Am 25.02.22 um 08:33 schrieb Daniel Vetter:

Useful for checking for dma-fence signalling annotations since they don't quite nest as freely as we'd like to.

Cc: Matthew Brost matthew.brost@intel.com Signed-off-by: Daniel Vetter daniel.vetter@intel.com Cc: Sumit Semwal sumit.semwal@linaro.org Cc: Gustavo Padovan gustavo@padovan.org Cc: "Christian König" christian.koenig@amd.com Cc: linux-media@vger.kernel.org Cc: linaro-mm-sig@lists.linaro.org

---

drivers/dma-buf/dma-fence.c | 19 +++++++++++++++++++ include/linux/dma-fence.h | 2 ++ 2 files changed, 21 insertions(+)

diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c index 066400ed8841..2b7c3fc965e6 100644 --- a/drivers/dma-buf/dma-fence.c +++ b/drivers/dma-buf/dma-fence.c @@ -307,6 +307,25 @@ bool dma_fence_begin_signalling(void) } EXPORT_SYMBOL(dma_fence_begin_signalling); +/**

• • dma_fence_assert_in_signalling_section - check fence signalling annotations
• • Since dma_fence_begin_signalling() and dma_fence_end_signalling() are built
• • using lockdep annotations they have limitations on how freely they can be
• • nested. Specifically, they cannot be on both inside and outside of locked
• • sections, which in practice means the annotations often have to be pushed out
• • to the top level callers.
• • To ensure low-level functions are only called with the correction
• • annotations, this function can be used to check for that.

I think I need a concrete example to understand what this is good for.

Christian.

• */

+void dma_fence_assert_in_signalling_section(void) +{

• if (!in_atomic())

• lockdep_assert(lock_is_held(&dma_fence_lockdep_map));
  

+} +EXPORT_SYMBOL(dma_fence_assert_in_signalling_section);

• /**
  • dma_fence_end_signalling - end a critical DMA fence signalling section
  • @cookie: opaque cookie from dma_fence_begin_signalling()

diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h index 775cdc0b4f24..7179a5692f72 100644 --- a/include/linux/dma-fence.h +++ b/include/linux/dma-fence.h @@ -356,6 +356,7 @@ dma_fence_get_rcu_safe(struct dma_fence __rcu **fencep) #ifdef CONFIG_LOCKDEP bool dma_fence_begin_signalling(void); +void dma_fence_assert_in_signalling_section(void); void dma_fence_end_signalling(bool cookie); void __dma_fence_might_wait(void); #else @@ -363,6 +364,7 @@ static inline bool dma_fence_begin_signalling(void) { return true; } +static inline void dma_fence_assert_in_signalling_section(void) {} static inline void dma_fence_end_signalling(bool cookie) {} static inline void __dma_fence_might_wait(void) {} #endif