linux-kernel - Re: [PATCH] kdb: Change timespec to use timespec64

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Message-ID: <CAK8P3a2BtM-oW4ZVRg6S6aS30b4FD9MHvQWP4hKuGC1XXbbG1g@mail.gmail.com>
Date:   Thu, 25 Jan 2018 09:55:51 +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] kdb: Change timespec to use timespec64

On Thu, Jan 25, 2018 at 9:05 AM, Baolin Wang <baolin.wang@...aro.org> wrote:
> @@ -2554,7 +2554,7 @@ static int kdb_summary(int argc, const char **argv)
>         kdb_printf("domainname %s\n", init_uts_ns.name.domainname);
>         kdb_printf("ccversion  %s\n", __stringify(CCVERSION));
>
> -       now = __current_kernel_time();
> +       now = current_kernel_time64();
>         kdb_gmtime(&now, &tm);
>         kdb_printf("date       %04d-%02d-%02d %02d:%02d:%02d "
>                    "tz_minuteswest %d\n",

Thanks for picking this one up again, we should find a permanent solution here.
Unfortunately you patch is incorrect, as we cannot safely call
current_kernel_time64()
from NMI context.

The __ prefix on __current_kernel_time() indicates that this is a special call
that intentionally doesn't read the hardware time to avoid taking locks that
might already be held in the context from which we entered the debugger.

See https://patchwork.kernel.org/patch/10002097/ for my earlier patch.

> @@ -2521,8 +2521,8 @@ static void kdb_gmtime(struct timespec *tv, struct kdb_tm *tm)
>   */
>  static void kdb_sysinfo(struct sysinfo *val)
>  {
> -       struct timespec uptime;
> -       ktime_get_ts(&uptime);
> +       struct timespec64 uptime;
> +       ktime_get_ts64(&uptime);
>         memset(val, 0, sizeof(*val));
>         val->uptime = uptime.tv_sec;
>         val->loads[0] = avenrun[0];

This function appears to have the same problem, except that it is a preexisting
issue in this case. I had not noticed this earlier, but we must fix it
in a similar
manner to the other one.

        Arnd