Messages in this thread | | | From | "Ulrich Windl" <> | Date | Fri, 08 Nov 2002 10:57:08 +0100 | Subject | Re: [TRIVIAL] 2.4.19 Fix adjtimex when txc->modes == 0 |
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Rusty,
your EMail address (Rusty Trivial Russell <@rustcorp.com.au>) is broken. I'm replying to linux-kernel instead.
I had reported this problem a long time (over a year at least) to the list. I found no 100% solution that is compatible with the old kernel version.
Best solution would be to separate the NTP functionality (ntp_adjtime, ntp_gettime) from adjtime() in the kernel.
I wonder how adjtime(NULL, non_null) is implemented: If "modes == 0" adjtimex() will emulate ntp_gettime() if "modes & ADJ_OFFSET_SINGLESHOT" is set with "txc->offset == 0", the current correction will be stopped. You must distinguish it from a call to adjtime(non_null, non_null) with an offset of 0 that will terminate the current correction.
(Manual says: "The second call to adjtime() stops the first call to adjtime() if delta is non-NULL, but does not undo the effects of the previous call. If delta is NULL, then no time correction will be done.")
If adjtimex() still should implement both library styles (ntp_*, and adjtime()), the clean solution would be a new flag like ADJ_OFFSET_QUERY (or ADJ_OFFSET_NO_SHOT or ADJ_OFFSET_PEACE). [Well I'm beginning to like the last one ;- )]
If adjtime(NULL, any) is used in Clib, adjtimex would have to be called with the ADJ_OFFSET_PEACE flag, avoiding to disturb the adjustment. If `any' is non-NULL, the offset would be returned to user land.
Rehards, Ulrich
On 8 Nov 2002 at 18:51, Rusty Trivial Russell wrote:
> Ulrich, does this look good to you? > > From: "Michael Kerrisk" <m.kerrisk@gmx.net> > > Hello Marcelo (or Rusty does this belong you as TPM?), > > I did try submitting it against 2.4.18pre10 but this patch > didn't seem to make it. The problem still exists in 2.4.19. > > The glibc implementation of adjtime(delta, old_delta) should return > the remaining time adjustment value from adjtimex() in old_delta if that > argument is non-NULL. > > This is broken in the case that delta is NULL (i.e., we don't want > a change, but just to find out the current time_adjust). The breakage > occurs because adjtime specifies txc->modes as 0 (so that no change > is made to the current offset) and in this case do_adjtimex() does not > correctly return the required information in txc->offset. > > The patch below (against 2.4.19) seems to me the best way to > fix the problem. > > Cheers, > > Michael > > > --- trivial-2.5-bk/kernel/time.c.orig 2002-11-08 18:46:34.000000000 +1100 > +++ trivial-2.5-bk/kernel/time.c 2002-11-08 18:46:34.000000000 +1100 > @@ -361,7 +361,9 @@ > /* p. 24, (d) */ > result = TIME_ERROR; > > - if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT) > + if (!txc->modes) > + txc->offset = time_adjust; > + else if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT) > txc->offset = save_adjust; > else { > if (time_offset < 0) > -- > Don't blame me: the Monkey is driving > File: "Michael Kerrisk" <m.kerrisk@gmx.net>: [patch] 2.4.19 Fix adjtimex when txc->modes == 0
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