[PATCH v2 1/3] rust_binder: never return 0 from next_debug_id

[Alice Ryhl <aliceryhl@google.com>]

Retry if fetch_add returns 0 in next_debug_id() so that valid debug IDs
start at 1 and 0 is never assigned, even if NEXT_DEBUG_ID wraps around.
This allows 0 to be used as a sentinel for an absent or uninitialized
debug_id (such as in TransactionInfo::to_node_debug_id and in
transaction log entries).

Assisted-by: LLM
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
---
 drivers/android/binder/rust_binder_main.rs | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/android/binder/rust_binder_main.rs b/drivers/android/binder/rust_binder_main.rs
index 955c4c348f73..bd26ef96fefb 100644
--- a/drivers/android/binder/rust_binder_main.rs
+++ b/drivers/android/binder/rust_binder_main.rs
@@ -98,7 +98,12 @@ fn default() -> Self {
 fn next_debug_id() -> usize {
     static NEXT_DEBUG_ID: Atomic<usize> = Atomic::new(0);
 
-    NEXT_DEBUG_ID.fetch_add(1, Relaxed)
+    loop {
+        let id = NEXT_DEBUG_ID.fetch_add(1, Relaxed);
+        if id != 0 {
+            return id;
+        }
+    }
 }
 
 /// Provides a single place to write Binder return values via the

-- 
2.56.0.rc1.315.gc6ed9934b7-goog