From: Ahmad Fatoum <a.fatoum@pengutronix.de>
To: barebox@lists.infradead.org
Cc: Ahmad Fatoum <a.fatoum@pengutronix.de>
Subject: [PATCH] commands: uptime: add note about caveats
Date: Wed, 2 Nov 2022 09:50:17 +0100 [thread overview]
Message-ID: <20221102085017.1941580-1-a.fatoum@pengutronix.de> (raw)
Normally timer overrun is not that much of a problem, because there
where it matters, we usually have an is_timeout() in the loop that reads
the timer often enough. This doesn't necessarily hold for the new uptime
command and basically anything can happen between subsequent calls and
if get_time_ns() is not called often enough during that time, we end up
with an inaccurate uptime. Mention this in the extended help text.
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
Can be squashed into original commit.
---
commands/uptime.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/commands/uptime.c b/commands/uptime.c
index a9a8c650b698..d67538631c8f 100644
--- a/commands/uptime.c
+++ b/commands/uptime.c
@@ -66,6 +66,9 @@ static int do_uptime(int argc, char *argv[])
BAREBOX_CMD_HELP_START(uptime)
BAREBOX_CMD_HELP_TEXT("This command formats the number of elapsed nanoseconds")
BAREBOX_CMD_HELP_TEXT("as measured with the current clocksource")
+BAREBOX_CMD_HELP_TEXT("Note: Timekeeping is co-operative. If long running code does")
+BAREBOX_CMD_HELP_TEXT("not use delay/is_timeout/get_time_ns/getchar functions")
+BAREBOX_CMD_HELP_TEXT("timer may overrun resulting in incorrect results")
BAREBOX_CMD_HELP_TEXT("Options:")
BAREBOX_CMD_HELP_OPT ("-n", "output elapsed time in nanoseconds")
BAREBOX_CMD_HELP_END
--
2.30.2
next reply other threads:[~2022-11-02 8:51 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-02 8:50 Ahmad Fatoum [this message]
2022-11-04 8:54 ` Sascha Hauer
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