From 149020a75cf4a711db3d0fcd68b85b7deb0f3760 Mon Sep 17 00:00:00 2001
From: Stefan Hajnoczi <stefanha@redhat.com>
Date: Wed, 14 Apr 2021 21:02:46 +0100
Subject: [PATCH] util/async: add a human-readable name to BHs for debugging
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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>
Signed-off-by: liuxiangdong <liuxiangdong5@huawei.com>
---
 include/block/aio.h       | 31 ++++++++++++++++++++++++++++---
 include/qemu/main-loop.h  |  4 +++-
 tests/ptimer-test-stubs.c |  2 +-
 util/async.c              |  9 +++++++--
 util/main-loop.c          |  4 ++--
 5 files changed, 41 insertions(+), 9 deletions(-)

diff --git a/include/block/aio.h b/include/block/aio.h
index 9d28e247df..93b6c9b352 100644
--- a/include/block/aio.h
+++ b/include/block/aio.h
@@ -194,20 +194,45 @@ void aio_context_acquire(AioContext *ctx);
 /* Relinquish ownership of the AioContext. */
 void aio_context_release(AioContext *ctx);
 
+/**
+ * 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_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque,
+                                  const char *name);
+
 /**
  * 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.
  */
-void aio_bh_schedule_oneshot(AioContext *ctx, QEMUBHFunc *cb, void *opaque);
+#define aio_bh_schedule_oneshot(ctx, cb, opaque) \
+    aio_bh_schedule_oneshot_full((ctx), (cb), (opaque), (stringify(cb)))
 
 /**
- * aio_bh_new: Allocate a new bottom half structure.
+ * 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_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.
  */
-QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque);
+#define aio_bh_new(ctx, cb, opaque) \
+    aio_bh_new_full((ctx), (cb), (opaque), (stringify(cb)))
 
 /**
  * aio_notify: Force processing of pending events.
diff --git a/include/qemu/main-loop.h b/include/qemu/main-loop.h
index f6ba78ea73..b131a0edc5 100644
--- a/include/qemu/main-loop.h
+++ b/include/qemu/main-loop.h
@@ -299,7 +299,9 @@ void qemu_mutex_unlock_iothread(void);
 
 void qemu_fd_register(int fd);
 
-QEMUBH *qemu_bh_new(QEMUBHFunc *cb, void *opaque);
+#define qemu_bh_new(cb, opaque) \
+    qemu_bh_new_full((cb), (opaque), (stringify(cb)))
+QEMUBH *qemu_bh_new_full(QEMUBHFunc *cb, void *opaque, const char *name);
 void qemu_bh_schedule_idle(QEMUBH *bh);
 
 enum {
diff --git a/tests/ptimer-test-stubs.c b/tests/ptimer-test-stubs.c
index 54b3fd26f6..bc813c27b6 100644
--- a/tests/ptimer-test-stubs.c
+++ b/tests/ptimer-test-stubs.c
@@ -107,7 +107,7 @@ int64_t qemu_clock_deadline_ns_all(QEMUClockType type)
     return deadline;
 }
 
-QEMUBH *qemu_bh_new(QEMUBHFunc *cb, void *opaque)
+QEMUBH *qemu_bh_new_full(QEMUBHFunc *cb, void *opaque, const char *name)
 {
     QEMUBH *bh = g_new(QEMUBH, 1);
 
diff --git a/util/async.c b/util/async.c
index 5448e22dd1..77f6a791a7 100644
--- a/util/async.c
+++ b/util/async.c
@@ -38,6 +38,7 @@
 
 struct QEMUBH {
     AioContext *ctx;
+    const char *name;
     QEMUBHFunc *cb;
     void *opaque;
     QEMUBH *next;
@@ -46,7 +47,8 @@ struct QEMUBH {
     bool deleted;
 };
 
-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)
 {
     QEMUBH *bh;
     bh = g_new(QEMUBH, 1);
@@ -54,6 +56,7 @@ void aio_bh_schedule_oneshot(AioContext *ctx, QEMUBHFunc *cb, void *opaque)
         .ctx = ctx,
         .cb = cb,
         .opaque = opaque,
+        .name = name,
     };
     qemu_lockcnt_lock(&ctx->list_lock);
     bh->next = ctx->first_bh;
@@ -66,7 +69,8 @@ void aio_bh_schedule_oneshot(AioContext *ctx, QEMUBHFunc *cb, void *opaque)
     aio_notify(ctx);
 }
 
-QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque)
+QEMUBH *aio_bh_new_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque,
+                        const char *name)
 {
     QEMUBH *bh;
     bh = g_new(QEMUBH, 1);
@@ -74,6 +78,7 @@ QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque)
         .ctx = ctx,
         .cb = cb,
         .opaque = opaque,
+        .name = name,
     };
     qemu_lockcnt_lock(&ctx->list_lock);
     bh->next = ctx->first_bh;
diff --git a/util/main-loop.c b/util/main-loop.c
index e3eaa55866..382ceb8f8f 100644
--- a/util/main-loop.c
+++ b/util/main-loop.c
@@ -526,9 +526,9 @@ void main_loop_wait(int nonblocking)
 
 /* Functions to operate on the main QEMU AioContext.  */
 
-QEMUBH *qemu_bh_new(QEMUBHFunc *cb, void *opaque)
+QEMUBH *qemu_bh_new_full(QEMUBHFunc *cb, void *opaque, const char *name)
 {
-    return aio_bh_new(qemu_aio_context, cb, opaque);
+    return aio_bh_new_full(qemu_aio_context, cb, opaque, name);
 }
 
 /*
-- 
2.27.0

