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Message-ID: <20251224093109.2fbbe3eb@gandalf.local.home>
Date: Wed, 24 Dec 2025 09:31:09 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Xiang Gao <gxxa03070307@...il.com>
Cc: sumit.semwal@...aro.org, christian.koenig@....com, mhiramat@...nel.org,
linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
linux-kernel@...r.kernel.org, mathieu.desnoyers@...icios.com,
dhowells@...hat.com, kuba@...nel.org, brauner@...nel.org,
akpm@...ux-foundation.org, linux-trace-kernel@...r.kernel.org, gaoxiang17
<gaoxiang17@...omi.com>
Subject: Re: [PATCH v10] dma-buf: add some tracepoints to debug.
On Wed, 24 Dec 2025 09:34:55 +0800
Xiang Gao <gxxa03070307@...il.com> wrote:
> From: gaoxiang17 <gaoxiang17@...omi.com>
>
> 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 <gaoxiang17@...omi.com>
> ---
BTW, it's sometimes nice to have in new versions of a patch with a list of
changes below the above "---" (here):
Changes since v9: https://lore.kernel.org/all/20251223032749.1371913-1-gxxa03070307@gmail.com/
- <list changes here>
That way it keeps a nice history of all the versions of the patch.
No need to resend. Just giving you some advice for future patches.
> drivers/dma-buf/dma-buf.c | 49 +++++++++-
> include/trace/events/dma_buf.h | 157 +++++++++++++++++++++++++++++++++
> 2 files changed, 204 insertions(+), 2 deletions(-)
> create mode 100644 include/trace/events/dma_buf.h
>
> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> index edaa9e4ee4ae..5e6f65cd0306 100644
> --- a/drivers/dma-buf/dma-buf.c
> +++ b/drivers/dma-buf/dma-buf.c
> @@ -35,6 +35,26 @@
>
> #include "dma-buf-sysfs-stats.h"
>
> +#define CREATE_TRACE_POINTS
> +#include <trace/events/dma_buf.h>
> +
> +/*
> + * dmabuf->name must be accessed with holding dmabuf->name_lock.
> + * we need to take the lock around the tracepoint call itself where
> + * it is called in the code.
> + *
> + * Note: FUNC##_enabled() is a static branch that will only
> + * be set when the trace event is enabled.
> + */
> +#define DMA_BUF_TRACE(FUNC, ...) \
> + do { \
> + /* Always expose lock if lockdep is enabled */ \
> + if (IS_ENABLED(CONFIG_LOCKDEP) || FUNC##_enabled()) { \
> + guard(spinlock)(&dmabuf->name_lock); \
> + FUNC(__VA_ARGS__); \
> + } \
> + } while (0)
I'm curious. Are the above backslashes lined up nicely in the code?
> +
> static inline int is_dma_buf_file(struct file *);
>
> static DEFINE_MUTEX(dmabuf_list_mutex);
> @@ -220,6 +240,8 @@ static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma)
> dmabuf->size >> PAGE_SHIFT)
> return -EINVAL;
>
> + DMA_BUF_TRACE(trace_dma_buf_mmap_internal, dmabuf);
> +
> return dmabuf->ops->mmap(dmabuf, vma);
> }
>
> @@ -745,6 +767,8 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info)
>
> __dma_buf_list_add(dmabuf);
>
> + DMA_BUF_TRACE(trace_dma_buf_export, dmabuf);
> +
> return dmabuf;
>
> err_dmabuf:
> @@ -768,10 +792,16 @@ EXPORT_SYMBOL_NS_GPL(dma_buf_export, "DMA_BUF");
> */
> int dma_buf_fd(struct dma_buf *dmabuf, int flags)
> {
> + int fd;
> +
> if (!dmabuf || !dmabuf->file)
> return -EINVAL;
>
> - return FD_ADD(flags, dmabuf->file);
> + fd = FD_ADD(flags, dmabuf->file);
> + if (fd >= 0)
> + DMA_BUF_TRACE(trace_dma_buf_fd, dmabuf, fd);
Instead of adding the above if statement in the code, you can make the
event conditional (See below). Then this could just be:
- return FD_ADD(flags, dmabuf->file);
+ fd = FD_ADD(flags, dmabuf->file);
+ DMA_BUF_TRACE(trace_dma_buf_fd, dmabuf, fd);
And not have the condition hit when tracing isn't enabled.
> +
> + return fd;
> }
> EXPORT_SYMBOL_NS_GPL(dma_buf_fd, "DMA_BUF");
>
[..]
> diff --git a/include/trace/events/dma_buf.h b/include/trace/events/dma_buf.h
> new file mode 100644
> index 000000000000..2c9ba8533467
> --- /dev/null
> +++ b/include/trace/events/dma_buf.h
> @@ -0,0 +1,157 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM dma_buf
> +
> +#if !defined(_TRACE_DMA_BUF_H) || defined(TRACE_HEADER_MULTI_READ)
> +#define _TRACE_DMA_BUF_H
> +
> +#include <linux/dma-buf.h>
> +#include <linux/tracepoint.h>
> +
> +DECLARE_EVENT_CLASS(dma_buf,
> +
> + TP_PROTO(struct dma_buf *dmabuf),
> +
> + TP_ARGS(dmabuf),
> +
> + TP_STRUCT__entry(
> + __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;
> + ),
> +
> + TP_printk("exp_name=%s size=%zu ino=%lu",
> + __get_str(exp_name),
> + __entry->size,
> + __entry->ino)
> +);
> +
> +DECLARE_EVENT_CLASS(dma_buf_attach_dev,
> +
> + TP_PROTO(struct dma_buf *dmabuf, struct dma_buf_attachment *attach,
> + bool is_dynamic, struct device *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)
> + ),
> +
> + 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;
> + ),
> +
> + TP_printk("exp_name=%s size=%zu ino=%lu attachment:%p is_dynamic=%d dev_name=%s",
> + __get_str(exp_name),
> + __entry->size,
> + __entry->ino,
> + __entry->attach,
> + __entry->is_dynamic,
> + __get_str(dev_name))
> +);
> +
> +DECLARE_EVENT_CLASS(dma_buf_fd,
> +
> + TP_PROTO(struct dma_buf *dmabuf, int 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)
> + ),
> +
> + TP_fast_assign(
> + __assign_str(exp_name);
> + __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",
> + __get_str(exp_name),
> + __entry->size,
> + __entry->ino,
> + __entry->fd)
> +);
> +
[..]
> +DEFINE_EVENT(dma_buf_fd, dma_buf_fd,
> +
> + TP_PROTO(struct dma_buf *dmabuf, int fd),
> +
> + TP_ARGS(dmabuf, fd)
> +);
If fd needs to be greater or equal to zero, you can make the above:
DEFINE_EVENT_CONDITION(dma_buf_fd, dma_buf_fd,
TP_PROTO(struct dma_buf *dmabuf, int fd),
TP_ARGS(dmabuf, fd),
TP_CONDITION(fd >= 0)
);
This places the "fd >= 0" into the code that is called when the tracepoint
is enabled. If the condition isn't met, then the tracepoint doesn't get
recorded.
-- Steve
> +
> +DEFINE_EVENT(dma_buf_fd, dma_buf_get,
> +
> + TP_PROTO(struct dma_buf *dmabuf, int fd),
> +
> + TP_ARGS(dmabuf, fd)
> +);
> +
> +#endif /* _TRACE_DMA_BUF_H */
> +
> +/* This part must be outside protection */
> +#include <trace/define_trace.h>
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