From: Petr Mladek <pmladek@suse.com>
To: Sumit Garg <sumit.garg@linaro.org>
Cc: daniel.thompson@linaro.org, kgdb-bugreport@lists.sourceforge.net,
jason.wessel@windriver.com, dianders@chromium.org,
sergey.senozhatsky@gmail.com, gregkh@linuxfoundation.org,
jslaby@suse.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v6 4/4] kdb: Switch to use safer dbg_io_ops over console APIs
Date: Fri, 5 Jun 2020 11:53:56 +0200 [thread overview]
Message-ID: <20200605095356.GK22497@linux-b0ei> (raw)
In-Reply-To: <1591264879-25920-5-git-send-email-sumit.garg@linaro.org>
On Thu 2020-06-04 15:31:19, Sumit Garg wrote:
> In kgdb context, calling console handlers aren't safe due to locks used
> in those handlers which could in turn lead to a deadlock. Although, using
> oops_in_progress increases the chance to bypass locks in most console
> handlers but it might not be sufficient enough in case a console uses
> more locks (VT/TTY is good example).
>
> Currently when a driver provides both polling I/O and a console then kdb
> will output using the console. We can increase robustness by using the
> currently active polling I/O driver (which should be lockless) instead
> of the corresponding console. For several common cases (e.g. an
> embedded system with a single serial port that is used both for console
> output and debugger I/O) this will result in no console handler being
> used.
>
> In order to achieve this we need to reverse the order of preference to
> use dbg_io_ops (uses polling I/O mode) over console APIs. So we just
> store "struct console" that represents debugger I/O in dbg_io_ops and
> while emitting kdb messages, skip console that matches dbg_io_ops
> console in order to avoid duplicate messages. After this change,
> "is_console" param becomes redundant and hence removed.
>
> Suggested-by: Daniel Thompson <daniel.thompson@linaro.org>
> Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
Looks good to me now:
Reviewed-by: Petr Mladek <pmladek@suse.com>
Best Regards,
Petr
next prev parent reply other threads:[~2020-06-05 9:54 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-04 10:01 [PATCH v6 0/4] kdb: Improve console handling Sumit Garg
2020-06-04 10:01 ` [PATCH v6 1/4] kdb: Re-factor kdb_printf() message write code Sumit Garg
2020-06-04 10:01 ` [PATCH v6 2/4] kdb: Check status of console prior to invoking handlers Sumit Garg
2020-06-04 10:01 ` [PATCH v6 3/4] kdb: Make kdb_printf() console handling more robust Sumit Garg
2020-06-04 10:01 ` [PATCH v6 4/4] kdb: Switch to use safer dbg_io_ops over console APIs Sumit Garg
2020-06-04 21:12 ` Doug Anderson
2020-06-05 9:53 ` Petr Mladek [this message]
2020-06-26 12:13 ` Daniel Thompson
2020-06-26 14:19 ` Greg KH
2020-06-05 3:57 ` [PATCH v6 0/4] kdb: Improve console handling Sergey Senozhatsky
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