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

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Date:   Tue, 22 Nov 2016 22:33:51 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
Cc:     benh@...nel.crashing.org, paulus@...ba.org, npiggin@...il.com,
        peterz@...radead.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, naveen.n.rao@...ux.vnet.ibm.com,
        Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
Subject: Re: [PATCH] powerpc/xmon: Fix data-breakpoint

Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com> 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?

cheers