linux-kernel - Re: [PATCH v2] kdb: use ktime_get_mono_fast_ns() instead of ktime_get

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Message-ID: <CAK8P3a1_tNGhqN+tbfbxtpdPJ+=ksNS4QJ=sPYCz7ORAqKVQAw@mail.gmail.com>
Date:   Tue, 30 Jan 2018 14:35:23 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Baolin Wang <baolin.wang@...aro.org>
Cc:     Jason Wessel <jason.wessel@...driver.com>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Ingo Molnar <mingo@...nel.org>,
        Mark Brown <broonie@...nel.org>,
        kgdb-bugreport@...ts.sourceforge.net,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] kdb: use ktime_get_mono_fast_ns() instead of ktime_get_ts()

On Mon, Jan 29, 2018 at 3:22 AM, Baolin Wang <baolin.wang@...aro.org> wrote:
> The kdb code will print the monotonic time by ktime_get_ts(), but
> the ktime_get_ts() will be protected by a sequence lock, that will
> introduce one deadlock risk if the lock was already held in the
> context from which we entered the debugger.
>
> Thus we can use the ktime_get_mono_fast_ns() to get the monotonic
> time, which is NMI safe access to clock monotonic. Moreover we can
> remove the 'struct timespec', which is not y2038 safe.
>
> Signed-off-by: Baolin Wang <baolin.wang@...aro.org>

Reviewed-by: Arnd Bergmann <arnd@...db.de>