| Message ID | 1349188056-4886-22-git-send-email-t.stanislaws@samsung.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Tomasz, Thanks for the patch. On Tuesday 02 October 2012 16:27:32 Tomasz Stanislawski wrote: > This patch adds taking reference to the device for MMAP buffers. > > Such buffers, may be exported using DMABUF mechanism. If the driver that > created a queue is unloaded then the queue is released, the device might be > released too. However, buffers cannot be released if they are referenced by > DMABUF descriptor(s). The device pointer kept in a buffer must be valid for > the whole buffer's lifetime. Therefore MMAP buffers should take a reference > to the device to avoid risk of dangling pointers. > > Signed-off-by: Tomasz Stanislawski <t.stanislaws@samsung.com> > > --- > drivers/media/video/videobuf2-dma-contig.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/drivers/media/video/videobuf2-dma-contig.c > b/drivers/media/video/videobuf2-dma-contig.c index b138b5c..b4d287a 100644 > --- a/drivers/media/video/videobuf2-dma-contig.c > +++ b/drivers/media/video/videobuf2-dma-contig.c > @@ -148,6 +148,7 @@ static void vb2_dc_put(void *buf_priv) > kfree(buf->sgt_base); > } > dma_free_coherent(buf->dev, buf->size, buf->vaddr, buf->dma_addr); > + put_device(buf->dev); > kfree(buf); > } > > @@ -161,9 +162,13 @@ static void *vb2_dc_alloc(void *alloc_ctx, unsigned > long size) if (!buf) > return ERR_PTR(-ENOMEM); > > + /* prevent the device from release while the buffer is exported */ > + get_device(dev); > + What about moving this below the dma_alloc_coherent() call ? You could then avoid the put_device() call in the error path. > buf->vaddr = dma_alloc_coherent(dev, size, &buf->dma_addr, GFP_KERNEL); > if (!buf->vaddr) { > dev_err(dev, "dma_alloc_coherent of size %ld failed\n", size); > + put_device(dev); > kfree(buf); > return ERR_PTR(-ENOMEM); > } Something like - buf->dev = dev; + buf->dev = get_device(dev); buf->size = size
diff --git a/drivers/media/video/videobuf2-dma-contig.c b/drivers/media/video/videobuf2-dma-contig.c index b138b5c..b4d287a 100644 --- a/drivers/media/video/videobuf2-dma-contig.c +++ b/drivers/media/video/videobuf2-dma-contig.c @@ -148,6 +148,7 @@ static void vb2_dc_put(void *buf_priv) kfree(buf->sgt_base); } dma_free_coherent(buf->dev, buf->size, buf->vaddr, buf->dma_addr); + put_device(buf->dev); kfree(buf); } @@ -161,9 +162,13 @@ static void *vb2_dc_alloc(void *alloc_ctx, unsigned long size) if (!buf) return ERR_PTR(-ENOMEM); + /* prevent the device from release while the buffer is exported */ + get_device(dev); + buf->vaddr = dma_alloc_coherent(dev, size, &buf->dma_addr, GFP_KERNEL); if (!buf->vaddr) { dev_err(dev, "dma_alloc_coherent of size %ld failed\n", size); + put_device(dev); kfree(buf); return ERR_PTR(-ENOMEM); }
This patch adds taking reference to the device for MMAP buffers. Such buffers, may be exported using DMABUF mechanism. If the driver that created a queue is unloaded then the queue is released, the device might be released too. However, buffers cannot be released if they are referenced by DMABUF descriptor(s). The device pointer kept in a buffer must be valid for the whole buffer's lifetime. Therefore MMAP buffers should take a reference to the device to avoid risk of dangling pointers. Signed-off-by: Tomasz Stanislawski <t.stanislaws@samsung.com> --- drivers/media/video/videobuf2-dma-contig.c | 5 +++++ 1 file changed, 5 insertions(+)