[GDB] Debugger seems to crash when stepping inside an IRQ handler

[lutrampal]

Hello there,

Describe the bug
When setting a breakpoint inside an IRQ handler in my application, I'm experiencing the following crash each time I try to continue, step over, step into or step out of the handler:

/__w/_temp/workspace/build/.build/arm-zephyr-eabi/src/gdb/gdb/infrun.c:5825: internal-error: finish_step_over: Assertion `ecs->event_thread->control.trap_expected' failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.

Quit this debugging session?
(y or n) [answered Y; input not from terminal]

This is a bug, please report it.
  For instructions, see:
<github.com/.../issues>.

/__w/_temp/workspace/build/.build/arm-zephyr-eabi/src/gdb/gdb/infrun.c:5825: internal-error: finish_step_over: Assertion `ecs->event_thread->control.trap_expected' failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.

Create a core file of GDB?
(y or n) [answered Y; input not from terminal]
GDB session ended unexpectedly. exit-code: none, signal: SIGABRT

Here's the GDB coredump: core.zip

Please also mention any information which could help others to understand
the problem you're facing
- Target CPU: NRF5340 Application core
- Zephyr SDK revision: 0.16.4 (gdb v12.1)
- Zephyr OS revision: v3.4.99-ncs1-1 (Nordic's current fork revision on NRF SDK v2.5.1)
- Debugging probe: SEGGER JLink BASE Compact with J-Link GDB Server V7.94f (latest)
- I'm in the process of updating the NRF SDK and I did not encounter this issue in the previous version used in my project (v2.4.1). I'm also reporting this crash as a Zephyr SDK issue in case this should be handled by the Zephyr team.

Steps to reproduce
1. Set a breakpoint inside an IRQ handler
2. Have your code hit the breakpoint
3. Try to step to next instruction after the breakpoint
=> GDB crashes with the reported error
NB: I was able to consistently reproduce the crash on my setup by setting a breakpoint in several distinct IRQ handlers. The crash does not occur when debugging regular code which is why I deduced that the issue is somehow linked to IRQ handlers.

Expected behaviour
Stepping inside function should not crash GDB.

[Susheel Nuguru]

Do you think that this is is the issue with the nRF solution or in GDB in general?

Have you tried to use any other debugger than gdb session? Try using the VSC extension or Segger ozone and see if you see the same. 

- I'm in the process of updating the NRF SDK and I did not encounter this issue in the previous version used in my project (v2.4.1). I'm also reporting this crash as a Zephyr SDK issue in case this should be handled by the Zephyr team.

This is interesting, something broke somewhere. But I can help you try to get solution for this once we know that this is only gdb specific or issue in general with any debugger.

[lutrampal]

Hi Susheel and thank you for your reply,

That is a great suggestion! I've just tried to replicate the issue with Ozone and no, Segger's debugger does not crash in this situation.

Unfortunately I only have Nordic hardware at hand at the office so I won't be able to tell if this is an nRF only issue or not.

[Susheel Nuguru]

This seems like a debugger issue, it very much sounds like the gdb issues discussed in this forum

[lutrampal]

Indeed. Thank you for your time, I will mark this as resolved and see what the team Zephyr SDK team has to say.