Messages in this thread | | | From | Suren Baghdasaryan <> | Date | Fri, 22 Jan 2021 14:20:56 -0800 | Subject | Re: [RESEND][PATCH 2/3] dma-buf: heaps: Add a WARN_ON should the vmap_cnt go negative |
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On Thu, Jan 21, 2021 at 11:56 PM Sumit Semwal <sumit.semwal@linaro.org> wrote: > > Hi John, Suren, > > > On Wed, 20 Jan 2021 at 02:15, John Stultz <john.stultz@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.semwal@linaro.org> > > Cc: Liam Mark <lmark@codeaurora.org> > > Cc: Laura Abbott <labbott@kernel.org> > > Cc: Brian Starkey <Brian.Starkey@arm.com> > > Cc: Hridya Valsaraju <hridya@google.com> > > Cc: Suren Baghdasaryan <surenb@google.com> > > Cc: Sandeep Patil <sspatil@google.com> > > Cc: Daniel Mentz <danielmentz@google.com> > > Cc: Chris Goldsworthy <cgoldswo@codeaurora.org> > > Cc: Ørjan Eide <orjan.eide@arm.com> > > Cc: Robin Murphy <robin.murphy@arm.com> > > Cc: Ezequiel Garcia <ezequiel@collabora.com> > > Cc: Simon Ser <contact@emersion.fr> > > Cc: James Jones <jajones@nvidia.com> > > Cc: linux-media@vger.kernel.org > > Cc: dri-devel@lists.freedesktop.org > > Suggested-by: Suren Baghdasaryan <surenb@google.com> > > Signed-off-by: John Stultz <john.stultz@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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