workqueue: forbid TEST_WORKQUEUE from being built-in

The benchmark drives the workqueue's affinity_scope through sysfs by
filp_open()'ing /sys/bus/workqueue/devices/bench_wq/affinity_scope. When
CONFIG_TEST_WORKQUEUE=y, the module_init runs during kernel init before
userspace has mounted sysfs, so every open returns -ENOENT and the
benchmark loop spins emitting:

  test_workqueue: open /sys/bus/workqueue/devices/bench_wq/affinity_scope failed: -2

Mirror the TEST_BPF pattern and add "depends on m" so Kconfig will not
let this be built into the kernel image, and document the reason in the
help text.

Fixes: 24b2e73f9700 ("workqueue: add test_workqueue benchmark module")
Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Tejun Heo <tj@kernel.org>

0 files changed, 0 insertions, 0 deletions