Commit 1f806218 authored by Luis Claudio R. Goncalves's avatar Luis Claudio R. Goncalves Committed by Will Deacon
Browse files

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



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: 918eb5c8 ("iommu/arm-smmu-v3: Add in-kernel support for NVIDIA Tegra241 (Grace) CMDQV")
Signed-off-by: default avatarLuis Claudio R. Goncalves <lgoncalv@redhat.com>
Reviewed-by: default avatarJason Gunthorpe <jgg@nvidia.com>
Reviewed-by: default avatarNicolin Chen <nicolinc@nvidia.com>
Tested-by: default avatarNicolin Chen <nicolinc@nvidia.com>
Link: https://lore.kernel.org/r/Z1L1mja3nXzsJ0Pk@uudg.org


Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent fac04efc

drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c

+1 −1
Original line number Diff line number Diff line
@@ -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;