linux-kernel - Re: [PATCH v2 1/9] kgdb: Disable WARN_CONSOLE

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Date:   Mon, 27 Apr 2020 14:40:39 +0100
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     jason.wessel@...driver.com, gregkh@...uxfoundation.org,
        kgdb-bugreport@...ts.sourceforge.net, mingo@...hat.com,
        hpa@...or.com, bp@...en8.de, linux-serial@...r.kernel.org,
        agross@...nel.org, tglx@...utronix.de, frowand.list@...il.com,
        bjorn.andersson@...aro.org, jslaby@...e.com,
        catalin.marinas@....com, corbet@....net, will@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/9] kgdb: Disable WARN_CONSOLE_UNLOCKED for all kgdb

On Tue, Apr 21, 2020 at 02:14:39PM -0700, Douglas Anderson wrote:
> In commit 81eaadcae81b ("kgdboc: disable the console lock when in
> kgdb") we avoided the WARN_CONSOLE_UNLOCKED() yell when we were in
> kgdboc.  That still works fine, but it turns out that we get a similar
> yell when using other I/O drivers.  One example is the "I/O driver"
> for the kgdb test suite (kgdbts).  When I enabled that I again got the
> same yells.
> 
> Even though "kgdbts" doesn't actually interact with the user over the
> console, using it still causes kgdb to print to the consoles.  That
> trips the same warning:
>   con_is_visible+0x60/0x68
>   con_scroll+0x110/0x1b8
>   lf+0x4c/0xc8
>   vt_console_print+0x1b8/0x348
>   vkdb_printf+0x320/0x89c
>   kdb_printf+0x68/0x90
>   kdb_main_loop+0x190/0x860
>   kdb_stub+0x2cc/0x3ec
>   kgdb_cpu_enter+0x268/0x744
>   kgdb_handle_exception+0x1a4/0x200
>   kgdb_compiled_brk_fn+0x34/0x44
>   brk_handler+0x7c/0xb8
>   do_debug_exception+0x1b4/0x228
> 
> Let's increment/decrement the "ignore_console_lock_warning" variable
> all the time when we enter the debugger.
> 
> This will allow us to later revert commit 81eaadcae81b ("kgdboc:
> disable the console lock when in kgdb").
> 
> Signed-off-by: Douglas Anderson <dianders@...omium.org>

Reviewed-by: Daniel Thompson <daniel.thompson@...aro.org>