From 023ca420ee3d4de76518d690afa98dcac33998ce Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Wed, 14 Apr 2021 21:02:47 +0100 Subject: [PATCH] util/async: print leaked BH name when AioContext finalizes 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 Signed-off-by: Stefan Hajnoczi Message-Id: <20210414200247.917496-3-stefanha@redhat.com> --- util/async.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/util/async.c b/util/async.c index 9a668996b8..9a41591319 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); } -- 2.11.4.GIT