Why the mce reverts in 4.16-rt?

Why the mce reverts in 4.16-rt?

[Steven Rostedt]

Hi Sebastian,

I'm looking at backporting patches from 4.16-rt and noticed that you
have:

Revert "x86: Convert mce timer to hrtimer"
Revert "x86/mce: use swait queue for mce wakeups"

With no explanation to why they were reverted. When did things change?
Should this be 4.14-rt material?

Thanks,

-- Steve

Re: Why the mce reverts in 4.16-rt?

[Sebastian Andrzej Siewior]

On 2018-07-10 20:56:24 [-0400], Steven Rostedt wrote:
> Hi Sebastian,
Hi Steven,

> I'm looking at backporting patches from 4.16-rt and noticed that you
> have:
> 
> Revert "x86: Convert mce timer to hrtimer"
> Revert "x86/mce: use swait queue for mce wakeups"
> 
> With no explanation to why they were reverted. When did things change?
> Should this be 4.14-rt material?

from the announce email:
|    Changes since v4.16.8-rt2:
|    
|      - Drop two MCE related patches. They are no longer required since the
|        timer wheel rework.

The timer wheel rework made it possible to have a raw_spin_lock_t in the
timer_list timer. The problem with MCE was that it enqueued a timer from
hardirq context which is now possible. So the patches are no longer
required. This revert does not fix a bug in v4.14 nor does it break
anything.

> Thanks,
> 
> -- Steve

Sebastian

Re: Why the mce reverts in 4.16-rt?

[Steven Rostedt]

On Wed, 11 Jul 2018 09:23:11 +0200
Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote:

> On 2018-07-10 20:56:24 [-0400], Steven Rostedt wrote:
> > Hi Sebastian,  
> Hi Steven,
> 
> > I'm looking at backporting patches from 4.16-rt and noticed that you
> > have:
> > 
> > Revert "x86: Convert mce timer to hrtimer"
> > Revert "x86/mce: use swait queue for mce wakeups"
> > 
> > With no explanation to why they were reverted. When did things change?
> > Should this be 4.14-rt material?  
> 
> from the announce email:
> |    Changes since v4.16.8-rt2:
> |    
> |      - Drop two MCE related patches. They are no longer required since the
> |        timer wheel rework.

Thanks, still would have preferred a comment in the revert commit
message ;-)

> 
> The timer wheel rework made it possible to have a raw_spin_lock_t in the
> timer_list timer. The problem with MCE was that it enqueued a timer from
> hardirq context which is now possible. So the patches are no longer
> required. This revert does not fix a bug in v4.14 nor does it break
> anything.

OK, even though this doesn't fix anything, I think I'll still
backport it.

-- Steve