[Bug 1921092] [NEW] qemu-system-arm multi core debug not working

[Bug 1921092] [NEW] qemu-system-arm multi core debug not working

[Martin Schönstedt]

Public bug reported:

Working with Zephyr RTOS, running a multi core sample on mps2_an521 works fine. Both cpus start.
Trying to debug with options -s -S the second core fails to boot.
Posted with explanation also at: https://github.com/zephyrproject-rtos/zephyr/issues/33635

** Affects: qemu
     Importance: Undecided
         Status: New


** Tags: arm debug

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Title:
  qemu-system-arm multi core debug not working

Status in QEMU:
  New

Bug description:
  Working with Zephyr RTOS, running a multi core sample on mps2_an521 works fine. Both cpus start.
  Trying to debug with options -s -S the second core fails to boot.
  Posted with explanation also at: https://github.com/zephyrproject-rtos/zephyr/issues/33635

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[Bug 1921092] Re: qemu-system-arm multi core debug not working

[Martin Schönstedt]

** Description changed:

  Working with Zephyr RTOS, running a multi core sample on mps2_an521 works fine. Both cpus start.
  Trying to debug with options -s -S the second core fails to boot.
  Posted with explanation also at: https://github.com/zephyrproject-rtos/zephyr/issues/33635
+ 
+ only after closing the gdb server the second core boots and execution continues normally.
+ Is there no way to debug such a multi core environment?

** Description changed:

  Working with Zephyr RTOS, running a multi core sample on mps2_an521 works fine. Both cpus start.
  Trying to debug with options -s -S the second core fails to boot.
  Posted with explanation also at: https://github.com/zephyrproject-rtos/zephyr/issues/33635
  
- only after closing the gdb server the second core boots and execution continues normally.
+ only after quitting the debugging session the second core boots and execution continues normally.
  Is there no way to debug such a multi core environment?

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Title:
  qemu-system-arm multi core debug not working

Status in QEMU:
  New

Bug description:
  Working with Zephyr RTOS, running a multi core sample on mps2_an521 works fine. Both cpus start.
  Trying to debug with options -s -S the second core fails to boot.
  Posted with explanation also at: https://github.com/zephyrproject-rtos/zephyr/issues/33635

  only after quitting the debugging session the second core boots and execution continues normally.
  Is there no way to debug such a multi core environment?

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[Bug 1921092] Re: qemu-system-arm multi core debug not working

[Martin Schönstedt]

there was no bug, it was my fault. How do I delete this

** Changed in: qemu
       Status: New => Invalid

** Summary changed:

- qemu-system-arm multi core debug not working
+ how do i delete this bug?

** Description changed:

- Working with Zephyr RTOS, running a multi core sample on mps2_an521 works fine. Both cpus start.
- Trying to debug with options -s -S the second core fails to boot.
- Posted with explanation also at: https://github.com/zephyrproject-rtos/zephyr/issues/33635
- 
- only after quitting the debugging session the second core boots and execution continues normally.
- Is there no way to debug such a multi core environment?
+ no bugs here

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Title:
  how do i delete this bug?

Status in QEMU:
  Invalid

Bug description:
  no bugs here

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[Bug 1921092] Re: how do i delete this bug?

[Peter Maydell]

In general, you don't need to delete bugs that turn out to be user
error, or edit the description/title; just mark them as 'invalid',
perhaps with a comment about what turned out to be the cause. That
leaves the trail of what was going on for future readers who might be
going down the same path as you.

There are actually a couple of things we should do here in upstream
QEMU:

* we should document the process for using the debugstub with multi-cluster board models like the mps2-an521
* we should check whether we are doing the right/most appropriate thing when the user connects to the debug stub and is only attaching to one 'inferior' -- it sounds from your report like the un-attached inferior is left permanently in the 'stopped' state. Maybe that's what the gdb protocol requires, but it seems a bit unhelpful.

I'm going to update the bug status/text accordingly.


** Summary changed:

- how do i delete this bug?
+ gdbstub debug of multi-cluster machines is undocumented and confusing

** Changed in: qemu
       Status: Invalid => Confirmed

** Description changed:

- no bugs here
+ Working with Zephyr RTOS, running a multi core sample on mps2_an521 works fine. Both cpus start.
+ Trying to debug with options -s -S the second core fails to boot.
+ 
+ Posted with explanation also at: https://github.com/zephyrproject-
+ rtos/zephyr/issues/33635

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Title:
  gdbstub debug of multi-cluster machines is undocumented and confusing

Status in QEMU:
  Confirmed

Bug description:
  Working with Zephyr RTOS, running a multi core sample on mps2_an521 works fine. Both cpus start.
  Trying to debug with options -s -S the second core fails to boot.

