On 04/19/2016 04:56 AM, Petr Mladek wrote:
> On Mon 2016-04-18 11:30:52, Prarit Bhargava wrote:
> Hmm, If you allow to change the timestamp format only at boot time, it
> will make things easier. I just wonder if it would work correctly for
> early messages. For example, are there any messages printed before
> the real time clock is initialized? Which timestamp will they use?
>
> Also note that you still need to modify the dmesg code. It must
> not add boot_time when real time timestamp is used.
>
I've got a util-linux patch in-hand that does this (sorry for the
cut-and-paste) and I've verified that ctime, delta, iso, notime and
reltime all appear to work 1) without my kernel patches applied,
2) with my kernel patches applied, and 3) with printk.time=[0-3]
as kernel parameters.
diff --git a/sys-utils/dmesg.c b/sys-utils/dmesg.c
index cf93331..c49a202 100644
--- a/sys-utils/dmesg.c
+++ b/sys-utils/dmesg.c
@@ -1194,9 +1194,31 @@ static int which_time_format(const char *optarg)
errx(EXIT_FAILURE, _("unknown time format: %s"), optarg);
}
-#ifdef TEST_DMESG
+static int needs_boot_time(void)
+{
+ FILE *fd;
+ int ret = 1;
+ int val;
+
+ /*
+ * Newer kernels have /sys/modules/printk/parameter/time = [0-3]
+ * where 0 = off, 1 = local clock, 2 = boot time, and 3 = real time.
+ * If the file isn't present it means the functionality isn't there
+ * and the boot_time offset is needed.
+ */
+ fd = fopen("/sys/module/printk/parameters/time", "r");
+ if (!fd)
+ return ret;
+ fscanf(fd, "%d", &val);
+ if (val == 3)
+ ret = 0;
+ fclose(fd);
+ return ret;
+}
+
static inline int dmesg_get_boot_time(struct timeval *tv)
{
+#ifdef TEST_DMESG
char *str = getenv("DMESG_TEST_BOOTIME");
uintmax_t sec, usec;
@@ -1205,12 +1227,15 @@ static inline int dmesg_get_boot_time(struct timeval
*tv)
tv->tv_usec = usec;
return tv->tv_sec >= 0 && tv->tv_usec >= 0 ? 0 : -EINVAL;
}
+#endif
+
+ if (needs_boot_time())
+ return get_boot_time(tv);
- return get_boot_time(tv);
+ tv->tv_sec = 0;
+ tv->tv_usec = 0;
+ return 0;
}
-#else
-# define dmesg_get_boot_time get_boot_time
-#endif
int main(int argc, char *argv[])
{
--
1.8.3.1
> And you need to modify also the other tools, e.g. crash.
>
I spoke with [email protected] this morning and he agrees
that no change should be necessary for crash. A quick test shows that
the logging mechanism (dmesg or log) works after the patches are applied
and printk is in REALTIME mode.
IMO dmesg is the big one and I will modify that after I see acceptance
of this patch.
P.
