Re: [PATCH] powerpc/xmon: Fix data-breakpoint

From: Ravi Bangoria
Date: Tue Nov 22 2016 - 06:51:00 EST

Thanks Michael,

On Tuesday 22 November 2016 05:03 PM, Michael Ellerman wrote:
> Ravi Bangoria <ravi.bangoria@xxxxxxxxxxxxxxxxxx> writes:
>> Xmon data-breakpoint feature is broken.
>> Whenever there is a watchpoint match occurs, hw_breakpoint_handler will
>> be called by do_break via notifier chains mechanism. If watchpoint is
>> registered by xmon, hw_breakpoint_handler won't find any associated
>> perf_event and returns immediately with NOTIFY_STOP. Similarly, do_break
>> also returns without notifying to xmon.
>> Solve this by returning NOTIFY_DONE when hw_breakpoint_handler does not
>> find any perf_event associated with matched watchpoint.
> .. rather than NOTIFY_STOP, which tells the core code to continue
> calling the other breakpoint handlers including the xmon one.
> Right?


> Also any idea when we broke this?

Hmm, not sure exactly. The code is same since it was merged in 2010 when
support for hw_breakpoint was added for server processor.


> cheers