  Posted with explanation also at: https://github.com/zephyrproject-
  rtos/zephyr/issues/33635

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[Bug 1921092] Re: gdbstub debug of multi-cluster machines is undocumented and confusing

[Martin Schönstedt]

Thanks for the answer,

indeed the second cluster of the board has been halted when I was
starting gdb the "normal" way - not adding the second inferior. In my
own research I did not find out about these inferiors, so I was
wondering why "info threads" did only show one cpu. Maybe gdb could
inform the user about unattached inferiors when using "info threads"

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Title:
  gdbstub debug of multi-cluster machines is undocumented and confusing

Status in QEMU:
  Confirmed

Bug description:
  Working with Zephyr RTOS, running a multi core sample on mps2_an521 works fine. Both cpus start.
  Trying to debug with options -s -S the second core fails to boot.

  Posted with explanation also at: https://github.com/zephyrproject-
  rtos/zephyr/issues/33635

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[Bug 1921092] Re: gdbstub debug of multi-cluster machines is undocumented and confusing

[Peter Maydell]

Could you provide an example QEMU command line and guest image file
which you were having this problem with, please? That would save me
figuring out how to build zephyr binaries :-)

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Title:
  gdbstub debug of multi-cluster machines is undocumented and confusing

Status in QEMU:
  Confirmed

Bug description:
  Working with Zephyr RTOS, running a multi core sample on mps2_an521 works fine. Both cpus start.
  Trying to debug with options -s -S the second core fails to boot.

  Posted with explanation also at: https://github.com/zephyrproject-
  rtos/zephyr/issues/33635

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[Bug 1921092] Re: gdbstub debug of multi-cluster machines is undocumented and confusing

[Martin Schönstedt]

qemu-system-arm -cpu cortex-m33 -machine mps2-an521 -nographic -m 16
-vga none -net none -chardev stdio,id=con,mux=on -serial chardev:con
-mon chardev=con,mode=readline -icount shift=7,align=off,sleep=off -rtc
clock=vm -device loader,file=<remote_dir>/zephyr.elf -s -S -kernel
<master_dir>/zephyr.elf

i've included both .elf files in a zip. That should be enough for
running the sample

** Attachment added: "zephyr_sample.zip"
   https://bugs.launchpad.net/qemu/+bug/1921092/+attachment/5480969/+files/zephyr_sample.zip

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Title:
  gdbstub debug of multi-cluster machines is undocumented and confusing

Status in QEMU:
  Confirmed

Bug description:
  Working with Zephyr RTOS, running a multi core sample on mps2_an521 works fine. Both cpus start.
  Trying to debug with options -s -S the second core fails to boot.

  Posted with explanation also at: https://github.com/zephyrproject-
  rtos/zephyr/issues/33635

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[Bug 1921092] Re: gdbstub debug of multi-cluster machines is undocumented and confusing

[Peter Maydell]

There's now a new docs section on debugging multicore (including multi-
cluster) machines:

https://qemu-project.gitlab.io/qemu/system/gdb.html#debugging-multicore-
machines

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Title:
  gdbstub debug of multi-cluster machines is undocumented and confusing

Status in QEMU:
  Confirmed

Bug description:
  Working with Zephyr RTOS, running a multi core sample on mps2_an521 works fine. Both cpus start.
  Trying to debug with options -s -S the second core fails to boot.

  Posted with explanation also at: https://github.com/zephyrproject-
  rtos/zephyr/issues/33635

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[Bug 1921092] Re: gdbstub debug of multi-cluster machines is undocumented and confusing

[Thomas Huth]

Is there still anything to do here or could we close the ticket now?

** Changed in: qemu
       Status: Confirmed => Incomplete

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Title:
  gdbstub debug of multi-cluster machines is undocumented and confusing

Status in QEMU:
  Incomplete

Bug description:
  Working with Zephyr RTOS, running a multi core sample on mps2_an521 works fine. Both cpus start.
  Trying to debug with options -s -S the second core fails to boot.

  Posted with explanation also at: https://github.com/zephyrproject-
  rtos/zephyr/issues/33635

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[Bug 1921092] Re: gdbstub debug of multi-cluster machines is undocumented and confusing

[Martin Schönstedt]

It can be closed. The added documentation is very helpful.

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Title:
  gdbstub debug of multi-cluster machines is undocumented and confusing

Status in QEMU:
  Incomplete

Bug description:
  Working with Zephyr RTOS, running a multi core sample on mps2_an521 works fine. Both cpus start.
  Trying to debug with options -s -S the second core fails to boot.

  Posted with explanation also at: https://github.com/zephyrproject-
  rtos/zephyr/issues/33635

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[Bug 1921092] Re: gdbstub debug of multi-cluster machines is undocumented and confusing

[Thomas Huth]

Ok, thanks, so I'm closing this ticket now.

** Changed in: qemu
       Status: Incomplete => Fix Released

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Title:
  gdbstub debug of multi-cluster machines is undocumented and confusing

Status in QEMU:
  Fix Released

Bug description:
  Working with Zephyr RTOS, running a multi core sample on mps2_an521 works fine. Both cpus start.
  Trying to debug with options -s -S the second core fails to boot.

  Posted with explanation also at: https://github.com/zephyrproject-
  rtos/zephyr/issues/33635

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