From: "David Hildenbrand (Arm)" <david@kernel.org>
To: Georgi Djakov <georgi.djakov@oss.qualcomm.com>,
akpm@linux-foundation.org
Cc: linux-mm@kvack.org, linux-cxl@vger.kernel.org, osalvador@suse.de,
gregkh@linuxfoundation.org, rafael@kernel.org, djakov@kernel.org
Subject: Re: [PATCH] drivers/base/memory: set mem->altmap after successful device registration
Date: Wed, 13 May 2026 15:20:21 +0200 [thread overview]
Message-ID: <a3eea8f4-d693-41da-b8ab-764e6ce311ad@kernel.org> (raw)
In-Reply-To: <f25f1ef0-5359-4c00-920d-cdfc37cda968@kernel.org>
On 5/13/26 15:14, David Hildenbrand (Arm) wrote:
> On 5/13/26 15:09, Georgi Djakov wrote:
>> If __add_memory_block() fails at xa_store() (under memory pressure
>> for example), device_unregister() is called, which eventually
>> triggers memory_block_release() with mem->altmap still set, causing
>> a WARN_ON(mem->altmap).
>>
>> WARNING: CPU: 1 PID: 76 at drivers/base/memory.c:96 memory_block_release+0x28/0x30
>> Call trace:
>> memory_block_release+0x28/0x30 (P)
>> kobject_put+0xc8/0x1bc
>> device_unregister+0x2c/0x68
>> add_memory_block+0x1b4/0x214
>> create_memory_block_devices+0x9c/0xfc
>> create_altmaps_and_memory_blocks+0x130/0x1cc
>> add_memory_resource+0x10c/0x21c
>> add_memory_driver_managed+0xb8/0xe8
>> virtio_mem_add_memory+0xa4/0x194 [virtio_mem]
>> virtio_mem_sbm_plug_and_add_mb+0xc8/0x16c [virtio_mem]
>> virtio_mem_run_wq+0xea8/0x1088 [virtio_mem]
>> process_scheduled_works+0x18c/0x300
>> worker_thread+0x1dc/0x2b8
>> kthread+0x1ac/0x1f4
>> ret_from_fork+0x10/0x20
>>
>> Fix this by delaying the assignment of mem->altmap until after
>> __add_memory_block() has succeeded.
>
> Something does not add up here. How do you get an altmap with virtio-mem?
That patch itself makes sense, but the callchain does not make sense.
virtio_mem does not set MHP_MEMMAP_ON_MEMORY, so it should never reach
create_altmaps_and_memory_blocks()?
--
Cheers,
David
next prev parent reply other threads:[~2026-05-13 13:20 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-13 13:09 [PATCH] drivers/base/memory: set mem->altmap after successful device registration Georgi Djakov
2026-05-13 13:14 ` David Hildenbrand (Arm)
2026-05-13 13:20 ` David Hildenbrand (Arm) [this message]
2026-05-13 16:01 ` Georgi Djakov
2026-05-13 16:07 ` David Hildenbrand (Arm)
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