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dave2012
dave2012
Associate III
February 17, 2020
Question

CPU freezing when inserting or removing a breakpoint

  • February 17, 2020
  • 2 replies
  • 602 views

Hi,

I've come across an issue whereby inserting or removing a breakpoint anywhere in my code when the processor is running causes execution to pause for ~180ms. I thought manipulation of breakpoint registers was independent of processsor execution state.

Is this delay to be expected ?

I'm using a STM32F7, ST-Linkv3 and OpenOCD with STM32CubeIDE v1.2.

Thanks

Dave

This topic has been closed for replies.

2 replies

mattias norlander
mattias norlander
ST Employee
February 21, 2020

Yes it is expected. gdb halts the core to set or unset a breakpoint and then resumes the program execution,: All-in-all this takes about ~180ms.

Ozone
Ozone
Principal
February 21, 2020

Other toolchains can do it without visibly affecting the target.

OTOH, I'm also working with toolchains which are unable to set breakpoints when running.

dave2012
dave2012Author
Associate III
February 21, 2020

Thanks for confirming Mattias, at least I'm not going mad. It's a real problem as it causes comms link timeouts.

I've tried setting a breakpoint in OpenOCD via Telnet and this works fine without halting the CPU. However, when I try to remove the breakpoint it complains that the target is not halted and the breakpoint remains set.

I've tried selecting JLink as the debug adapter (different GDB server) and this also results in halting the CPU when setting a breakpoint. Maybe you'd expect this too?

It would be really helpful to get a workaround for this if possible. As @Ozone​ says, there are tools that don't halt the CPU (I never came across this issue with Keil uVision for example).

Dave

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