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49929f3ee8
[ Upstream commit 55eb9a6c8bf3e2099863118ef53e02d9f44f85a8 ]
The test_klp_callbacks_busy module conditionally blocks a future
livepatch transition by busy waiting inside its workqueue function,
busymod_work_func(). After scheduling this work, a test livepatch is
loaded, introducing the transition under test.
Both events are marked in the kernel log for later verification, but
there is no synchronization to ensure that busymod_work_func() logs its
function entry message before subsequent selftest commands log their own
messages. This can lead to a rare test failure due to unexpected
ordering like:
# --- expected
# +++ result
# @@ -1,7 +1,7 @@
# % modprobe test_klp_callbacks_busy block_transition=Y
# test_klp_callbacks_busy: test_klp_callbacks_busy_init
# -test_klp_callbacks_busy: busymod_work_func enter
# % modprobe test_klp_callbacks_demo
# +test_klp_callbacks_busy: busymod_work_func enter
# livepatch: enabling patch 'test_klp_callbacks_demo'
# livepatch: 'test_klp_callbacks_demo': initializing patching transition
# test_klp_callbacks_demo: pre_patch_callback: vmlinux
Force the module init function to wait until busymod_work_func() has
started (and logged its message), before exiting to the next selftest
steps.
Fixes: 547840bd5ae5 ("selftests/livepatch: simplify test-klp-callbacks busy target tests")
Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20220602203233.979681-1-joe.lawrence@redhat.com
Signed-off-by: Sasha Levin <sashal@kernel.org>