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Wed, 21 Jan 2026 14:11:03 -0500 X-MC-Unique: XN4vaPV7PW6RxpaJHQxHwg-1 X-Mimecast-MFC-AGG-ID: XN4vaPV7PW6RxpaJHQxHwg_1769022662 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (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-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 956081956096; Wed, 21 Jan 2026 19:11:01 +0000 (UTC) Received: from llong-thinkpadp16vgen1.westford.csb (unknown [10.22.89.197]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 3C42919560A2; Wed, 21 Jan 2026 19:10:59 +0000 (UTC) From: Waiman Long To: Mike Rapoport , Andrew Morton , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, Wei Yang , David Hildenbrand , Waiman Long Subject: [PATCH] mm/mm_init: Don't call cond_resched() in deferred_init_memmap_chunk() if rcu_preempt_depth() set Date: Wed, 21 Jan 2026 14:10:36 -0500 Message-ID: <20260121191036.461389-1-longman@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 X-Rspam-User: X-Rspamd-Queue-Id: D8805C000B X-Rspamd-Server: rspam07 X-Stat-Signature: rzre8ofc97fduh1zgeq43ozeoqq3dex5 X-HE-Tag: 1769022667-472743 X-HE-Meta: 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 y7B5nBKF D4IVb26Cr9FZerBj/mNsx81+qpbK8vxU+HZU2mGzY9mzFUJOo6CCBDgBdCIj+Te4EYCw9hjGMSwDAuU/mAG6n35qcaMHw95pflqp4mOmpP50CeYCF2RHfEMAbuepNbDbDrpIQSa5yJcOCLbuf1W9MfnElIO+ZF6RW+Isk26a1IHsW7vz1uY685OPSDt8vFLiHWauOv7xsjBhfZbhveN/Vpyej4GNg9/ViOtcZIo7MV9E4EFnZw6hjZFqU0f/CzQ0IcstEK/JHRxEowSWLrm3FUgusdnesqthjSw6at5e6KTVA6ZAhrKrmMyGOxl1928qVuQMkqw7FS4eflC/fetLyqsqYd4O5saVas3J6T4Mx5cnO+fgJnbQQDSc7I42DX5bG7vKo3sjJFVPXpZl95O91p3ExRtrqr3l+UU1dpb3BY5xHUHQ99Zef8CLbnoVKddnK8k4w X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Commit 3acb913c9d5b ("mm/mm_init: use deferred_init_memmap_chunk() in deferred_grow_zone()") made deferred_grow_zone() call deferred_init_memmap_chunk() within a pgdat_resize_lock() critical section with irqs disabled. It did check for irqs_disabled() in deferred_init_memmap_chunk() to avoid calling cond_resched(). For a PREEMPT_RT kernel build, however, spin_lock_irqsave() does not disable interrupt but rcu_read_lock() is called. This leads to the following bug report. BUG: sleeping function called from invalid context at mm/mm_init.c:2091 in_atomic(): 0, irqs_disabled(): 0, non_block: 0, pid: 1, name: swapper/0 preempt_count: 0, expected: 0 RCU nest depth: 1, expected: 0 3 locks held by swapper/0/1: #0: ffff80008471b7a0 (sched_domains_mutex){+.+.}-{4:4}, at: sched_domains_mutex_lock+0x28/0x40 #1: ffff003bdfffef48 (&pgdat->node_size_lock){+.+.}-{3:3}, at: deferred_grow_zone+0x140/0x278 #2: ffff800084acf600 (rcu_read_lock){....}-{1:3}, at: rt_spin_lock+0x1b4/0x408 CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Tainted: G W 6.19.0-rc6-test #1 PREEMPT_{RT,(full) } Tainted: [W]=WARN Call trace: show_stack+0x20/0x38 (C) dump_stack_lvl+0xdc/0xf8 dump_stack+0x1c/0x28 __might_resched+0x384/0x530 deferred_init_memmap_chunk+0x560/0x688 deferred_grow_zone+0x190/0x278 _deferred_grow_zone+0x18/0x30 get_page_from_freelist+0x780/0xf78 __alloc_frozen_pages_noprof+0x1dc/0x348 alloc_slab_page+0x30/0x110 allocate_slab+0x98/0x2a0 new_slab+0x4c/0x80 ___slab_alloc+0x5a4/0x770 __slab_alloc.constprop.0+0x88/0x1e0 __kmalloc_node_noprof+0x2c0/0x598 __sdt_alloc+0x3b8/0x728 build_sched_domains+0xe0/0x1260 sched_init_domains+0x14c/0x1c8 sched_init_smp+0x9c/0x1d0 kernel_init_freeable+0x218/0x358 kernel_init+0x28/0x208 ret_from_fork+0x10/0x20 Fix it by checking rcu_preempt_depth() as well to prevent calling cond_resched(). Note that CONFIG_PREEMPT_RCU should always be enabled in a PREEMPT_RT kernel. Fixes: 3acb913c9d5b ("mm/mm_init: use deferred_init_memmap_chunk() in deferred_grow_zone()") Signed-off-by: Waiman Long --- mm/mm_init.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/mm/mm_init.c b/mm/mm_init.c index fc2a6f1e518f..4d6b6dac6f58 100644 --- a/mm/mm_init.c +++ b/mm/mm_init.c @@ -2085,7 +2085,12 @@ deferred_init_memmap_chunk(unsigned long start_pfn, unsigned long end_pfn, spfn = chunk_end; - if (irqs_disabled()) + /* + * pgdat_resize_lock() only disables irqs in non-RT + * kernels but calls rcu_read_lock() in a PREEMPT_RT + * kernel. + */ + if (irqs_disabled() || rcu_preempt_depth()) touch_nmi_watchdog(); else cond_resched(); -- 2.52.0