Bug 8479

Created attachment 11501 [details]
test program, used to get output.

Here's my output from running the program on the boxes I have available:

athena (core2duo, amd64)
    glibc-2.5-r2
    kernel 2.6.21-ck1
    done 10000000
    big 9 small 0

    glibc-2.5-r2
    kernel 2.6.21
    done 10000000
    big 13 small 0

    glibc-2.5-r2
    kernel 2.6.20
    done 10000000
    big 0 small 9

nemesis (athlon xp, x86)
    glibc-2.3.6-r4
    kernel 2.6.16-ck3
    done 10000000
    big 0 small 12

poseidon (sempron, amd64)
    glibc-2.5
    kernel 2.6.15-gentoo-r1
    done 10000000
    big 0 small 8

thanatos (athlon X2, amd64)
    glibc-2.5-r2
    kernel 2.6.20-ck1
    done 10000000
    big 0 small 13

    glibc-2.5-r2
    kernel 2.6.21
    done 10000000
    big 0 small 12

    glibc-2.5-r2
    kernel 2.6.21-ck1-r1
    done 10000000
    big 0 small 10

I consistently get overruns on my core2duo on 2.6.21 (and I *never* get 0
returned for tv_usec) and I always get valid values for all other combinations
of hardware and kernels.

Created attachment 11502 [details]
.config from failing 2.6.21 kernel

Reply-To: dada1@cosmosbay.com

Andrew Morton a 

> >
> > 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

-Andi

Reply-To: 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;
 	}

On Tue, 2007-05-15 at 10:17 +0200, Eric Dumazet wrote:
> 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;
>  	}

That fixed it, thanks.

Daniel

Reply-To: davidsen@tmr.com

Andrew Morton wrote:
> On Tue, 15 May 2007 08:06:52 +0200 Eric Dumazet <dada1@cosmosbay.com> wrote:
> 
>> Andrew Morton a 

Reply-To: dada1@cosmosbay.com

Bill Davidsen a 

Fixed in .21.stable:

http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6.21.y.git;a=commit;h=b07fee24dcefbeed5bdacb7e1b74e8423a2c20be