This is a note to let you know that I've just added the patch titled
selftests/livepatch: better synchronize test_klp_callbacks_busy
to the 5.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
selftests-livepatch-better-synchronize-test_klp_call.patch
and it can be found in the queue-5.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit f5723f277e8ece485fb626b13b829189d543003e
Author: Joe Lawrence <joe.lawrence@xxxxxxxxxx>
Date: Thu Jun 2 16:32:33 2022 -0400
selftests/livepatch: better synchronize test_klp_callbacks_busy
[ 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@xxxxxxxxxx>
Reviewed-by: Petr Mladek <pmladek@xxxxxxxx>
Signed-off-by: Petr Mladek <pmladek@xxxxxxxx>
Link: https://lore.kernel.org/r/20220602203233.979681-1-joe.lawrence@xxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
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
