[Intel-gfx] [PATCH 08/13] dma-fence: cross-release annotations

[Daniel Vetter]

dma-fence is a completion on steriods, which also allows hardware to
directly sync work among each another. It's supposed to be deadlock
free, so let's try to make sure that holds at least for the cpu-only
interactions and waits.

It's a bit much #ifdef, but I figured for the single case it's not
worth it to pull it all out.

Also, the single global lockdep map is intentional: dma_fences are
supposed to be shared, we need all drivers to be compatible to each
another in their locking hierarchy.

v2:
- handle #idef mess cleaner
- also annotate dma_fence_signal()

v3:
- Add a dma_fence_might_wait() function to annotate fastpaths
- Put it all into headers for other code to use

Cc: Sumit Semwal <sumit.semwal at linaro.org>
Cc: Gustavo Padovan <gustavo at padovan.org>
Cc: linux-media at vger.kernel.org
Cc: linaro-mm-sig at lists.linaro.org
Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
---
 drivers/dma-buf/dma-fence.c | 14 ++++++++++++++
 include/linux/dma-fence.h   | 28 ++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+)

diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
index 1551ca7df394..7d56d8b48624 100644
--- a/drivers/dma-buf/dma-fence.c
+++ b/drivers/dma-buf/dma-fence.c
@@ -30,6 +30,13 @@
 EXPORT_TRACEPOINT_SYMBOL(dma_fence_emit);
 EXPORT_TRACEPOINT_SYMBOL(dma_fence_enable_signal);
 
+
+#ifdef CONFIG_LOCKDEP_CROSSRELEASE
+struct lockdep_map_cross dma_fence_wait_map =
+	STATIC_CROSS_LOCKDEP_MAP_INIT("dma_fence_signal", &dma_fence_wait_map);
+EXPORT_SYMBOL(dma_fence_wait_map);
+#endif
+
 /*
  * fence context counter: each execution context should have its own
  * fence context, this allows checking if fences belong to the same
@@ -106,6 +113,8 @@ int dma_fence_signal_locked(struct dma_fence *fence)
 
 	lockdep_assert_held(fence->lock);
 
+	dma_fence_wait_release_commit();
+
 	if (WARN_ON(!fence))
 		return -EINVAL;
 
@@ -153,6 +162,8 @@ int dma_fence_signal(struct dma_fence *fence)
 	if (test_and_set_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
 		return -EINVAL;
 
+	dma_fence_wait_release_commit();
+
 	fence->timestamp = ktime_get();
 	set_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT, &fence->flags);
 	trace_dma_fence_signaled(fence);
@@ -197,12 +208,15 @@ dma_fence_wait_timeout(struct dma_fence *fence, bool intr, signed long timeout)
 	if (WARN_ON(timeout < 0))
 		return -EINVAL;
 
+	dma_fence_wait_acquire();
 	trace_dma_fence_wait_start(fence);
 	if (fence->ops->wait)
 		ret = fence->ops->wait(fence, intr, timeout);
 	else
 		ret = dma_fence_default_wait(fence, intr, timeout);
 	trace_dma_fence_wait_end(fence);
+	dma_fence_wait_release();
+
 	return ret;
 }
 EXPORT_SYMBOL(dma_fence_wait_timeout);
diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
index 02dba8cd033d..8a045334a207 100644
--- a/include/linux/dma-fence.h
+++ b/include/linux/dma-fence.h
@@ -34,6 +34,34 @@ struct dma_fence;
 struct dma_fence_ops;
 struct dma_fence_cb;
 
+#ifdef CONFIG_LOCKDEP_CROSSRELEASE
+#include <linux/lockdep.h>
+extern struct lockdep_map_cross dma_fence_wait_map;
+
+static inline void dma_fence_wait_acquire(void)
+{
+	lock_acquire_exclusive(&dma_fence_wait_map.map, 0, 0, NULL, _RET_IP_);
+}
+static inline void dma_fence_wait_release(void)
+{
+	lock_release(&dma_fence_wait_map.map, 0, _RET_IP_);
+}
+static inline void dma_fence_wait_release_commit(void)
+{
+	lock_commit_crosslock(&dma_fence_wait_map.map);
+}
+#else
+static inline void dma_fence_wait_acquire(void) {}
+static inline void dma_fence_wait_release(void) {}
+static inline void dma_fence_wait_release_commit(void) {}
+#endif
+
+static inline void dma_fence_might_wait(void)
+{
+	dma_fence_wait_acquire();
+	dma_fence_wait_release();
+}
+
 /**
  * struct dma_fence - software synchronization primitive
  * @refcount: refcount for this fence
-- 
2.19.1