devices: join worker threads in drop()

Make sure all devices join any threads they spawn before returning from
the drop() handler after signaling the exit event.

BUG=chromium:992494
TEST=crosvm exits without errors

Change-Id: I6bc91c32a08f568b041765044caa9aff6f7cf4a9
Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/1802156
Reviewed-by: Stephen Barber <smbarber@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>

1 files changed, 14 insertions, 3 deletions

diff --git a/devices/src/virtio/tpm.rs b/devices/src/virtio/tpm.rs
index e8c50f2..e7088ed 100644
--- a/devices/src/virtio/tpm.rs
+++ b/devices/src/virtio/tpm.rs
@@ -190,6 +190,7 @@ impl Worker {
 pub struct Tpm {
     storage: PathBuf,
     kill_evt: Option<EventFd>,
+    worker_thread: Option<thread::JoinHandle<()>>,
 }
 
 impl Tpm {
@@ -197,6 +198,7 @@ impl Tpm {
         Tpm {
             storage,
             kill_evt: None,
+            worker_thread: None,
         }
     }
 }
@@ -206,6 +208,10 @@ impl Drop for Tpm {
         if let Some(kill_evt) = self.kill_evt.take() {
             let _ = kill_evt.write(1);
         }
+
+        if let Some(worker_thread) = self.worker_thread.take() {
+            let _ = worker_thread.join();
+        }
     }
 }
 
@@ -271,9 +277,14 @@ impl VirtioDevice for Tpm {
             .name("virtio_tpm".to_string())
             .spawn(|| worker.run());
 
-        if let Err(e) = worker_result {
-            error!("vtpm failed to spawn virtio_tpm worker: {}", e);
-            return;
+        match worker_result {
+            Err(e) => {
+                error!("vtpm failed to spawn virtio_tpm worker: {}", e);
+                return;
+            }
+            Ok(join_handle) => {
+                self.worker_thread = Some(join_handle);
+            }
         }
     }
 }