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Message-ID: <cec54e02-5e62-6a4e-60a1-4050d221e267@linux.intel.com>
Date: Wed, 19 Jun 2019 09:39:20 +0800
From: Lu Baolu <baolu.lu@...ux.intel.com>
To: Chris Wilson <chris@...is-wilson.co.uk>, dwmw2@...radead.org,
joro@...tes.org
Cc: baolu.lu@...ux.intel.com, ashok.raj@...el.com,
jacob.jun.pan@...ux.intel.com, Kevin Tian <kevin.tian@...el.com>,
iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
Dave Jiang <dave.jiang@...el.com>
Subject: Re: [PATCH 1/2] iommu/vt-d: Fix lock inversion between iommu->lock
and device_domain_lock
Hi Chris,
On 6/19/19 5:02 AM, Chris Wilson wrote:
> Quoting Lu Baolu (2019-05-21 08:30:15)
>> From: Dave Jiang <dave.jiang@...el.com>
>>
>> Lockdep debug reported lock inversion related with the iommu code
>> caused by dmar_insert_one_dev_info() grabbing the iommu->lock and
>> the device_domain_lock out of order versus the code path in
>> iommu_flush_dev_iotlb(). Expanding the scope of the iommu->lock and
>> reversing the order of lock acquisition fixes the issue.
>
> Which of course violates the property that device_domain_lock is the
> outer lock...
Agreed.
I also realized that this might be an incorrect fix. I am looking into
it and will submit a new fix later.
Best regards,
Lu Baolu
>
> <4>[ 1.252997] ======================================================
> <4>[ 1.252999] WARNING: possible circular locking dependency detected
> <4>[ 1.253002] 5.2.0-rc5-CI-CI_DRM_6299+ #1 Not tainted
> <4>[ 1.253004] ------------------------------------------------------
> <4>[ 1.253006] swapper/0/1 is trying to acquire lock:
> <4>[ 1.253009] 0000000091462475 (&(&iommu->lock)->rlock){+.+.}, at: domain_context_mapping_one+0xa0/0x4f0
> <4>[ 1.253015]
> but task is already holding lock:
> <4>[ 1.253017] 0000000069266737 (device_domain_lock){....}, at: domain_context_mapping_one+0x88/0x4f0
> <4>[ 1.253021]
> which lock already depends on the new lock.
>
> <4>[ 1.253024]
> the existing dependency chain (in reverse order) is:
> <4>[ 1.253027]
> -> #1 (device_domain_lock){....}:
> <4>[ 1.253031] _raw_spin_lock_irqsave+0x33/0x50
> <4>[ 1.253034] dmar_insert_one_dev_info+0xb8/0x520
> <4>[ 1.253036] set_domain_for_dev+0x66/0xf0
> <4>[ 1.253039] iommu_prepare_identity_map+0x48/0x95
> <4>[ 1.253042] intel_iommu_init+0xfd8/0x138d
> <4>[ 1.253045] pci_iommu_init+0x11/0x3a
> <4>[ 1.253048] do_one_initcall+0x58/0x300
> <4>[ 1.253051] kernel_init_freeable+0x2c0/0x359
> <4>[ 1.253054] kernel_init+0x5/0x100
> <4>[ 1.253056] ret_from_fork+0x3a/0x50
> <4>[ 1.253058]
> -> #0 (&(&iommu->lock)->rlock){+.+.}:
> <4>[ 1.253062] lock_acquire+0xa6/0x1c0
> <4>[ 1.253064] _raw_spin_lock+0x2a/0x40
