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| author | Joe Lawrence <joe.lawrence@redhat.com> | 2022-06-02 16:32:33 -0400 |
|---|---|---|
| committer | Petr Mladek <pmladek@suse.com> | 2022-06-15 10:29:10 +0200 |
| commit | 55eb9a6c8bf3e2099863118ef53e02d9f44f85a8 (patch) | |
| tree | 64a40e61665e62d2fa4c2d5b648611e34d6dd6fd /lib | |
| parent | 7c9e960c636306f632ccae623bf94b2b53d35cbd (diff) | |
| download | lwn-55eb9a6c8bf3e2099863118ef53e02d9f44f85a8.tar.gz lwn-55eb9a6c8bf3e2099863118ef53e02d9f44f85a8.zip | |
selftests/livepatch: better synchronize test_klp_callbacks_busy
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
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/livepatch/test_klp_callbacks_busy.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/lib/livepatch/test_klp_callbacks_busy.c b/lib/livepatch/test_klp_callbacks_busy.c index 7ac845f65be5..133929e0ce8f 100644 --- a/lib/livepatch/test_klp_callbacks_busy.c +++ b/lib/livepatch/test_klp_callbacks_busy.c @@ -16,10 +16,12 @@ MODULE_PARM_DESC(block_transition, "block_transition (default=false)"); static void busymod_work_func(struct work_struct *work); static DECLARE_WORK(work, busymod_work_func); +static DECLARE_COMPLETION(busymod_work_started); static void busymod_work_func(struct work_struct *work) { pr_info("%s enter\n", __func__); + complete(&busymod_work_started); while (READ_ONCE(block_transition)) { /* @@ -37,6 +39,12 @@ static int test_klp_callbacks_busy_init(void) pr_info("%s\n", __func__); schedule_work(&work); + /* + * To synchronize kernel messages, hold the init function from + * exiting until the work function's entry message has printed. + */ + wait_for_completion(&busymod_work_started); + if (!block_transition) { /* * Serialize output: print all messages from the work |