# Re: \[PATCH v8 2/5\] tracing: Use the stackmap from the ftrace stack recording path

- From: Pengfei Li \<hidden\>
- Date: 2026-11-08 07:25:10 
- List: linux-trace-kernel
- Page: https://ratatoskr.run/linux-trace-kernel/2026/11/17891640
- Thread: https://ratatoskr.run/oe-kbuild-all/2026/11/17891010/t.md

```text
On Sun, 08 Nov 2026 06:35:01 +0800, kernel test robot wrote:
> kernel/trace/trace.c: In function 'record_stackmap':
> include/linux/rcupdate.h:502:9: error: dereferencing pointer to incomplete type 'struct ftrace_stackmap'

struct ftrace_stackmap is only defined in trace_stackmap.c, and GCC
before 10 rejects typeof(*p) on the incomplete type in
rcu_dereference_sched(). I reproduced it with GCC 8.5.

v9 will move the rcu_dereference_sched() into
ftrace_stackmap_get_cookie(), which will take the trace_array instead
of the map.

-- Pengfei
```