> <4>[ 1.253067] domain_context_mapping_one+0xa0/0x4f0
> <4>[ 1.253070] pci_for_each_dma_alias+0x2b/0x160
> <4>[ 1.253072] dmar_insert_one_dev_info+0x44e/0x520
> <4>[ 1.253075] set_domain_for_dev+0x66/0xf0
> <4>[ 1.253077] iommu_prepare_identity_map+0x48/0x95
> <4>[ 1.253080] intel_iommu_init+0xfd8/0x138d
> <4>[ 1.253082] pci_iommu_init+0x11/0x3a
> <4>[ 1.253084] do_one_initcall+0x58/0x300
> <4>[ 1.253086] kernel_init_freeable+0x2c0/0x359
> <4>[ 1.253089] kernel_init+0x5/0x100
> <4>[ 1.253091] ret_from_fork+0x3a/0x50
> <4>[ 1.253093]
> other info that might help us debug this:
>
> <4>[ 1.253095] Possible unsafe locking scenario:
>
> <4>[ 1.253095] CPU0 CPU1
> <4>[ 1.253095] ---- ----
> <4>[ 1.253095] lock(device_domain_lock);
> <4>[ 1.253095] lock(&(&iommu->lock)->rlock);
> <4>[ 1.253095] lock(device_domain_lock);
> <4>[ 1.253095] lock(&(&iommu->lock)->rlock);
> <4>[ 1.253095]
> *** DEADLOCK ***
>
> <4>[ 1.253095] 2 locks held by swapper/0/1:
> <4>[ 1.253095] #0: 0000000076465a1e (dmar_global_lock){++++}, at: intel_iommu_init+0x1d3/0x138d
> <4>[ 1.253095] #1: 0000000069266737 (device_domain_lock){....}, at: domain_context_mapping_one+0x88/0x4f0
> <4>[ 1.253095]
> stack backtrace:
> <4>[ 1.253095] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.2.0-rc5-CI-CI_DRM_6299+ #1
> <4>[ 1.253095] Hardware name: /NUC5i7RYB, BIOS RYBDWi35.86A.0362.2017.0118.0940 01/18/2017
> <4>[ 1.253095] Call Trace:
> <4>[ 1.253095] dump_stack+0x67/0x9b
> <4>[ 1.253095] print_circular_bug+0x1c8/0x2b0
> <4>[ 1.253095] __lock_acquire+0x1ce9/0x24c0
> <4>[ 1.253095] ? lock_acquire+0xa6/0x1c0
> <4>[ 1.253095] lock_acquire+0xa6/0x1c0
> <4>[ 1.253095] ? domain_context_mapping_one+0xa0/0x4f0
> <4>[ 1.253095] _raw_spin_lock+0x2a/0x40
> <4>[ 1.253095] ? domain_context_mapping_one+0xa0/0x4f0
> <4>[ 1.253095] domain_context_mapping_one+0xa0/0x4f0
> <4>[ 1.253095] ? domain_context_mapping_one+0x4f0/0x4f0
> <4>[ 1.253095] pci_for_each_dma_alias+0x2b/0x160
> <4>[ 1.253095] dmar_insert_one_dev_info+0x44e/0x520
> <4>[ 1.253095] set_domain_for_dev+0x66/0xf0
> <4>[ 1.253095] iommu_prepare_identity_map+0x48/0x95
> <4>[ 1.253095] intel_iommu_init+0xfd8/0x138d
> <4>[ 1.253095] ? set_debug_rodata+0xc/0xc
> <4>[ 1.253095] ? set_debug_rodata+0xc/0xc
> <4>[ 1.253095] ? e820__memblock_setup+0x5b/0x5b
> <4>[ 1.253095] ? pci_iommu_init+0x11/0x3a
> <4>[ 1.253095] ? set_debug_rodata+0xc/0xc
> <4>[ 1.253095] pci_iommu_init+0x11/0x3a
> <4>[ 1.253095] do_one_initcall+0x58/0x300
> <4>[ 1.253095] kernel_init_freeable+0x2c0/0x359
> <4>[ 1.253095] ? rest_init+0x250/0x250
> <4>[ 1.253095] kernel_init+0x5/0x100
> <4>[ 1.253095] ret_from_fork+0x3a/0x50
>
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