[PATCH kernel] powerpc/pseries/iommu: Add cond_resched() for huge updates

[Alexey Kardashevskiy <aik@ozlabs.ru>]

Mapping ~5.000.000 TCEs currently takes about 40s; this is the amount
required for a 300GB VM with 64k IOMMU page size. Anything bigger than
this produces RCU stall warnings.

This adds cond_resched() to allow the scheduler to do context switching
when it decides to.

This loop is called from dma_set_mask() which is a sleepable context.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
 arch/powerpc/platforms/pseries/iommu.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
index 889dc2e44b89..2b8de822272f 100644
--- a/arch/powerpc/platforms/pseries/iommu.c
+++ b/arch/powerpc/platforms/pseries/iommu.c
@@ -459,6 +459,7 @@ static int tce_setrange_multi_pSeriesLP(unsigned long start_pfn,
 static int tce_setrange_multi_pSeriesLP_walk(unsigned long start_pfn,
 		unsigned long num_pfn, void *arg)
 {
+	cond_resched();
 	return tce_setrange_multi_pSeriesLP(start_pfn, num_pfn, arg);
 }
 
-- 
2.17.1