This is already fixed by 0f27b2b421a4 ("net: move xmit_recursion to
per-task variable on -RT"), which is in the various stable-rts too.
Apologies for the noise.

quoted

This also includes "543a589a00e8 net: xmit lock owner cleanup" from
v2.6.33.9-rt31 by mingo and tglx, which was just some cleanups to the
original patch which make porting to to current upstream easier.

Signed-off-by: Mark Beauchemin <redacted>
[ ported to latest upstream ]
Signed-off-by: Ingo Molnar <redacted>
Signed-off-by: Thomas Gleixner <redacted>
[ ported to 4.8 and used struct task_struct instead of void ]
Signed-off-by: Brian Silverman <redacted>

The signed-off-by chain suggest that Mark passed the patch to Ingo,
Thomas and to Brian. I doubt that. I can't resolve the sha1 id mentioned
here.

It's from the rt-history repository. The original commit in the
rt-history repository has that Signed-off-by chain except I added me
at the bottom. I guess it would make more sense to remove the other
people who just cherry-picked it if I run into this again.

Is this still broken as of v4.8-RT? I remember fixing something similar
with bridge devices.

Indeed you did it. It was cherry-picked to v4.1.19-rt22 too, which
matches the 4.1 kernel I originally found this on. I thought I checked
for the problem one or both of those, but apparently not... My bad.