Regression on drm-tip

[Borah, Chaitanya Kumar]

Hello Lu,

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 drm-tip repository.

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<4>[    2.856622] WARNING: possible circular locking dependency detected
<4>[    2.856631] 6.14.0-rc5-CI_DRM_16217-gc55ef90b69d3+ #1 Tainted: G          I       
<4>[    2.856642] ------------------------------------------------------
<4>[    2.856650] swapper/0/1 is trying to acquire lock:
<4>[    2.856657] ffffffff8360ecc8 (iommu_probe_device_lock){+.+.}-{3:3}, at: iommu_probe_device+0x1d/0x70
<4>[    2.856679] 
                  but task is already holding lock:
<4>[    2.856686] ffff888102ab6fa8 (&device->physical_node_lock){+.+.}-{3:3}, at: intel_iommu_init+0xea1/0x1220
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Details log can be found in [2].

After bisecting the tree, the following patch [3] seems to be the first "bad" commit

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commit b150654f74bf0df8e6a7936d5ec51400d9ec06d8
Author: Lu Baolu mailto:baolu.lu at linux.intel.com
Date:   Fri Feb 28 18:27:26 2025 +0800

    iommu/vt-d: Fix suspicious RCU usage

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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?

Gitlab issue for the regression is [4].

Thank you.

Regards

Chaitanya

[1] https://intel-gfx-ci.01.org/tree/drm-tip/combined-alt.html?
[2] https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_16276/fi-kbl-8809g/boot0.txt
[3] https://cgit.freedesktop.org/drm-tip/commit/?id=b150654f74bf0df8e6a7936d5ec51400d9ec06d8
[4] https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/13818

Regards

Chaitanya