Merge remote-tracking branch 'remotes/armbru/tags/pull-monitor-2020-10-09' into staging

Monitor patches for 2020-10-09

# gpg: Signature made Fri 09 Oct 2020 06:16:51 BST
# gpg:                using RSA key 354BC8B3D7EB2A6B68674E5F3870B400EB918653
# gpg:                issuer "armbru@redhat.com"
# gpg: Good signature from "Markus Armbruster <armbru@redhat.com>" [full]
# gpg:                 aka "Markus Armbruster <armbru@pond.sub.org>" [full]
# Primary key fingerprint: 354B C8B3 D7EB 2A6B 6867  4E5F 3870 B400 EB91 8653

* remotes/armbru/tags/pull-monitor-2020-10-09:
  block: Convert 'block_resize' to coroutine
  block: Add bdrv_lock()/unlock()
  block: Add bdrv_co_enter()/leave()
  util/async: Add aio_co_reschedule_self()
  hmp: Add support for coroutine command handlers
  qmp: Move dispatcher to a coroutine
  qapi: Add a 'coroutine' flag for commands
  monitor: Make current monitor a per-coroutine property
  qmp: Call monitor_set_cur() only in qmp_dispatch()
  qmp: Assert that no other monitor is active
  hmp: Update current monitor only in handle_hmp_command()
  monitor: Use getter/setter functions for cur_mon
  monitor: Add Monitor parameter to monitor_get_cpu_index()
  monitor: Add Monitor parameter to monitor_set_cpu()

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 63 insertions, 2 deletions

diff --git a/qapi/qmp-dispatch.c b/qapi/qmp-dispatch.c
index 79347e0864..9a2d7dd29a 100644
--- a/qapi/qmp-dispatch.c
+++ b/qapi/qmp-dispatch.c
@@ -12,12 +12,16 @@
  */
 
 #include "qemu/osdep.h"
+
+#include "block/aio.h"
 #include "qapi/error.h"
 #include "qapi/qmp/dispatch.h"
 #include "qapi/qmp/qdict.h"
 #include "qapi/qmp/qjson.h"
 #include "sysemu/runstate.h"
 #include "qapi/qmp/qbool.h"
+#include "qemu/coroutine.h"
+#include "qemu/main-loop.h"
 
 static QDict *qmp_dispatch_check_obj(QDict *dict, bool allow_oob,
                                      Error **errp)
@@ -88,8 +92,32 @@ bool qmp_is_oob(const QDict *dict)
         && !qdict_haskey(dict, "execute");
 }
 
+typedef struct QmpDispatchBH {
+    const QmpCommand *cmd;
+    Monitor *cur_mon;
+    QDict *args;
+    QObject **ret;
+    Error **errp;
+    Coroutine *co;
+} QmpDispatchBH;
+
+static void do_qmp_dispatch_bh(void *opaque)
+{
+    QmpDispatchBH *data = opaque;
+
+    assert(monitor_cur() == NULL);
+    monitor_set_cur(qemu_coroutine_self(), data->cur_mon);
+    data->cmd->fn(data->args, data->ret, data->errp);
+    monitor_set_cur(qemu_coroutine_self(), NULL);
+    aio_co_wake(data->co);
+}
+
+/*
+ * Runs outside of coroutine context for OOB commands, but in coroutine
+ * context for everything else.
+ */
 QDict *qmp_dispatch(const QmpCommandList *cmds, QObject *request,
-                    bool allow_oob)
+                    bool allow_oob, Monitor *cur_mon)
 {
     Error *err = NULL;
     bool oob;
@@ -152,7 +180,40 @@ QDict *qmp_dispatch(const QmpCommandList *cmds, QObject *request,
         args = qdict_get_qdict(dict, "arguments");
         qobject_ref(args);
     }
-    cmd->fn(args, &ret, &err);
+
+    assert(!(oob && qemu_in_coroutine()));
+    assert(monitor_cur() == NULL);
+    if (!!(cmd->options & QCO_COROUTINE) == qemu_in_coroutine()) {
+        monitor_set_cur(qemu_coroutine_self(), cur_mon);
+        cmd->fn(args, &ret, &err);
+        monitor_set_cur(qemu_coroutine_self(), NULL);
+    } else {
+       /*
+        * Actual context doesn't match the one the command needs.
+        *
+        * Case 1: we are in coroutine context, but command does not
+        * have QCO_COROUTINE.  We need to drop out of coroutine
+        * context for executing it.
+        *
+        * Case 2: we are outside coroutine context, but command has
+        * QCO_COROUTINE.  Can't actually happen, because we get here
+        * outside coroutine context only when executing a command
+        * out of band, and OOB commands never have QCO_COROUTINE.
+        */
+        assert(!oob && qemu_in_coroutine() && !(cmd->options & QCO_COROUTINE));
+
+        QmpDispatchBH data = {
+            .cur_mon    = cur_mon,
+            .cmd        = cmd,
+            .args       = args,
+            .ret        = &ret,
+            .errp       = &err,
+            .co         = qemu_coroutine_self(),
+        };
+        aio_bh_schedule_oneshot(qemu_get_aio_context(), do_qmp_dispatch_bh,
+                                &data);
+        qemu_coroutine_yield();
+    }
     qobject_unref(args);
     if (err) {
         /* or assert(!ret) after reviewing all handlers: */