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iommu/tegra241-cmdqv: do not use smp_processor_id in preemptible context

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During boot some of the calls to tegra241_cmdqv_get_cmdq() will happen
in preemptible context. As this function calls smp_processor_id(), if
CONFIG_DEBUG_PREEMPT is enabled, these calls will trigger a series of
"BUG: using smp_processor_id() in preemptible" backtraces.

As tegra241_cmdqv_get_cmdq() only calls smp_processor_id() to use the
CPU number as a factor to balance out traffic on cmdq usage, it is safe
to use raw_smp_processor_id() here.

Cc: <stable@vger.kernel.org>
Fixes: 918eb5c856f6 ("iommu/arm-smmu-v3: Add in-kernel support for NVIDIA Tegra241 (Grace) CMDQV")
Change-Id: I170a6c2f6846d75228750bca5ecd8e5efd90f231
Signed-off-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Link: https://lore.kernel.org/r/Z1L1mja3nXzsJ0Pk@uudg.org
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Ashish Mhetre <amhetre@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/c/3rdparty/canonical/linux-noble/+/3435445
GVS: buildbot_gerritrpt <buildbot_gerritrpt@nvidia.com>
Reviewed-by: Pritesh Raithatha <praithatha@nvidia.com>
This commit is contained in:
Luis Claudio R. Goncalves
2024-12-06 10:01:14 -03:00
committed by Ashish Mhetre
parent f0d493630e
commit 6e8b7fa767
1 changed files with 1 additions and 1 deletions
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2
drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c
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@@ -339,7 +339,7 @@ tegra241_cmdqv_get_cmdq(struct arm_smmu_device *smmu,
* one CPU at a time can enter the process, while the others
* will be spinning at the same lock.
*/
lidx = smp_processor_id() % cmdqv->num_lvcmdqs_per_vintf;
lidx = raw_smp_processor_id() % cmdqv->num_lvcmdqs_per_vintf;
vcmdq = vintf->lvcmdqs[lidx];
if (!vcmdq || !READ_ONCE(vcmdq->enabled))
return NULL;