On Mon, Mar 22, 2021 at 02:40:32PM +0100, Uwe Kleine-König wrote:

Hello Johan,

On Mon, Mar 22, 2021 at 02:20:57PM +0100, Johan Hovold wrote:

quoted

On Mon, Mar 22, 2021 at 12:55:36PM +0100, Uwe Kleine-König wrote:

quoted

On Mon, Mar 22, 2021 at 12:39:18PM +0100, Sebastian Andrzej Siewior wrote:

quoted

On 2021-03-22 12:34:02 [+0100], Uwe Kleine-König wrote:

quoted

On Mon, Mar 22, 2021 at 12:10:36PM +0100, Johan Hovold wrote:

quoted

Force-threaded interrupt handlers used to run with interrupts enabled,
something which could lead to deadlocks in case a threaded handler
shared a lock with code running in hard interrupt context (e.g. timer
callbacks) and did not explicitly disable interrupts.

This was specifically the case for serial drivers that take the port
lock in their console write path as printk can be called from hard
interrupt context also with forced threading ("threadirqs").

Since commit 81e2073c175b ("genirq: Disable interrupts for force
threaded handlers") interrupt handlers always run with interrupts
disabled on non-RT so that drivers no longer need to do handle this.

So we're breaking RT knowingly here? If this is the case I'm not happy
with your change. (And if RT is not affected a different wording would
be good.)

Which wording, could you be more specific? It looks good from here and
no, RT is not affected.

The commit log says essentially: "The change is fine on non-RT" which
suggests there is a problem on RT.

I don't think you can read that into the commit message.

From a strictly logically point of view you indeed cannot. But if you go
to the street and say to people there that they can park their car in
this street free of charge between Monday and Friday, I expect that most
of them will assume that they have to pay for parking on weekends.

That analogy would almost seem to suggest bad intent on my side.

To say that this workaround is no longer needed on !RT does not imply
that it is needed on RT. If anything it suggests I have considered RT,
I'd say.

So when you said that on on-RT the reason why it used to need a
workaround is gone made me wonder what that implies for RT.

Fair enough. I thought it was obvious from the commit message and the
commits referred to, and that RT wouldn't depend on patching random
mainline drivers like this without a clear marking such as using raw
spin locks.

Greg's already picked this one up and this is hopefully the last one
we'll see of these.

Johan