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selftests/livepatch: better synchronize test_klp_callbacks_busy
[ Upstream commit55eb9a6c8b
] 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:547840bd5a
("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>
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@ -16,10 +16,12 @@ MODULE_PARM_DESC(block_transition, "block_transition (default=false)");
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static void busymod_work_func(struct work_struct *work);
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static DECLARE_WORK(work, busymod_work_func);
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static DECLARE_COMPLETION(busymod_work_started);
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static void busymod_work_func(struct work_struct *work)
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{
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pr_info("%s enter\n", __func__);
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complete(&busymod_work_started);
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while (READ_ONCE(block_transition)) {
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/*
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@ -37,6 +39,12 @@ static int test_klp_callbacks_busy_init(void)
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pr_info("%s\n", __func__);
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schedule_work(&work);
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/*
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* To synchronize kernel messages, hold the init function from
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* exiting until the work function's entry message has printed.
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*/
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wait_for_completion(&busymod_work_started);
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if (!block_transition) {
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/*
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* Serialize output: print all messages from the work
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