Re: [topic/core-for-CI] Revert "iommu/dma: Fix race condition during iova_domain initialization"
From: Robin Murphy
Date: Wed Sep 14 2022 - 11:54:52 EST
On 2022-09-14 16:01, Lucas De Marchi wrote:
On Wed, Sep 14, 2022 at 02:40:45PM +0200, Karolina Drobnik wrote:
This reverts commit ac9a5d522bb80be50ea84965699e1c8257d745ce.
This change introduces a regression on Alder Lake that completely
blocks testing. To enable CI and avoid possible circular locking
warning, revert the patch.
We are already on rc5. Are iommu authors involved aware of this issue?
We could do this in our "for CI only" branch, but it's equally important
that this is fixed for 6.0
Cc'ing them.
The lockdep report doesn't make much sense to me - the deadlock cycle
it's reporting doesn't even involve the mutex added by that commit, and
otherwise the lock ordering between the IOMMU bus notifier(s) and
cpu_hotplug_lock has existed for ages. Has lockdep somehow got multiple
different and unrelated bus notifiers mixed up, maybe?
FWIW nobody else has reported anything, and that mutex addresses a
real-world concurrency issue, so I'm not convinced a revert is
appropriate without at least a much clearer justification.
Robin.
thanks
Lucas De Marchi
kernel log:
======================================================
WARNING: possible circular locking dependency detected
6.0.0-rc5-CI_DRM_12132-g6c93e979e542+ #1 Not tainted
------------------------------------------------------
cpuhp/0/15 is trying to acquire lock:
ffff8881013df278 (&(&priv->bus_notifier)->rwsem){++++}-{3:3}, at:
blocking_notifier_call_chain+0x20/0x50
but task is already holding lock:
ffffffff826490c0 (cpuhp_state-up){+.+.}-{0:0}, at:
cpuhp_thread_fun+0x48/0x1f0
which lock already depends on the new loc
the existing dependency chain (in reverse order) is:
-> #3 (cpuhp_state-up){+.+.}-{0:0}:
lock_acquire+0xd3/0x310
cpuhp_thread_fun+0xa6/0x1f0
smpboot_thread_fn+0x1b5/0x260
kthread+0xed/0x120
ret_from_fork+0x1f/0x30
-> #2 (cpu_hotplug_lock){++++}-{0:0}:
lock_acquire+0xd3/0x310
__cpuhp_state_add_instance+0x43/0x1c0
iova_domain_init_rcaches+0x199/0x1c0
iommu_setup_dma_ops+0x130/0x440
bus_iommu_probe+0x26a/0x2d0
bus_set_iommu+0x82/0xd0
intel_iommu_init+0xe33/0x1039
pci_iommu_init+0x9/0x31
do_one_initcall+0x53/0x2f0
kernel_init_freeable+0x18f/0x1e1
kernel_init+0x11/0x120
ret_from_fork+0x1f/0x30
-> #1 (&domain->iova_cookie->mutex){+.+.}-{3:3}:
lock_acquire+0xd3/0x310
__mutex_lock+0x97/0xf10
iommu_setup_dma_ops+0xd7/0x440
iommu_probe_device+0xa4/0x180
iommu_bus_notifier+0x2d/0x40
notifier_call_chain+0x31/0x90
blocking_notifier_call_chain+0x3a/0x50
device_add+0x3c1/0x900
pci_device_add+0x255/0x580
pci_scan_single_device+0xa6/0xd0
pci_scan_slot+0x7a/0x1b0
pci_scan_child_bus_extend+0x35/0x2a0
vmd_probe+0x5cd/0x970
pci_device_probe+0x95/0x110
really_probe+0xd6/0x350
__driver_probe_device+0x73/0x170
driver_probe_device+0x1a/0x90
__driver_attach+0xbc/0x190
bus_for_each_dev+0x72/0xc0
bus_add_driver+0x1bb/0x210
driver_register+0x66/0xc0
do_one_initcall+0x53/0x2f0
kernel_init_freeable+0x18f/0x1e1
kernel_init+0x11/0x120
ret_from_fork+0x1f/0x30
-> #0 (&(&priv->bus_notifier)->rwsem){++++}-{3:3}:
validate_chain+0xb3f/0x2000
__lock_acquire+0x5a4/0xb70
lock_acquire+0xd3/0x310
down_read+0x39/0x140
blocking_notifier_call_chain+0x20/0x50
device_add+0x3c1/0x900
platform_device_add+0x108/0x240
