On 17/04/21 16:36, Peter Xu wrote:
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>
This should be a better way to do the same:
----------- 8< ------------
From: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Subject: [PATCH] KVM: selftests: Wait for vcpu thread before signal setup
The main thread could start to send SIG_IPI at any time, even before signal
blocked on vcpu thread. Therefore, start the vcpu thread with the signal
blocked.
Without this patch, on very busy cores the dirty_log_test could fail directly
on receiving a SIGUSR1 without a handler (when vcpu runs far slower than main).
Reported-by: Peter Xu <peterx@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
diff --git a/tools/testing/selftests/kvm/dirty_log_test.c b/tools/testing/selftests/kvm/dirty_log_test.c
index ffa4e2791926..048973d50a45 100644
--- a/tools/testing/selftests/kvm/dirty_log_test.c
+++ b/tools/testing/selftests/kvm/dirty_log_test.c
@@ -527,9 +527,8 @@ static void *vcpu_worker(void *data)
*/
sigmask->len = 8;
pthread_sigmask(0, NULL, sigset);
+ sigdelset(sigset, SIG_IPI);
vcpu_ioctl(vm, VCPU_ID, KVM_SET_SIGNAL_MASK, sigmask);
- sigaddset(sigset, SIG_IPI);
- pthread_sigmask(SIG_BLOCK, sigset, NULL);
sigemptyset(sigset);
sigaddset(sigset, SIG_IPI);
@@ -858,6 +857,7 @@ int main(int argc, char *argv[])
.interval = TEST_HOST_LOOP_INTERVAL,
};
int opt, i;
+ sigset_t sigset;
sem_init(&sem_vcpu_stop, 0, 0);
sem_init(&sem_vcpu_cont, 0, 0);
@@ -916,6 +916,11 @@ int main(int argc, char *argv[])
srandom(time(0));
+ /* Ensure that vCPU threads start with SIG_IPI blocked. */
+ sigemptyset(&sigset);
+ sigaddset(&sigset, SIG_IPI);
+ pthread_sigmask(SIG_BLOCK, sigset, NULL);
+
if (host_log_mode_option == LOG_MODE_ALL) {
/* Run each log mode */
for (i = 0; i < LOG_MODE_NUM; i++) {
---
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);
