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[PATCH 24/77] aio-posix: don't duplicate fd handler deletion in fdmon_io

From: Michael Roth
Subject: [PATCH 24/77] aio-posix: don't duplicate fd handler deletion in fdmon_io_uring_destroy()
Date: Thu, 3 Sep 2020 15:58:42 -0500

From: Stefan Hajnoczi <stefanha@redhat.com>

The io_uring file descriptor monitoring implementation has an internal
list of fd handlers that are pending submission to io_uring.
fdmon_io_uring_destroy() deletes all fd handlers on the list.

Don't delete fd handlers directly in fdmon_io_uring_destroy() for two
1. This duplicates the aio-posix.c AioHandler deletion code and could
   become outdated if the struct changes.
2. Only handlers with the FDMON_IO_URING_REMOVE flag set are safe to
   remove. If the flag is not set then something still has a pointer to
   the fd handler. Let aio-posix.c and its user worry about that. In
   practice this isn't an issue because fdmon_io_uring_destroy() is only
   called when shutting down so all users have removed their fd
   handlers, but the next patch will need this!

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Tested-by: Oleksandr Natalenko <oleksandr@redhat.com>
Message-id: 20200511183630.279750-2-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
(cherry picked from commit de137e44f75d9868f5b548638081850f6ac771f2)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
 util/aio-posix.c      |  1 +
 util/fdmon-io_uring.c | 13 ++++++++++---
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/util/aio-posix.c b/util/aio-posix.c
index c3613d299e..8af334ab19 100644
--- a/util/aio-posix.c
+++ b/util/aio-posix.c
@@ -679,6 +679,7 @@ void aio_context_destroy(AioContext *ctx)
+    aio_free_deleted_handlers(ctx);
 void aio_context_set_poll_params(AioContext *ctx, int64_t max_ns,
diff --git a/util/fdmon-io_uring.c b/util/fdmon-io_uring.c
index d5a80ed6fb..1d14177df0 100644
--- a/util/fdmon-io_uring.c
+++ b/util/fdmon-io_uring.c
@@ -342,11 +342,18 @@ void fdmon_io_uring_destroy(AioContext *ctx)
-        /* No need to submit these anymore, just free them. */
+        /* Move handlers due to be removed onto the deleted list */
         while ((node = QSLIST_FIRST_RCU(&ctx->submit_list))) {
+            unsigned flags = atomic_fetch_and(&node->flags,
+                    ~(FDMON_IO_URING_PENDING |
+                      FDMON_IO_URING_ADD |
+                      FDMON_IO_URING_REMOVE));
+            if (flags & FDMON_IO_URING_REMOVE) {
+                QLIST_INSERT_HEAD_RCU(&ctx->deleted_aio_handlers, node, 
+            }
             QSLIST_REMOVE_HEAD_RCU(&ctx->submit_list, node_submitted);
-            QLIST_REMOVE(node, node);
-            g_free(node);
         ctx->fdmon_ops = &fdmon_poll_ops;

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