| Message ID | 20230529223935.2672495-3-dmitry.osipenko@collabora.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Move dma-buf mmap() reservation locking down to exporters | expand |
On Mon, May 29, 2023 at 3:46 PM Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote: > > Don't assert held dma-buf reservation lock on memory mapping of exported > buffer. > > We're going to change dma-buf mmap() locking policy such that exporters > will have to handle the lock. The previous locking policy caused deadlock > problem for DRM drivers in a case of self-imported dma-bufs once these > drivers are moved to use reservation lock universally. The problem > solved by moving the lock down to exporters. This patch prepares dma-buf > heaps for the locking policy update. > Hi Dmitry, I see that in patch 6 of this series calls to dma_resv_lock/dma_resv_unlock have been added to the drm_gem_shmem_helper functions and some exporters. But I'm curious why no dma_resv_lock/dma_resv_unlock calls were added to these two dma-buf heap exporters for mmap? Thanks, T.J. > Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com> > Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com> > --- > drivers/dma-buf/heaps/cma_heap.c | 3 --- > drivers/dma-buf/heaps/system_heap.c | 3 --- > 2 files changed, 6 deletions(-) > > diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c > index 1131fb943992..28fb04eccdd0 100644 > --- a/drivers/dma-buf/heaps/cma_heap.c > +++ b/drivers/dma-buf/heaps/cma_heap.c > @@ -13,7 +13,6 @@ > #include <linux/dma-buf.h> > #include <linux/dma-heap.h> > #include <linux/dma-map-ops.h> > -#include <linux/dma-resv.h> > #include <linux/err.h> > #include <linux/highmem.h> > #include <linux/io.h> > @@ -183,8 +182,6 @@ static int cma_heap_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma) > { > struct cma_heap_buffer *buffer = dmabuf->priv; > > - dma_resv_assert_held(dmabuf->resv); > - > if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0) > return -EINVAL; > > diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c > index e8bd10e60998..fcf836ba9c1f 100644 > --- a/drivers/dma-buf/heaps/system_heap.c > +++ b/drivers/dma-buf/heaps/system_heap.c > @@ -13,7 +13,6 @@ > #include <linux/dma-buf.h> > #include <linux/dma-mapping.h> > #include <linux/dma-heap.h> > -#include <linux/dma-resv.h> > #include <linux/err.h> > #include <linux/highmem.h> > #include <linux/mm.h> > @@ -202,8 +201,6 @@ static int system_heap_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma) > struct sg_page_iter piter; > int ret; > > - dma_resv_assert_held(dmabuf->resv); > - > for_each_sgtable_page(table, &piter, vma->vm_pgoff) { > struct page *page = sg_page_iter_page(&piter); > > -- > 2.40.1 >
Hi, On 6/21/23 20:21, T.J. Mercier wrote: > On Mon, May 29, 2023 at 3:46 PM Dmitry Osipenko > <dmitry.osipenko@collabora.com> wrote: >> >> Don't assert held dma-buf reservation lock on memory mapping of exported >> buffer. >> >> We're going to change dma-buf mmap() locking policy such that exporters >> will have to handle the lock. The previous locking policy caused deadlock >> problem for DRM drivers in a case of self-imported dma-bufs once these >> drivers are moved to use reservation lock universally. The problem >> solved by moving the lock down to exporters. This patch prepares dma-buf >> heaps for the locking policy update. >> > Hi Dmitry, > > I see that in patch 6 of this series calls to > dma_resv_lock/dma_resv_unlock have been added to the > drm_gem_shmem_helper functions and some exporters. But I'm curious why > no dma_resv_lock/dma_resv_unlock calls were added to these two dma-buf > heap exporters for mmap? DMA-buf heaps are exporters, drm_gem_shmem_helper is importer. Locking rules are different for importers and exporters. DMA-heaps use own locking, they can be moved to resv lock in the future. DMA-heaps don't protect internal data in theirs mmap() implementations, nothing to protect there.
On Wed, Jun 21, 2023 at 11:16 AM Dmitry Osipenko <dmitry.osipenko@collabora.com> wrote: > > Hi, > > On 6/21/23 20:21, T.J. Mercier wrote: > > On Mon, May 29, 2023 at 3:46 PM Dmitry Osipenko > > <dmitry.osipenko@collabora.com> wrote: > >> > >> Don't assert held dma-buf reservation lock on memory mapping of exported > >> buffer. > >> > >> We're going to change dma-buf mmap() locking policy such that exporters > >> will have to handle the lock. The previous locking policy caused deadlock > >> problem for DRM drivers in a case of self-imported dma-bufs once these > >> drivers are moved to use reservation lock universally. The problem > >> solved by moving the lock down to exporters. This patch prepares dma-buf > >> heaps for the locking policy update. > >> > > Hi Dmitry, > > > > I see that in patch 6 of this series calls to > > dma_resv_lock/dma_resv_unlock have been added to the > > drm_gem_shmem_helper functions and some exporters. But I'm curious why > > no dma_resv_lock/dma_resv_unlock calls were added to these two dma-buf > > heap exporters for mmap? > > DMA-buf heaps are exporters, drm_gem_shmem_helper is importer. Locking > rules are different for importers and exporters. > > DMA-heaps use own locking, they can be moved to resv lock in the future. > > DMA-heaps don't protect internal data in theirs mmap() implementations, > nothing to protect there. > Thanks.
diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c index 1131fb943992..28fb04eccdd0 100644 --- a/drivers/dma-buf/heaps/cma_heap.c +++ b/drivers/dma-buf/heaps/cma_heap.c @@ -13,7 +13,6 @@ #include <linux/dma-buf.h> #include <linux/dma-heap.h> #include <linux/dma-map-ops.h> -#include <linux/dma-resv.h> #include <linux/err.h> #include <linux/highmem.h> #include <linux/io.h> @@ -183,8 +182,6 @@ static int cma_heap_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma) { struct cma_heap_buffer *buffer = dmabuf->priv; - dma_resv_assert_held(dmabuf->resv); - if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0) return -EINVAL; diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c index e8bd10e60998..fcf836ba9c1f 100644 --- a/drivers/dma-buf/heaps/system_heap.c +++ b/drivers/dma-buf/heaps/system_heap.c @@ -13,7 +13,6 @@ #include <linux/dma-buf.h> #include <linux/dma-mapping.h> #include <linux/dma-heap.h> -#include <linux/dma-resv.h> #include <linux/err.h> #include <linux/highmem.h> #include <linux/mm.h> @@ -202,8 +201,6 @@ static int system_heap_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma) struct sg_page_iter piter; int ret; - dma_resv_assert_held(dmabuf->resv); - for_each_sgtable_page(table, &piter, vma->vm_pgoff) { struct page *page = sg_page_iter_page(&piter);