Re: [PATCH RFC nohz_full 0/8] Provide infrastructure for full-system idle

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

On Tue, Jun 25, 2013 at 11:49:47PM +0200, Thomas Gleixner wrote:
> On Tue, 25 Jun 2013, Paul E. McKenney wrote:
> > Note that this version pays attention to CPUs that have taken an NMI
> > from idle.  It is not clear to me that NMI handlers can safely access
> > the time on a system that is long-term idle.  Unless someone tells me
> > that it is somehow safe to access time from an NMI from idle, I will
> > remove NMI support in the next version.
> 
> NMI cannot access any time related functions independent of NOHZ, long
> term idle or whatever you come up with:
> 
>        write_seqcount_begin(&timekeeper_seq);
> 
> ---> NMI
> 	...
> 	do {
> 	   seq = read_seqcount_begin(&timekeeper_seq);
> 	} while (read_seqcount_retry(&timekeeper_seq, seq));
> 
> Guess how well that works ....

Woo-hoo!!!  I will yank the NMI support on the next version.  Thank
you for the info!

							Thanx, Paul