Hello Julian,
Hope you are doing well. I am Chaitanya from the linux graphics team in
Intel.
This mail is regarding a regression we are seeing in our CI runs[1] on
linux-next repository.
Since the version next-20250814 [2], we are seeing the following regression
`````````````````````````````````````````````````````````````````````````````````
<4>[ 25.645493] ======================================================
<4>[ 25.645497] WARNING: possible circular locking dependency detected
<5>[ 25.645501] 6.17.0-rc2-next-20250818-next-20250818-g3ac864c2d9bb+
#1 Not tainted
<4>[ 25.645506] ------------------------------------------------------
<4>[ 25.645509] swapper/0/1 is trying to acquire lock:
<5>[ 25.645513] ffffffff83488270 (cpu_hotplug_lock){++++}-{0:0}, at:
static_key_slow_inc+0x12/0x30
<4>[ 25.645526]
but task is already holding lock:
<5>[ 25.645529] ffff8881063fce30
(&q->q_usage_counter(io)){++++}-{0:0}, at:
blk_mq_freeze_queue_nomemsave+0x12/0x30
<4>[ 25.645540]
which lock already depends on the new lock.
<4>[ 25.645545]
the existing dependency chain (in reverse order) is:
<5>[ 25.645549]
-> #2 (&q->q_usage_counter(io)){++++}-{0:0}:
<5>[ 25.645554] blk_alloc_queue+0x324/0x360
<5>[ 25.645560] blk_mq_alloc_queue+0x6a/0xe0
<5>[ 25.645564] __blk_mq_alloc_disk+0x19/0x70
<5>[ 25.645567] loop_add+0x240/0x430
<5>[ 25.645573] loop_init+0xcd/0x190
<5>[ 25.645576] do_one_initcall+0x5d/0x3f0
<5>[ 25.645581] kernel_init_freeable+0x3cd/0x6a0
<5>[ 25.645586] kernel_init+0x1b/0x200
<5>[ 25.645591] ret_from_fork+0x26c/0x2e0
<5>[ 25.645597] ret_from_fork_asm+0x1a/0x30
`````````````````````````````````````````````````````````````````````````````````
Details log can be found in [3].
After bisecting the tree, the following patch [4] seems to be the first
"bad" commit
`````````````````````````````````````````````````````````````````````````````````````````````````````````
commit 8f5845e0743bf3512b71b3cb8afe06c192d6acc4
Author: Julian Sun sunjunchao2870@xxxxxxxxx
Date: Tue Aug 12 23:42:57 2025 +0800
block: restore default wbt enablement
`````````````````````````````````````````````````````````````````````````````````````````````````````````
We also verified that if we revert the patch the issue is not seen.
Could you please check why the patch causes this regression and provide
a fix if necessary?
Thank you.
Regards
Chaitanya
[1]
https://intel-gfx-ci.01.org/tree/linux-next/combined-alt.html?
[2]
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?h=next-20250814
[3]
https://intel-gfx-ci.01.org/tree/linux-next/next-20250818/bat-twl-1/boot0.txt
[4]
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?h=next-20250818&id=8f5845e0743bf3512b71b3cb8afe06c192d6acc4
