[rhelv6-list] A kernel bug that causes a system crash when the uptime is longer than 208.5 days

[Akemi Yagi]

On Fri, Jan 6, 2012 at 8:55 AM, Akemi Yagi <amyagi at gmail.com> wrote:
> On Fri, Jan 6, 2012 at 8:55 AM, Robin Price II <rprice at redhat.com> wrote:
>> Bugzilla:  https://bugzilla.redhat.com/show_bug.cgi?id=765720
>>
>> This is private due to private information from customer use cases.  If you
>> need further details, I would highly encourage you to contact Red Hat
>> support or your TAM.
>>
>> Here is the initial information opened in the BZ:
>>
>> "The following patch is in urgent fix for Linus branch, which avoid the
>> unnecessary overflow in sched_clock otherwise kernel will crash after
>> 209~250 days.
>>
>> http://git.kernel.org/?p=linux/kernel/git/tip/tip.git;a=patch;h=4cecf6d401a01d054afc1e5f605bcbfe553cb9b9
>>
>> In hundreds of days, the __cycles_2_ns calculation in sched_clock
>> has an overflow.  cyc * per_cpu(cyc2ns, cpu) exceeds 64 bits, causing the
>> final value to become zero.  We can solve this without losing any precision.
>> We can decompose TSC into quotient and remainder of division by the scale
>> factor, and then use this to convert TSC into nanoseconds."
>>
>> ~rp
>
> Thank you for this post to let us know that Red Hat is now taking care
> of this issue.

Just a note to add that there is a KB article for this issue:

https://access.redhat.com/kb/docs/DOC-69254
"sched_clock() overflow after 208.5 days in Linux Kernel"

Akemi