10:25:23AM +0000, sashiko-bot@kernel.org wrote: > Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider: > - [High] mm/vmalloc: ABBA deadlock when calling vmalloc() with BH or IRQs disabled > - [Medium] mm/vmalloc: __get_vm_area_node() irq bailout triggers warnings and retry > -- > > commit 9fea18279139941aa247a1a577dd5e101116871a > Author: Uladzislau Rezki (Sony) > > mm/vmalloc: Bail out if in softirq context > > This commit restores a softirq check in __get_vm_area_node() using > in_serving_softirq() so that vmalloc() bails out when invoked from softirq > context while still permitting callers with disabled bottom halves. It also > replaces BUG_ON(in_nmi() || in_hardirq()) with a WARN_ON_ONCE() check that > returns NULL. > > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > > index 44e0eb32708f1..5a949525b9db8 100644 > > --- a/mm/vmalloc.c > > +++ b/mm/vmalloc.c > > @@ -3271,7 +3271,13 @@ struct vm_struct *__get_vm_area_node(unsigned long size, > > struct vm_struct *area; > > unsigned long requested_size = size; > > > > - BUG_ON(in_nmi() || in_hardirq()); > > + /* IRQ re-entrancy -> irq_exit() -> process softirq. */ > > + if (in_serving_softirq()) > > + return NULL; > > + > > + if (WARN_ON_ONCE(in_nmi() || in_hardirq())) > > + return NULL; > > [Severity: High] > Can allowing vmalloc() in task context with bottom halves or interrupts > disabled still cause a multi-CPU ABBA deadlock on vmalloc's internal locks? > CPU_0 CPU_1 vmalloc() lock(B) lock(A) vmalloc() soft-irq lock(A) lock(B) Such callers have to be fixed at their call sites. __get_vm_area_node() cannot detect ABBA deadlock which involves a lock held by a task-context caller. -- Uladzislau Rezki