[PATCH v3 1/2] qio: Inherit follow_coroutine_ctx across TLS

[Eric Blake <eblake@redhat.com>]

Since qemu 8.2, the combination of NBD + TLS + iothread crashes on an
assertion failure:

qemu-kvm: ../io/channel.c:534: void qio_channel_restart_read(void *): Assertion `qemu_get_current_aio_context() == qemu_coroutine_get_aio_context(co)' failed.

It turns out that when we removed AioContext locking, we did so by
having NBD tell its qio channels that it wanted to opt in to
qio_channel_set_follow_coroutine_ctx(); but while we opted in on the
main channel, we did not opt in on the TLS wrapper channel.
qemu-iotests has coverage of NBD+iothread and NBD+TLS, but apparently
no coverage of NBD+TLS+iothread, or we would have noticed this
regression sooner.  (I'll add that in the next patch)

But while we could manually opt in to the TLS channel in nbd/server.c
(a one-line change), it is more generic if all qio channels that wrap
other channels inherit the follow status, in the same way that they
inherit feature bits.

CC: Stefan Hajnoczi <stefanha@redhat.com>
CC: Daniel P. Berrangé <berrange@redhat.com>
CC: qemu-stable@nongnu.org
Fixes: https://issues.redhat.com/browse/RHEL-34786
Fixes: 06e0f098 ("io: follow coroutine AioContext in qio_channel_yield()", v8.2.0)
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-ID: <20240518025246.791593-5-eblake@redhat.com>
---
 io/channel-tls.c     | 26 +++++++++++++++-----------
 io/channel-websock.c |  1 +
 2 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/io/channel-tls.c b/io/channel-tls.c
index 1d9c9c72bfb..67b97000060 100644
--- a/io/channel-tls.c
+++ b/io/channel-tls.c
@@ -69,37 +69,40 @@ qio_channel_tls_new_server(QIOChannel *master,
                            const char *aclname,
                            Error **errp)
 {
-    QIOChannelTLS *ioc;
+    QIOChannelTLS *tioc;
+    QIOChannel *ioc;

-    ioc = QIO_CHANNEL_TLS(object_new(TYPE_QIO_CHANNEL_TLS));
+    tioc = QIO_CHANNEL_TLS(object_new(TYPE_QIO_CHANNEL_TLS));
+    ioc = QIO_CHANNEL(tioc);

-    ioc->master = master;
+    tioc->master = master;
+    ioc->follow_coroutine_ctx = master->follow_coroutine_ctx;
     if (qio_channel_has_feature(master, QIO_CHANNEL_FEATURE_SHUTDOWN)) {
-        qio_channel_set_feature(QIO_CHANNEL(ioc), QIO_CHANNEL_FEATURE_SHUTDOWN);
+        qio_channel_set_feature(ioc, QIO_CHANNEL_FEATURE_SHUTDOWN);
     }
     object_ref(OBJECT(master));

-    ioc->session = qcrypto_tls_session_new(
+    tioc->session = qcrypto_tls_session_new(
         creds,
         NULL,
         aclname,
         QCRYPTO_TLS_CREDS_ENDPOINT_SERVER,
         errp);
-    if (!ioc->session) {
+    if (!tioc->session) {
         goto error;
     }

     qcrypto_tls_session_set_callbacks(
-        ioc->session,
+        tioc->session,
         qio_channel_tls_write_handler,
         qio_channel_tls_read_handler,
-        ioc);
+        tioc);

-    trace_qio_channel_tls_new_server(ioc, master, creds, aclname);
-    return ioc;
+    trace_qio_channel_tls_new_server(tioc, master, creds, aclname);
+    return tioc;

  error:
-    object_unref(OBJECT(ioc));
+    object_unref(OBJECT(tioc));
     return NULL;
 }

@@ -116,6 +119,7 @@ qio_channel_tls_new_client(QIOChannel *master,
     ioc = QIO_CHANNEL(tioc);

     tioc->master = master;
+    ioc->follow_coroutine_ctx = master->follow_coroutine_ctx;
     if (qio_channel_has_feature(master, QIO_CHANNEL_FEATURE_SHUTDOWN)) {
         qio_channel_set_feature(ioc, QIO_CHANNEL_FEATURE_SHUTDOWN);
     }
diff --git a/io/channel-websock.c b/io/channel-websock.c
index a12acc27cf2..de39f0d182d 100644
--- a/io/channel-websock.c
+++ b/io/channel-websock.c
@@ -883,6 +883,7 @@ qio_channel_websock_new_server(QIOChannel *master)
     ioc = QIO_CHANNEL(wioc);

     wioc->master = master;
+    ioc->follow_coroutine_ctx = master->follow_coroutine_ctx;
     if (qio_channel_has_feature(master, QIO_CHANNEL_FEATURE_SHUTDOWN)) {
         qio_channel_set_feature(ioc, QIO_CHANNEL_FEATURE_SHUTDOWN);
     }
-- 
2.45.1