In order to debug latency issues, I wanted to use ftrace on my M54418
coldfire. Sadly, it is not supported yet.
Thanks to Steven [1] it does not sound too difficult.
This small series adds basic functions to make it work, and for the few
tests I could do, it seems to be working well.
Here is a simple output I get:
```
bash-232 [000] d..3. 947.629000: thread_noise: bash:232 start 947.629000000 duration 0 ns
timerlat/0-274 [000] ..... 947.629000: #51598 context thread timer_latency 409280 ns
bash-232 [000] d.h.. 947.630000: #51599 context irq timer_latency 110720 ns
bash-232 [000] dnh1. 947.630000: irq_noise: timer:206 start 947.629000000 duration 1000000 ns
bash-232 [000] d..3. 947.630000: thread_noise: bash:232 start 947.630000000 duration 0 ns
timerlat/0-274 [000] ..... 947.630000: #51599 context thread timer_latency 407168 ns
bash-232 [000] d.h.. 947.631000: #51600 context irq timer_latency 108608 ns
bash-232 [000] dnh1. 947.631000: irq_noise: timer:206 start 947.630000000 duration 1000000 ns
bash-232 [000] d..3. 947.631000: thread_noise: bash:232 start 947.631000000 duration 0 ns
timerlat/0-274 [000] ..... 947.631000: #51600 context thread timer_latency 401472 ns
```
I used this on my board and afaik, it works quite well.
```
telnetd-229 0Dnh4. 13us+: 229:120:R + [000] 118: 49:R irq/100-enet-fe
telnetd-229 0Dnh4. 53us+: <stack trace>
=> __trace_stack
=> probe_wakeup
=> try_to_wake_up
=> wake_up_process
=> __handle_irq_event_percpu
=> handle_irq_event
=> handle_level_irq
=> generic_handle_irq
=> do_IRQ
=> inthandler
=> ip_finish_output2
=> __ip_finish_output
=> ip_output
=> __ip_queue_xmit
=> ip_queue_xmit
=> __tcp_transmit_skb
=> tcp_write_xmit
=> __tcp_push_pending_frames
=> tcp_push
=> tcp_sendmsg_locked
=> tcp_sendmsg
=> inet_sendmsg
=> sock_write_iter
=> vfs_write
=> ksys_write
=> sys_write
=> system_call
telnetd-229 0Dnh4. 68us!: wake_up_process <-__handle_irq_event_percpu
telnetd-229 0D..3. 348us+: __schedule <-preempt_schedule_irq
telnetd-229 0D..3. 368us+: 229:120:R ==> [000] 118: 49:R irq/100-enet-fe
telnetd-229 0D..3. 395us : <stack trace>
=> __trace_stack
=> probe_wakeup_sched_switch
=> __schedule
=> preempt_schedule_irq
=> Lkernel_return
=> ip_finish_output2
=> __ip_finish_output
=> ip_output
=> __ip_queue_xmit
=> ip_queue_xmit
=> __tcp_transmit_skb
=> tcp_write_xmit
=> __tcp_push_pending_frames
=> tcp_push
=> tcp_sendmsg_locked
=> tcp_sendmsg
=> inet_sendmsg
=> sock_write_iter
=> vfs_write
=> ksys_write
=> sys_write
=> system_call
```
[1]: https://lore.kernel.org/linux-m68k/20241018124511.70d29198@xxxxxxxxxxxxxxxxxx
Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@xxxxxxxxxx>
---
Changes in v4:
- Take Steve's v1 remarks !
- Link to v3: https://lore.kernel.org/r/20241203-add-m68k-tracing-support-v3-0-4de93f6cae55@xxxxxxxxxx
Changes in v3:
- Do not unconditionaly select the frame pointers
- Link to v2: https://lore.kernel.org/r/20241203-add-m68k-tracing-support-v2-0-77302097a9f4@xxxxxxxxxx
Changes in v2:
- Use the frame pointer and declare it
- Comments on trace_irq have been tested, but adding the trace_on/off in
entry.S fails badly
- Link to v1: https://lore.kernel.org/r/20241021-add-m68k-tracing-support-v1-0-0883d704525b@xxxxxxxxxx
---
Jean-Michel Hautbois (2):
m68k: Enable traceirqs
arch: m68k: Add STACKTRACE support
arch/m68k/Kconfig | 6 ++++
arch/m68k/kernel/Makefile | 1 +
arch/m68k/kernel/stacktrace.c | 70 +++++++++++++++++++++++++++++++++++++++++++
3 files changed, 77 insertions(+)
---
base-commit: e70140ba0d2b1a30467d4af6bcfe761327b9ec95
change-id: 20241021-add-m68k-tracing-support-36c18d2233d8
Best regards,
--
Jean-Michel Hautbois <jeanmichel.hautbois@xxxxxxxxxx>
