The main thread could start to send SIG_IPI at any time, even before signal
blocked on vcpu thread. Reuse the sem_vcpu_stop to sync on that, so when
SIG_IPI is sent the signal will always land correctly as an -EINTR.
Without this patch, on very busy cores the dirty_log_test could fail directly
on receiving a SIG_USR1 without a handler (when vcpu runs far slower than main).
Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
---
tools/testing/selftests/kvm/dirty_log_test.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/tools/testing/selftests/kvm/dirty_log_test.c b/tools/testing/selftests/kvm/dirty_log_test.c
index 510884f0eab8..25230e799bc4 100644
--- a/tools/testing/selftests/kvm/dirty_log_test.c
+++ b/tools/testing/selftests/kvm/dirty_log_test.c
@@ -534,6 +534,12 @@ static void *vcpu_worker(void *data)
sigemptyset(sigset);
sigaddset(sigset, SIG_IPI);
+ /*
+ * Tell the main thread that signals are setup already; let's borrow
+ * sem_vcpu_stop even if it's not for it.
+ */
+ sem_post(&sem_vcpu_stop);
+
guest_array = addr_gva2hva(vm, (vm_vaddr_t)random_array);
while (!READ_ONCE(host_quit)) {
@@ -785,6 +791,8 @@ static void run_test(enum vm_guest_mode mode, void *arg)
pthread_create(&vcpu_thread, NULL, vcpu_worker, vm);
+ sem_wait_until(&sem_vcpu_stop);
+
while (iteration < p->iterations) {
/* Give the vcpu thread some time to dirty some pages */
usleep(p->interval * 1000);
--
2.26.2
