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authorJoe Lawrence <joe.lawrence@redhat.com>2022-06-02 23:32:33 +0300
committerPetr Mladek <pmladek@suse.com>2022-06-15 11:29:10 +0300
commit55eb9a6c8bf3e2099863118ef53e02d9f44f85a8 (patch)
tree64a40e61665e62d2fa4c2d5b648611e34d6dd6fd /lib/livepatch
parent7c9e960c636306f632ccae623bf94b2b53d35cbd (diff)
downloadlinux-55eb9a6c8bf3e2099863118ef53e02d9f44f85a8.tar.xz
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/livepatch')
-rw-r--r--lib/livepatch/test_klp_callbacks_busy.c8
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