Re: [PATCH 3/3] log: Fetch log times with CLOCK_MONOTONIC, not CLOCK_REALTIME

[David Gibson <david@gibson.dropbear.id.au>]

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On Thu, Jul 25, 2024 at 06:26:34PM +0200, Stefano Brivio wrote:
> We report relative timestamps in logs, so we want to avoid jumps in
> the system time.
> 
> Suggested-by: David Gibson <david@gibson.dropbear.id.au>
> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

I noticed another pre-existing nit, though..

> ---
>  log.c   | 4 ++--
>  passt.c | 2 +-
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/log.c b/log.c
> index 9474bad..0fb25b7 100644
> --- a/log.c
> +++ b/log.c
> @@ -68,7 +68,7 @@ void vlogmsg(bool newline, int pri, const char *format, va_list ap)
>  	struct timespec tp;
>  
>  	if (debug_print) {
> -		clock_gettime(CLOCK_REALTIME, &tp);
> +		clock_gettime(CLOCK_MONOTONIC, &tp);
>  		fprintf(stderr, logtime_fmt_and_arg(&tp));
>  		fprintf(stderr, ": ");
>  	}
> @@ -382,7 +382,7 @@ void logfile_write(bool newline, int pri, const char *format, va_list ap)
>  	char buf[BUFSIZ];
>  	int n;
>  
> -	if (clock_gettime(CLOCK_REALTIME, &now))
> +	if (clock_gettime(CLOCK_MONOTONIC, &now))

We have two separate calls to get the time for "this" message.  I
think this means under the right circumstances we could have
essentially the same message logged to different places with
(slightly) different times.  That seems needlessly confusing.  It
would be nice to have a single point at which we capture the time for
a single message.

>  		return;
>  
>  	n  = snprintf(buf, BUFSIZ, logtime_fmt_and_arg(&now));
> diff --git a/passt.c b/passt.c
> index 72ad704..6401730 100644
> --- a/passt.c
> +++ b/passt.c
> @@ -207,7 +207,7 @@ int main(int argc, char **argv)
>  	struct timespec now;
>  	struct sigaction sa;
>  
> -	clock_gettime(CLOCK_REALTIME, &log_start);
> +	clock_gettime(CLOCK_MONOTONIC, &log_start);
>  
>  	arch_avx2_exec(argv);
>  

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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