Re: [PATCH] time: Add locking to xtime access in get_seconds()

Andi Kleen
2011-05-04T21:05:47Z

Max Asbock <masbock@linux.vnet.ibm.com> writes:

> On Tue, 2011-05-03 at 20:11 -0700, John Stultz wrote:
>> From: John Stultz <johnstul@us.ibm.com>
>>
>> So get_seconds() has always been lock free, with the assumption
>> that accessing a long will be atomic.
>>
>
> get_seconds() is used in the x86 machine check handler and there is a
> comment saying:
> /* We hope get_seconds stays lockless */
>
> This needs to be carefully looked at if locking is introduced to
> get_seconds().

Yes the seqlock being interrupted by an MCE would deadlock.

-Andi
--
ak@linux.intel.com -- Speaking for myself only