Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20200914130143.1322802-1-daniel.thompson@linaro.org> <20200914130143.1322802-4-daniel.thompson@linaro.org>
In-Reply-To: <20200914130143.1322802-4-daniel.thompson@linaro.org>
From:   Doug Anderson <dianders@chromium.org>
Date:   Mon, 14 Sep 2020 17:13:28 -0700
Message-ID: <CAD=FV=VUPXdHoPaQg=Pp=bH-iORicO+1LjBZ0PNu0=SumC5tYw@mail.gmail.com>
Subject: Re: [PATCH v3 3/3] kernel: debug: Centralize dbg_[de]activate_sw_breakpoints
To:     Daniel Thompson <daniel.thompson@linaro.org>
Cc:     Jason Wessel <jason.wessel@windriver.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Sumit Garg <sumit.garg@linaro.org>,
        Petr Mladek <pmladek@suse.com>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Will Deacon <will@kernel.org>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        kgdb-bugreport@lists.sourceforge.net,
        LKML <linux-kernel@vger.kernel.org>,
        Patch Tracking <patches@linaro.org>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hi,

On Mon, Sep 14, 2020 at 6:02 AM Daniel Thompson
<daniel.thompson@linaro.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@linaro.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