Re: [topic/core-for-CI] Revert "iommu/dma: Fix race condition during iova_domain initialization"
From: Karolina Drobnik
Date: Mon Sep 19 2022 - 10:02:11 EST
On 16.09.2022 22:32, Lucas De Marchi wrote:
On Fri, Sep 16, 2022 at 02:24:00PM +0200, Karolina Drobnik wrote:
On 14.09.2022 17:54, Robin Murphy wrote:
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.
I'll share more background on this regression. We've noticed that no
tests were run for Alder Lake platforms. This may happens when, for
example, there is a kernel taint or lockdep warning.
Links:
https://intel-gfx-ci.01.org/tree/drm-tip/bat-adlm-1.html
https://intel-gfx-ci.01.org/tree/drm-tip/bat-adlp-6.html
The CI logs (which can be found for example here[1], boot0 file)
revealed a lockdep warning. One of the recent changes in the area was
commit ac9a5d522bb8 ("iommu/dma: Fix race condition during iova_domain
initialization"), and I sent a revert patch to test it on CI[2]. This
proved to be effective, as the tests started running on Alder Lake
platform:
https://intel-gfx-ci.01.org/tree/drm-tip/Trybot_108474v1/index.html?hosts=adlp
To be clear, that revert is just a way of unblocking CI testing, the
problem requires a specific fix.
Lucas, would it be possible to merge this revert to the topic branch to
unblock Alder Lake until this issue is fixed? I'm afraid that some
regressions could slip through the cracks if we don't do it soon enough.
Yeah. Let's have CI running with the revertt so we can see if on next runs
it will really show it was a regression or if it's something else. I
think it will help us understand why it's failing.
Thanks for the merge. It looks like all adls are doing better now
(revert went in CI_DRM_12147):
https://intel-gfx-ci.01.org/tree/drm-tip/bat-adlp-6.html
https://intel-gfx-ci.01.org/tree/drm-tip/bat-adln-1.html
https://intel-gfx-ci.01.org/tree/drm-tip/bat-adlm-1.html (CI_DRM_12149
seems to show a different problem)
All the best,
Karolina
Lucas De Marchi
Thanks,
Karolina
----
[1] -
https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_12145/bat-adlm-1/igt@runner@xxxxxxxxxxxx
[2] - https://patchwork.freedesktop.org/series/108474/
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