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

[Ben Skeggs]

On 02/24/2017 05:25 PM, Alexandre Courbot wrote:
> 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 at 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 at 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.
That should be true on this chipset.  Though, if we ever need to touch
the grctx or something in response to an interrupt (iirc nvgpu does
this, maybe?), this could change.  Granted, we probably should switch to
threaded interrupts at some point anyway.

As it currently stands, it should be fine.

Ben.

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