Re: [PATCH] net/sunrpc: fix time conversion error

[Patrick McHardy <kaber@trash.net>]

Nishanth Aravamudan wrote:
> On 01.08.2005 [15:11:48 -0600], Josip Loncaric wrote:
> 
>>Line 589 of linux-2.6.11.10/net/sunrpc/svcsock.c is obviously wrong:
>>
>>                skb->stamp.tv_usec = xtime.tv_nsec * 1000;
>>
>>To convert nsec to usec, one should divide instead of multiplying:
>>
>>                skb->stamp.tv_usec = xtime.tv_nsec / 1000;
>>
>>The same bug could be present in the latest kernels, although I haven't 
>>checked.  This bug makes svc_udp_recvfrom() timestamps incorrect.
> 
> 
> Agreed, the conversion is wrong. I think the code is buggy period, as it
> accesses xtime without grabbing the xtime_lock first. Following patch
> should fix both issues.
> 
> Description: This function incorrectly multiplies a nanosecond value by
> 1000, instead of dividing by 1000, to obtain a corresponding microsecond
> value. Fix the math. Also, the function incorrectly accesses xtime
> without using the xtime_lock. Fixed as well. Patch is compile-tested.

Depending on in which release you want this patch included, you might
want to redo it against Dave's net-2.6.14 tree. It includes a patch that
changes skb->stamp to an offset against a base timestamp.

Regards
Patrick

PS: I'll submit the patch to break compilation for unconverted users
ASAP.