dma-fance: Add dma_fence_assert_in_signalling_section
Commit Message
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(+)
Comments
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
@@ -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.
+ */
+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()
@@ -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