On 11.09.13 20:35, Steven Rostedt wrote:
On Wed, 11 Sep 2013 20:29:07 +0200
Mario Kleiner <mario.kleiner@xxxxxxxxxxxxxxxx> wrote:
That said, maybe preempt_disable is no longer the optimal choice there
and there's some better way to achieve good protection against
interruptions of that bit of code? My knowledge here is a bit rusty, and
the intel kms drivers and rt stuff has changed quite a bit.
If you set your code to a higher priority than other tasks (and
interrupts) than it wont be preempted there. Unless of course it blocks
on a lock, but even then, priority inheritance will take place and it
still should be rather quick. (unless the holder of the lock is doing
that strange polling).
-- Steve
Right, on a rt kernel. But that creates the problem of not very computer
savvy users (psychologists and biologists mostly) somehow having to
choose proper priorities for gpu interrupt threads and for the
x-server/wayland/..., and not much protection on a non-rt kernel?
preempt_disable() a few years ago looked like a good "plug and play"
default solution, because the ->get_crtc_scanoutpos() function was
supposed to have a very low and bounded execution time. At the time we
wrote the patches for intel/radeon/nouveau, that was the case. Typical
execution time (= preempt off time) was like 1-4 usecs, even on very low
end hardware.
Seems that at least intel's kms driver does a lot of things now, which
can sleep and spin inside that section? I tried to follow the posted
stack trace, but got lost somewhere around the i915_read32 code and
power management stuff...
-mario
--
To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
