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, 30 insertions, 0 deletions

diff --git a/util/async.c b/util/async.c
index f758354c6a..674dbefb7c 100644
--- a/util/async.c
+++ b/util/async.c
@@ -569,6 +569,36 @@ void aio_co_schedule(AioContext *ctx, Coroutine *co)
     aio_context_unref(ctx);
 }
 
+typedef struct AioCoRescheduleSelf {
+    Coroutine *co;
+    AioContext *new_ctx;
+} AioCoRescheduleSelf;
+
+static void aio_co_reschedule_self_bh(void *opaque)
+{
+    AioCoRescheduleSelf *data = opaque;
+    aio_co_schedule(data->new_ctx, data->co);
+}
+
+void coroutine_fn aio_co_reschedule_self(AioContext *new_ctx)
+{
+    AioContext *old_ctx = qemu_get_current_aio_context();
+
+    if (old_ctx != new_ctx) {
+        AioCoRescheduleSelf data = {
+            .co = qemu_coroutine_self(),
+            .new_ctx = new_ctx,
+        };
+        /*
+         * We can't directly schedule the coroutine in the target context
+         * because this would be racy: The other thread could try to enter the
+         * coroutine before it has yielded in this one.
+         */
+        aio_bh_schedule_oneshot(old_ctx, aio_co_reschedule_self_bh, &data);
+        qemu_coroutine_yield();
+    }
+}
+
 void aio_co_wake(struct Coroutine *co)
 {
     AioContext *ctx;