Re: [PATCH] drm/nouveau: gk20a: Turn instmem lock into mutex

[Alexandre Courbot <acourbot@nvidia.com>]

On 02/24/2017 01:20 AM, Thierry Reding wrote:
> * PGP Signed by an unknown key
>
> On Mon, Jan 30, 2017 at 09:03:07PM +0100, Thierry Reding wrote:
>> From: Thierry Reding <treding@nvidia.com>
>>
>> The gk20a implementation of instance memory uses vmap()/vunmap() to map
>> memory regions into the kernel's virtual address space. These functions
>> may sleep, so protecting them by a spin lock is not safe. This triggers
>> a warning if the DEBUG_ATOMIC_SLEEP Kconfig option is enabled. Fix this
>> by using a mutex instead.
>>
>> Signed-off-by: Thierry Reding <treding@nvidia.com>
>> ---
>>  drivers/gpu/drm/nouveau/nvkm/subdev/instmem/gk20a.c | 19 ++++++++-----------
>>  1 file changed, 8 insertions(+), 11 deletions(-)
>
> Alex, could you take a look at this?

Sorry! Yes, using a mutex here should be safe since vmap() can sleep 
anyway. And I don't think this code can ever be reached in atomic 
context (Ben can confirm that last point). Tested this patch and it 
seems to work like a charm.

Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Tested-by: Alexandre Courbot <acourbot@nvidia.com>

>
> Thanks,
> Thierry
>
>> diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/instmem/gk20a.c b/drivers/gpu/drm/nouveau/nvkm/subdev/instmem/gk20a.c
>> index a6a7fa0d7679..7f5244d57d2f 100644
>> --- a/drivers/gpu/drm/nouveau/nvkm/subdev/instmem/gk20a.c
>> +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/instmem/gk20a.c
>> @@ -94,7 +94,7 @@ struct gk20a_instmem {
>>  	struct nvkm_instmem base;
>>
>>  	/* protects vaddr_* and gk20a_instobj::vaddr* */
>> -	spinlock_t lock;
>> +	struct mutex lock;
>>
>>  	/* CPU mappings LRU */
>>  	unsigned int vaddr_use;
>> @@ -184,11 +184,10 @@ gk20a_instobj_acquire_iommu(struct nvkm_memory *memory)
>>  	struct gk20a_instmem *imem = node->base.imem;
>>  	struct nvkm_ltc *ltc = imem->base.subdev.device->ltc;
>>  	const u64 size = nvkm_memory_size(memory);
>> -	unsigned long flags;
>>
>>  	nvkm_ltc_flush(ltc);
>>
>> -	spin_lock_irqsave(&imem->lock, flags);
>> +	mutex_lock(&imem->lock);
>>
>>  	if (node->base.vaddr) {
>>  		if (!node->use_cpt) {
>> @@ -216,7 +215,7 @@ gk20a_instobj_acquire_iommu(struct nvkm_memory *memory)
>>
>>  out:
>>  	node->use_cpt++;
>> -	spin_unlock_irqrestore(&imem->lock, flags);
>> +	mutex_unlock(&imem->lock);
>>
>>  	return node->base.vaddr;
>>  }
>> @@ -239,9 +238,8 @@ gk20a_instobj_release_iommu(struct nvkm_memory *memory)
>>  	struct gk20a_instobj_iommu *node = gk20a_instobj_iommu(memory);
>>  	struct gk20a_instmem *imem = node->base.imem;
>>  	struct nvkm_ltc *ltc = imem->base.subdev.device->ltc;
>> -	unsigned long flags;
>>
>> -	spin_lock_irqsave(&imem->lock, flags);
>> +	mutex_lock(&imem->lock);
>>
>>  	/* we should at least have one user to release... */
>>  	if (WARN_ON(node->use_cpt == 0))
>> @@ -252,7 +250,7 @@ gk20a_instobj_release_iommu(struct nvkm_memory *memory)
>>  		list_add_tail(&node->vaddr_node, &imem->vaddr_lru);
>>
>>  out:
>> -	spin_unlock_irqrestore(&imem->lock, flags);
>> +	mutex_unlock(&imem->lock);
>>
>>  	wmb();
>>  	nvkm_ltc_invalidate(ltc);
>> @@ -306,19 +304,18 @@ gk20a_instobj_dtor_iommu(struct nvkm_memory *memory)
>>  	struct gk20a_instmem *imem = node->base.imem;
>>  	struct device *dev = imem->base.subdev.device->dev;
>>  	struct nvkm_mm_node *r;
>> -	unsigned long flags;
>>  	int i;
>>
>>  	if (unlikely(list_empty(&node->base.mem.regions)))
>>  		goto out;
>>
>> -	spin_lock_irqsave(&imem->lock, flags);
>> +	mutex_lock(&imem->lock);
>>
>>  	/* vaddr has already been recycled */
>>  	if (node->base.vaddr)
>>  		gk20a_instobj_iommu_recycle_vaddr(node);
>>
>> -	spin_unlock_irqrestore(&imem->lock, flags);
>> +	mutex_unlock(&imem->lock);
>>
>>  	r = list_first_entry(&node->base.mem.regions, struct nvkm_mm_node,
>>  			     rl_entry);
>> @@ -580,7 +577,7 @@ gk20a_instmem_new(struct nvkm_device *device, int index,
>>  	if (!(imem = kzalloc(sizeof(*imem), GFP_KERNEL)))
>>  		return -ENOMEM;
>>  	nvkm_instmem_ctor(&gk20a_instmem, device, index, &imem->base);
>> -	spin_lock_init(&imem->lock);
>> +	mutex_init(&imem->lock);
>>  	*pimem = &imem->base;
>>
>>  	/* do not allow more than 1MB of CPU-mapped instmem */
>> --
>> 2.11.0
>>
>
> * Unknown Key
> * 0x7F3EB3A1
>

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