Thread (2 messages) 2 messages, 2 authors, 2026-01-29

[PATCH v13] dma-buf: add some tracepoints to debug.

From: Xiang Gao <hidden>
Date: 2026-01-09 11:54:20
Also in: dri-devel, linux-media, lkml
Subsystem: dma buffer sharing framework, the rest, tracing · Maintainers: Sumit Semwal, Christian König, Linus Torvalds, Steven Rostedt, Masami Hiramatsu 

From: gaoxiang17 <redacted>

Since we can only inspect dmabuf by iterating over process FDs or the
dmabuf_list, we need to add our own tracepoints to track its status in
real time in production.

For example:
   binder:3016_1-3102    [006] ...1.   255.126521: dma_buf_export: exp_name=qcom,system size=12685312 ino=2738
   binder:3016_1-3102    [006] ...1.   255.126528: dma_buf_fd: exp_name=qcom,system size=12685312 ino=2738 fd=8
   binder:3016_1-3102    [006] ...1.   255.126642: dma_buf_mmap_internal: exp_name=qcom,system size=28672 ino=2739
     kworker/6:1-86      [006] ...1.   255.127194: dma_buf_put: exp_name=qcom,system size=12685312 ino=2738
    RenderThread-9293    [006] ...1.   316.618179: dma_buf_get: exp_name=qcom,system size=12771328 ino=2762 fd=176
    RenderThread-9293    [006] ...1.   316.618195: dma_buf_dynamic_attach: exp_name=qcom,system size=12771328 ino=2762 attachment:ffffff880a18dd00 is_dynamic=0 dev_name=kgsl-3d0
    RenderThread-9293    [006] ...1.   318.878220: dma_buf_detach: exp_name=qcom,system size=12771328 ino=2762 attachment:ffffff880a18dd00 is_dynamic=0 dev_name=kgsl-3d0

Signed-off-by: Xiang Gao <redacted>
---

Changes since v12: https://lore.kernel.org/all/20251229031547.59272-1-gxxa03070307@gmail.com/ (local)
- list history changes

Changes since v11: https://lore.kernel.org/all/20251225121119.2194228-1-gxxa03070307@gmail.com/ (local)
- Lined up the backslashes nicely for the macro DMA_BUF_TRACE.
- Used DEFINE_EVENT_CONDITION() to move the condition branch into the tracepoint.

Changes since v10: https://lore.kernel.org/all/20251224013455.1649879-1-gxxa03070307@gmail.com/ (local)
- Always expose dmabuf->name_lock if lockdep is enabled.

Changes since v9: https://lore.kernel.org/all/20251223032749.1371913-1-gxxa03070307@gmail.com/ (local)
- Fixed some whitespace issues with the macro DMA_BUF_TRACE again.

Changes since v8: https://lore.kernel.org/all/20251218062853.819744-1-gxxa03070307@gmail.com/ (local)
- Expose dmabuf->name_lock when lockdep is enabled but trace event is not.

Changes since v7: https://lore.kernel.org/all/20251217105132.643300-1-gxxa03070307@gmail.com/ (local)
- Fixed some whitespace issues with the macro DMA_BUF_TRACE.

Changes since v6: https://lore.kernel.org/all/20251216063952.516364-1-gxxa03070307@gmail.com/ (local)
- Add a comment for the macro DMA_BUF_TRACE.

Changes since v5: https://lore.kernel.org/all/20251201112148.843572-1-gxxa03070307@gmail.com/ (local)
- Add the macro DMA_BUF_TRACE.
- Modify the commit message.

Changes since v4: https://lore.kernel.org/all/20251128085215.550100-1-gxxa03070307@gmail.com/ (local)
- Remove the tracepoints exporting.
- Remove the file refcount for the trace.
- Print the dev_name last.
- Add the parameter of whether dma_buf attachment is dynamic.

Changes since v3: https://lore.kernel.org/all/20251127004352.376307-1-gxxa03070307@gmail.com/ (local)
- Take the dmabuf->name_lock around the tracepoint call itself.
- Used DECLARE_EVENT_CLASS() and a DEFINE_EVENT().

Changes since v2: https://lore.kernel.org/all/20251125162949.220488-1-gxxa03070307@gmail.com/ (local)
- Add more explanation to the commit message.

 drivers/dma-buf/dma-buf.c      |  9 ++----
 include/trace/events/dma_buf.h | 50 ++++++++++++++++++----------------
 2 files changed, 29 insertions(+), 30 deletions(-)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index a4d8f2ff94e4..ac4238063ec1 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -48,12 +48,10 @@
  */
 #define DMA_BUF_TRACE(FUNC, ...)					\
 	do {								\
-		if (FUNC##_enabled()) {					\
+		/* Always expose lock if lockdep is enabled */		\
+		if (IS_ENABLED(CONFIG_LOCKDEP) || FUNC##_enabled()) {	\
 			guard(spinlock)(&dmabuf->name_lock);		\
 			FUNC(__VA_ARGS__);				\
-		} else if (IS_ENABLED(CONFIG_LOCKDEP)) {		\
-			/* Expose this lock when lockdep is enabled */	\
-			guard(spinlock)(&dmabuf->name_lock);		\
 		}							\
 	} while (0)
 
