Comment 0 for bug 1769027

Trying to run perf record ... --cgroup=mycgroup causes an immediate assertion failure:
refcount_inc: Assertion `!(!refcount_inc_not_zero(r))' failed.

Confirmed fixed by patching my linux-tools package with this upstream commit (on top of the commit in bug #1767204): https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit/tools/perf/util/cgroup.c?id=cd8dd032f61abeb08d2c03bab4968a9de231a1be