coretemp_cpu_online+0xe1/0x15e [coretemp]
cpuhp_invoke_callback+0x181/0x8a0
cpuhp_thread_fun+0x188/0x1f0
smpboot_thread_fn+0x1b5/0x260
kthread+0xed/0x120
ret_from_fork+0x1f/0x30
other info that might help us debug thi
Chain exists of &(&priv->bus_notifier)->rwsem -->
cpu_hotplug_lock --> cpuhp_state-
Possible unsafe locking scenari
CPU0 CPU1
---- ----
lock(cpuhp_state-up);
lock(cpu_hotplug_lock);
lock(cpuhp_state-up);
lock(&(&priv->bus_notifier)->rwsem);
*** DEADLOCK *
2 locks held by cpuhp/0/15:
#0: ffffffff82648f10 (cpu_hotplug_lock){++++}-{0:0}, at:
cpuhp_thread_fun+0x48/0x1f0
#1: ffffffff826490c0 (cpuhp_state-up){+.+.}-{0:0}, at:
cpuhp_thread_fun+0x48/0x1f0
stack backtrace:
CPU: 0 PID: 15 Comm: cpuhp/0 Not tainted
6.0.0-rc5-CI_DRM_12132-g6c93e979e542+ #1
Hardware name: Intel Corporation Alder Lake Client
Platform/AlderLake-P DDR4 RVP, BIOS ADLPFWI1.R00.3135.A00.2203251419
03/25/2022
Call Trace:
<TASK>
dump_stack_lvl+0x56/0x7f
check_noncircular+0x132/0x150
validate_chain+0xb3f/0x2000
__lock_acquire+0x5a4/0xb70
lock_acquire+0xd3/0x310
? blocking_notifier_call_chain+0x20/0x50
down_read+0x39/0x140
? blocking_notifier_call_chain+0x20/0x50
blocking_notifier_call_chain+0x20/0x50
device_add+0x3c1/0x900
? dev_set_name+0x4e/0x70
platform_device_add+0x108/0x240
coretemp_cpu_online+0xe1/0x15e [coretemp]
? create_core_data+0x550/0x550 [coretemp]
cpuhp_invoke_callback+0x181/0x8a0
cpuhp_thread_fun+0x188/0x1f0
? smpboot_thread_fn+0x1e/0x260
smpboot_thread_fn+0x1b5/0x260
? sort_range+0x20/0x20
kthread+0xed/0x120
? kthread_complete_and_exit+0x20/0x20
ret_from_fork+0x1f/0x30
</TASK>
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/6641
Signed-off-by: Karolina Drobnik <karolina.drobnik@xxxxxxxxx>
Cc: Lucas De Marchi <lucas.demarchi@xxxxxxxxx>
---
drivers/iommu/dma-iommu.c | 17 ++++-------------
1 file changed, 4 insertions(+), 13 deletions(-)
diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 17dd683b2fce..9616b473e4c7 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -65,7 +65,6 @@ struct iommu_dma_cookie {
/* Domain for flush queue callback; NULL if flush queue not in use */
struct iommu_domain *fq_domain;
- struct mutex mutex;
};
static DEFINE_STATIC_KEY_FALSE(iommu_deferred_attach_enabled);
@@ -312,7 +311,6 @@ int iommu_get_dma_cookie(struct iommu_domain *domain)
if (!domain->iova_cookie)
return -ENOMEM;
- mutex_init(&domain->iova_cookie->mutex);
return 0;
}
@@ -563,33 +561,26 @@ static int iommu_dma_init_domain(struct
iommu_domain *domain, dma_addr_t base,
}
/* start_pfn is always nonzero for an already-initialised domain */
- mutex_lock(&cookie->mutex);
if (iovad->start_pfn) {
if (1UL << order != iovad->granule ||
base_pfn != iovad->start_pfn) {
pr_warn("Incompatible range for DMA domain\n");
- ret = -EFAULT;
- goto done_unlock;
+ return -EFAULT;
}
- ret = 0;
- goto done_unlock;
+ return 0;
}
init_iova_domain(iovad, 1UL << order, base_pfn);
ret = iova_domain_init_rcaches(iovad);
if (ret)
- goto done_unlock;
+ return ret;
/* If the FQ fails we can simply fall back to strict mode */
if (domain->type == IOMMU_DOMAIN_DMA_FQ && iommu_dma_init_fq(domain))
domain->type = IOMMU_DOMAIN_DMA;
- ret = iova_reserve_iommu_regions(dev, domain);
-
-done_unlock:
- mutex_unlock(&cookie->mutex);
- return ret;
+ return iova_reserve_iommu_regions(dev, domain);
}
/**
--
2.25.1