linux-kernel - Re: [PATCH v3 3/3] kernel: debug: Centralize dbg_[de]activate_sw

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Date:   Mon, 14 Sep 2020 17:13:28 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Daniel Thompson <daniel.thompson@...aro.org>
Cc:     Jason Wessel <jason.wessel@...driver.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Sumit Garg <sumit.garg@...aro.org>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Will Deacon <will@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        kgdb-bugreport@...ts.sourceforge.net,
        LKML <linux-kernel@...r.kernel.org>,
        Patch Tracking <patches@...aro.org>
Subject: Re: [PATCH v3 3/3] kernel: debug: Centralize dbg_[de]activate_sw_breakpoints

Hi,

On Mon, Sep 14, 2020 at 6:02 AM Daniel Thompson
<daniel.thompson@...aro.org> wrote:
>
> During debug trap execution we expect dbg_deactivate_sw_breakpoints()
> to be paired with an dbg_activate_sw_breakpoint(). Currently although
> the calls are paired correctly they are needlessly smeared across three
> different functions. Worse this also results in code to drive polled I/O
> being called with breakpoints activated which, in turn, needlessly
> increases the set of functions that will recursively trap if breakpointed.
>
> Fix this by moving the activation of breakpoints into the debug core.
>
> Signed-off-by: Daniel Thompson <daniel.thompson@...aro.org>
> ---
>  kernel/debug/debug_core.c       | 2 ++
>  kernel/debug/gdbstub.c          | 1 -
>  kernel/debug/kdb/kdb_debugger.c | 2 --
>  3 files changed, 2 insertions(+), 3 deletions(-)

I like the idea, but previously the kgdb_arch_handle_exception() was
always called after the SW breakpoints were activated.  Are you sure
it's OK to swap those two orders across all architectures?

-Doug