Re: [Bugme-new] [Bug 8479] New: gettimeofday returning 1000000 in tv_usec on core2duo

[Eric Dumazet <dada1@cosmosbay.com>]

On Tue, 15 May 2007 09:22:47 +0200
Andi Kleen <ak@suse.de> wrote:

> 
> > >
> > > I remember I already hit this and corrected it
> > >
> > > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blobdi
> > >ff;f=arch/x86_64/kernel/vsyscall.c;h=dc32cef961950915fbaa185e36ab802d5f7ce
> > >a3b;hp=ba330f87067996a17495f7d03466d646c718b52c;hb=c8118c6c07f2edfd697aaa0
> > >b93e08c3b65a5a675;hpb=272a3713bb9e302e0455c894c41180a482d2c8a3
> >
> > Oh, OK.
> >
> > > Maybe a stable push is necessary ?
> >
> > yup.  Please always think of -stable when preparing fixes.  I'm sure many
> > useful fixes are slipping past simply because those who _are_ looking out
> > for backportable fixes are missing things.
> >
> > Greg, Chris: please consider c8118c6c07f2edfd697aaa0b93e08c3b65a5a675
> > for -stable, if it isn't already there.
> 
> The full patch is overkill because 99% of it is an totally unrelated 
> optimization. Only the > -> >= change should be backported

OK, here is the fix only patch, for linux-2.6.21-stable only, since 2.6.22 is already fixed.

[PATCH] x86_64 : Fix vgettimeofday()

vgettimeofday() may return some bad timeval values, (tv_usec = 1000000), because of a wrong compare.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>

--- arch/x86_64/kernel/vsyscall.c
+++ arch/x86_64/kernel/vsyscall.c
@@ -132,7 +132,7 @@ static __always_inline void do_vgettimeo
 
 	/* convert to usecs and add to timespec: */
 	tv->tv_usec += nsec_delta / NSEC_PER_USEC;
-	while (tv->tv_usec > USEC_PER_SEC) {
+	while (tv->tv_usec >= USEC_PER_SEC) {
 		tv->tv_sec += 1;
 		tv->tv_usec -= USEC_PER_SEC;
 	}
-
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