On Thu, Jan 21, 2021 at 11:56 PM Sumit Semwal <sumit.sem...@linaro.org> wrote:
>
> Hi John, Suren,
>
>
> On Wed, 20 Jan 2021 at 02:15, John Stultz <john.stu...@linaro.org> wrote:
> >
> > We shouldn't vunmap more then we vmap, but if we do, make
> > sure we complain loudly.
>
> I was checking the general usage of vunmap in the kernel, and I
> couldn't find many instances where we need to WARN_ON for the vunmap
> count more than vmap count. Is there a specific need for this in the heaps?
Hi Sumit,
My worry was that buffer->vmap_cnt could silently go negative. But if
this warning is not consistent with other places we do refcounted
vmap/vunmap then feel free to ignore my suggestion.
Thanks!
>
> Best,
> Sumit.
> >
> > Cc: Sumit Semwal <sumit.sem...@linaro.org>
> > Cc: Liam Mark <lm...@codeaurora.org>
> > Cc: Laura Abbott <labb...@kernel.org>
> > Cc: Brian Starkey <brian.star...@arm.com>
> > Cc: Hridya Valsaraju <hri...@google.com>
> > Cc: Suren Baghdasaryan <sur...@google.com>
> > Cc: Sandeep Patil <sspa...@google.com>
> > Cc: Daniel Mentz <danielme...@google.com>
> > Cc: Chris Goldsworthy <cgold...@codeaurora.org>
> > Cc: Ørjan Eide <orjan.e...@arm.com>
> > Cc: Robin Murphy <robin.mur...@arm.com>
> > Cc: Ezequiel Garcia <ezequ...@collabora.com>
> > Cc: Simon Ser <cont...@emersion.fr>
> > Cc: James Jones <jajo...@nvidia.com>
> > Cc: linux-me...@vger.kernel.org
> > Cc: dri-devel@lists.freedesktop.org
> > Suggested-by: Suren Baghdasaryan <sur...@google.com>
> > Signed-off-by: John Stultz <john.stu...@linaro.org>
> > ---
> > drivers/dma-buf/heaps/cma_heap.c | 1 +
> > drivers/dma-buf/heaps/system_heap.c | 1 +
> > 2 files changed, 2 insertions(+)
> >
> > diff --git a/drivers/dma-buf/heaps/cma_heap.c
> > b/drivers/dma-buf/heaps/cma_heap.c
> > index 364fc2f3e499..0c76cbc3fb11 100644
> > --- a/drivers/dma-buf/heaps/cma_heap.c
> > +++ b/drivers/dma-buf/heaps/cma_heap.c
> > @@ -232,6 +232,7 @@ static void cma_heap_vunmap(struct dma_buf *dmabuf,
> > struct dma_buf_map *map)
> > struct cma_heap_buffer *buffer = dmabuf->priv;
> >
> > mutex_lock(&buffer->lock);
> > + WARN_ON(buffer->vmap_cnt == 0);
> > if (!--buffer->vmap_cnt) {
> > vunmap(buffer->vaddr);
> > buffer->vaddr = NULL;
> > diff --git a/drivers/dma-buf/heaps/system_heap.c
> > b/drivers/dma-buf/heaps/system_heap.c
> > index 405351aad2a8..2321c91891f6 100644
> > --- a/drivers/dma-buf/heaps/system_heap.c
> > +++ b/drivers/dma-buf/heaps/system_heap.c
> > @@ -273,6 +273,7 @@ static void system_heap_vunmap(struct dma_buf *dmabuf,
> > struct dma_buf_map *map)
> > struct system_heap_buffer *buffer = dmabuf->priv;
> >
> > mutex_lock(&buffer->lock);
> > + WARN_ON(buffer->vmap_cnt == 0);
> > if (!--buffer->vmap_cnt) {
> > vunmap(buffer->vaddr);
> > buffer->vaddr = NULL;
> > --
> > 2.17.1
> >
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