FYI, we noticed the below changes on
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
commit 6224beb12e190ff11f3c7d4bf50cb2922878f600 ("tracing: Have branch tracer use
recursive field of task struct")
The commit fixed hang after Testing trace branch before. Which confused
our test system for quite some while.
Thanks,
Ying Huang