@@ -806,8 +804,7 @@ int dma_buf_fd(struct dma_buf *dmabuf, int flags)
 		return -EINVAL;
 
 	fd = FD_ADD(flags, dmabuf->file);
-	if (fd >= 0)
-		DMA_BUF_TRACE(trace_dma_buf_fd, dmabuf, fd);
+	DMA_BUF_TRACE(trace_dma_buf_fd, dmabuf, fd);
 
 	return fd;
 }
diff --git a/include/trace/events/dma_buf.h b/include/trace/events/dma_buf.h
index 35f8140095f4..3bb88d05bcc8 100644
--- a/include/trace/events/dma_buf.h
+++ b/include/trace/events/dma_buf.h
@@ -15,15 +15,15 @@ DECLARE_EVENT_CLASS(dma_buf,
 	TP_ARGS(dmabuf),
 
 	TP_STRUCT__entry(
-		__string(exp_name, dmabuf->exp_name)
-		__field(size_t, size)
-		__field(ino_t, ino)
+		__string(	exp_name,		dmabuf->exp_name)
+		__field(	size_t,			size)
+		__field(	ino_t,			ino)
 	),
 
 	TP_fast_assign(
 		__assign_str(exp_name);
-		__entry->size = dmabuf->size;
-		__entry->ino = dmabuf->file->f_inode->i_ino;
+		__entry->size	= dmabuf->size;
+		__entry->ino	= dmabuf->file->f_inode->i_ino;
 	),
 
 	TP_printk("exp_name=%s size=%zu ino=%lu",
@@ -40,21 +40,21 @@ DECLARE_EVENT_CLASS(dma_buf_attach_dev,
 	TP_ARGS(dmabuf, attach, is_dynamic, dev),
 
 	TP_STRUCT__entry(
-		__string(dev_name, dev_name(dev))
-		__string(exp_name, dmabuf->exp_name)
-		__field(size_t, size)
-		__field(ino_t, ino)
-		__field(struct dma_buf_attachment *, attach)
-		__field(bool, is_dynamic)
+		__string(	dev_name,			dev_name(dev))
+		__string(	exp_name,			dmabuf->exp_name)
+		__field(	size_t,				size)
+		__field(	ino_t,				ino)
+		__field(	struct dma_buf_attachment *,	attach)
+		__field(	bool,				is_dynamic)
 	),
 
 	TP_fast_assign(
 		__assign_str(dev_name);
 		__assign_str(exp_name);
-		__entry->size = dmabuf->size;
-		__entry->ino = dmabuf->file->f_inode->i_ino;
-		__entry->is_dynamic = is_dynamic;
-		__entry->attach = attach;
+		__entry->size		= dmabuf->size;
+		__entry->ino		= dmabuf->file->f_inode->i_ino;
+		__entry->is_dynamic	= is_dynamic;
+		__entry->attach		= attach;
 	),
 
 	TP_printk("exp_name=%s size=%zu ino=%lu attachment:%p is_dynamic=%d dev_name=%s",
@@ -73,17 +73,17 @@ DECLARE_EVENT_CLASS(dma_buf_fd,
 	TP_ARGS(dmabuf, fd),
 
 	TP_STRUCT__entry(
-		__string(exp_name, dmabuf->exp_name)
-		__field(size_t, size)
-		__field(ino_t, ino)
-		__field(int, fd)
+		__string(	exp_name,		dmabuf->exp_name)
+		__field(	size_t,			size)
+		__field(	ino_t,			ino)
+		__field(	int,			fd)
 	),
 
 	TP_fast_assign(
 		__assign_str(exp_name);
-		__entry->size = dmabuf->size;
-		__entry->ino = dmabuf->file->f_inode->i_ino;
-		__entry->fd = fd;
+		__entry->size	= dmabuf->size;
+		__entry->ino	= dmabuf->file->f_inode->i_ino;
+		__entry->fd	= fd;
 	),
 
 	TP_printk("exp_name=%s size=%zu ino=%lu fd=%d",
@@ -137,11 +137,13 @@ DEFINE_EVENT(dma_buf_attach_dev, dma_buf_detach,
 	TP_ARGS(dmabuf, attach, is_dynamic, dev)
 );
 
-DEFINE_EVENT(dma_buf_fd, dma_buf_fd,
+DEFINE_EVENT_CONDITION(dma_buf_fd, dma_buf_fd,
 
 	TP_PROTO(struct dma_buf *dmabuf, int fd),
 
-	TP_ARGS(dmabuf, fd)
+	TP_ARGS(dmabuf, fd),
+
+	TP_CONDITION(fd >= 0)
 );
 
 DEFINE_EVENT(dma_buf_fd, dma_buf_get,
-- 
2.34.1
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