Hi Hiroshi,
On Tuesday, August 21, 2012 2:15 PM Hiroshi Doyu wrote:
Hiroshi Doyu hdoyu@nvidia.com wrote @ Tue, 21 Aug 2012 13:22:35 +0200:
Hi,
On Mon, 30 Jul 2012 10:28:19 +0200 Marek Szyprowski m.szyprowski@samsung.com wrote:
This patch changes dma-mapping subsystem to use generic vmalloc areas for all consistent dma allocations. This increases the total size limit of the consistent allocations and removes platform hacks and a lot of duplicated code.
Atomic allocations are served from special pool preallocated on boot, because vmalloc areas cannot be reliably created in atomic context.
Signed-off-by: Marek Szyprowski m.szyprowski@samsung.com Reviewed-by: Kyungmin Park kyungmin.park@samsung.com
Documentation/kernel-parameters.txt | 2 +- arch/arm/include/asm/dma-mapping.h | 2 +- arch/arm/mm/dma-mapping.c | 486 ++++++++++++----------------------- arch/arm/mm/mm.h | 3 + include/linux/vmalloc.h | 1 + mm/vmalloc.c | 10 +- 6 files changed, 181 insertions(+), 323 deletions(-)
...
@@ -1117,61 +984,32 @@ static int __iommu_free_buffer(struct device *dev, struct page
**pages, size_t s
- Create a CPU mapping for a specified pages
*/ static void * -__iommu_alloc_remap(struct page **pages, size_t size, gfp_t gfp, pgprot_t prot) +__iommu_alloc_remap(struct page **pages, size_t size, gfp_t gfp, pgprot_t prot,
const void *caller){
struct arm_vmregion *c;size_t align;size_t count = size >> PAGE_SHIFT;int bit;
unsigned int i, nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;struct vm_struct *area;unsigned long p;
if (!consistent_pte[0]) {pr_err("%s: not initialised\n", __func__);dump_stack();
area = get_vm_area_caller(size, VM_ARM_DMA_CONSISTENT | VM_USERMAP,caller);if (!area)This patch replaced the custom "consistent_pte" with get_vm_area_caller()", which breaks the compatibility with the existing driver. This causes the following kernel oops(*1). That driver has called dma_pool_alloc() to allocate memory from the interrupt context, and it hits BUG_ON(in_interrpt()) in "get_vm_area_caller()"(*2). Regardless of the badness of allocation from interrupt handler in the driver, I have the following question.
The following "__get_vm_area_node()" can take gfp_mask, it means that this function is expected to be called from atomic context, but why it's _NOT_ allowed _ONLY_ from interrupt context?
According to the following definitions, "in_interrupt()" is in "in_atomic()".
#define in_interrupt() (preempt_count() & (HARDIRQ_MASK | SOFTIRQ_MASK | NMI_MASK)) #define in_atomic() ((preempt_count() & ~PREEMPT_ACTIVE) != 0)
Does anyone know why BUG_ON(in_interrupt()) is set in __get_vm_area_node(*3)?
For arm_dma_alloc(), it allocates from the pool if GFP_ATOMIC, but for arm_iommu_alloc_attrs() doesn't have pre-allocate pool at all, and it always call "get_vm_area_caller()". That's why it hits BUG(). But still I don't understand why it's not BUG_ON(in_atomic) as Russell already pointed out(*1).
Ok, now I see the problem. I will try to find out a solution for your issue.
Best regards