util/async: add a human-readable name to BHs for debugging
It can be difficult to debug issues with BHs in production environments.
Although BHs can usually be identified by looking up their ->cb()
function pointer, this requires debug information for the program. It is
also not possible to print human-readable diagnostics about BHs because
they have no identifier.
This patch adds a name to each BH. The name is not unique per instance
but differentiates between cb() functions, which is usually enough. It's
done by changing aio_bh_new() and friends to macros that stringify cb.
The next patch will use the name field when reporting leaked BHs.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20210414200247.917496-2-stefanha@redhat.com>
diff --git a/include/block/aio.h b/include/block/aio.h
index 10fcae1..807edce 100644
--- a/include/block/aio.h
+++ b/include/block/aio.h
@@ -292,19 +292,44 @@
void aio_context_release(AioContext *ctx);
/**
- * aio_bh_schedule_oneshot: Allocate a new bottom half structure that will run
- * only once and as soon as possible.
+ * aio_bh_schedule_oneshot_full: Allocate a new bottom half structure that will
+ * run only once and as soon as possible.
+ *
+ * @name: A human-readable identifier for debugging purposes.
*/
-void aio_bh_schedule_oneshot(AioContext *ctx, QEMUBHFunc *cb, void *opaque);
+void aio_bh_schedule_oneshot_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque,
+ const char *name);
/**
- * aio_bh_new: Allocate a new bottom half structure.
+ * aio_bh_schedule_oneshot: Allocate a new bottom half structure that will run
+ * only once and as soon as possible.
+ *
+ * A convenience wrapper for aio_bh_schedule_oneshot_full() that uses cb as the
+ * name string.
+ */
+#define aio_bh_schedule_oneshot(ctx, cb, opaque) \
+ aio_bh_schedule_oneshot_full((ctx), (cb), (opaque), (stringify(cb)))
+
+/**
+ * aio_bh_new_full: Allocate a new bottom half structure.
*
* Bottom halves are lightweight callbacks whose invocation is guaranteed
* to be wait-free, thread-safe and signal-safe. The #QEMUBH structure
* is opaque and must be allocated prior to its use.
+ *
+ * @name: A human-readable identifier for debugging purposes.
*/
-QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque);
+QEMUBH *aio_bh_new_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque,
+ const char *name);
+
+/**
+ * aio_bh_new: Allocate a new bottom half structure
+ *
+ * A convenience wrapper for aio_bh_new_full() that uses the cb as the name
+ * string.
+ */
+#define aio_bh_new(ctx, cb, opaque) \
+ aio_bh_new_full((ctx), (cb), (opaque), (stringify(cb)))
/**
* aio_notify: Force processing of pending events.
