diff mbox series

[2/2] util/async: print leaked BH name when AioContext finalizes

Message ID 20210414200247.917496-3-stefanha@redhat.com
State New
Headers show
Series util/async: print leaked BH name when AioContext finalizes | expand

Commit Message

Stefan Hajnoczi April 14, 2021, 8:02 p.m. UTC 
BHs must be deleted before the AioContext is finalized. If not, it's a
bug and probably indicates that some part of the program still expects
the BH to run in the future. That can lead to memory leaks, inconsistent
state, or just hangs.

Unfortunately the assert(flags & BH_DELETED) call in aio_ctx_finalize()
is difficult to debug because the assertion failure contains no
information about the BH!

Use the QEMUBH name field added in the previous patch to show a useful
error when a leaked BH is detected.

Suggested-by: Eric Ernst <eric.g.ernst@gmail.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 util/async.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/util/async.c b/util/async.c
index b6acb86520..2584fca249 100644
--- a/util/async.c
+++ b/util/async.c
@@ -344,8 +344,20 @@  aio_ctx_finalize(GSource     *source)
     assert(QSIMPLEQ_EMPTY(&ctx->bh_slice_list));
 
     while ((bh = aio_bh_dequeue(&ctx->bh_list, &flags))) {
-        /* qemu_bh_delete() must have been called on BHs in this AioContext */
-        assert(flags & BH_DELETED);
+        /*
+         * qemu_bh_delete() must have been called on BHs in this AioContext. In
+         * many cases memory leaks, hangs, or inconsistent state occur when a
+         * BH is leaked because something still expects it to run.
+         *
+         * If you hit this, fix the lifecycle of the BH so that
+         * qemu_bh_delete() and any associated cleanup is called before the
+         * AioContext is finalized.
+         */
+        if (unlikely(!(flags & BH_DELETED))) {
+            fprintf(stderr, "%s: BH '%s' leaked, aborting...\n",
+                    __func__, bh->name);
+            abort();
+        }
 
         g_free(bh);
     }