[PATCH v3] erofs-utils: fix thread join loop in erofs_destroy_workqueue

[Nithurshen]

Currently, `erofs_destroy_workqueue` returns immediately if a single
`pthread_join` fails. However, it does not log the failure, making it
difficult to debug if a worker thread gets stuck.

Add an error log when `pthread_join` fails. Retain the early return
behavior to safely abort the teardown process, ensuring we do not
free the synchronization primitives and worker array while threads
are potentially still alive (avoiding a use after free).

Signed-off-by: Nithurshen <nithurshen.dev at gmail.com>
---
 lib/workqueue.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/lib/workqueue.c b/lib/workqueue.c
index 18ee0f9..4a1a957 100644
--- a/lib/workqueue.c
+++ b/lib/workqueue.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0+ OR Apache-2.0
 #include <pthread.h>
 #include <stdlib.h>
+#include "erofs/print.h"
 #include "erofs/workqueue.h"
 
 static void *worker_thread(void *arg)
@@ -53,10 +54,14 @@ int erofs_destroy_workqueue(struct erofs_workqueue *wq)
 	while (wq->nworker) {
 		int ret = -pthread_join(wq->workers[wq->nworker - 1], NULL);
 
-		if (ret)
+		if (ret) {
+			erofs_err("failed to join worker thread %u: %d",
+				  wq->nworker - 1, ret);
 			return ret;
+		}
 		--wq->nworker;
 	}
+
 	free(wq->workers);
 	pthread_mutex_destroy(&wq->lock);
 	pthread_cond_destroy(&wq->cond_empty);
-- 
2.43.0