linux-kernel - Re: [PATCH v3] mm/mm_init: Don't cond_resched() in deferred_init_memmap_chunk() if called from deferred_grow

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Message-ID: <20260123072422.rOwJDb5K@linutronix.de>
Date: Fri, 23 Jan 2026 08:24:22 +0100
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Waiman Long <longman@...hat.com>
Cc: Mike Rapoport <rppt@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Clark Williams <clrkwllms@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, linux-rt-devel@...ts.linux.dev,
	Wei Yang <richard.weiyang@...il.com>,
	David Hildenbrand <david@...nel.org>,
	"Paul E . McKenney" <paulmck@...nel.org>
Subject: Re: [PATCH v3] mm/mm_init: Don't cond_resched() in
 deferred_init_memmap_chunk() if called from deferred_grow_zone()

On 2026-01-22 13:43:43 [-0500], Waiman Long wrote:
…
> 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

I would strip this report because the call chain is simple and there
just one so it is not one of many and hard to find. 

…
> 
> Fixes: 3acb913c9d5b ("mm/mm_init: use deferred_init_memmap_chunk() in deferred_grow_zone()")
> Suggested-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> Signed-off-by: Waiman Long <longman@...hat.com>

Reviewed-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>

Sebastian