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>

4 files changed, 49 insertions, 4 deletions

diff --git a/include/block/aio.h b/include/block/aio.h
index ec8c5af642..5f342267d5 100644
--- a/include/block/aio.h
+++ b/include/block/aio.h
@@ -17,6 +17,7 @@
 #ifdef CONFIG_LINUX_IO_URING
 #include <liburing.h>
 #endif
+#include "qemu/coroutine.h"
 #include "qemu/queue.h"
 #include "qemu/event_notifier.h"
 #include "qemu/thread.h"
@@ -655,6 +656,15 @@ static inline bool aio_node_check(AioContext *ctx, bool is_external)
 void aio_co_schedule(AioContext *ctx, struct Coroutine *co);
 
 /**
+ * aio_co_reschedule_self:
+ * @new_ctx: the new context
+ *
+ * Move the currently running coroutine to new_ctx. If the coroutine is already
+ * running in new_ctx, do nothing.
+ */
+void coroutine_fn aio_co_reschedule_self(AioContext *new_ctx);
+
+/**
  * aio_co_wake:
  * @co: the coroutine
  *
diff --git a/include/block/block.h b/include/block/block.h
index ce2ac39299..d16c401cb4 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -641,6 +641,37 @@ bool bdrv_debug_is_suspended(BlockDriverState *bs, const char *tag);
 AioContext *bdrv_get_aio_context(BlockDriverState *bs);
 
 /**
+ * Move the current coroutine to the AioContext of @bs and return the old
+ * AioContext of the coroutine. Increase bs->in_flight so that draining @bs
+ * will wait for the operation to proceed until the corresponding
+ * bdrv_co_leave().
+ *
+ * Consequently, you can't call drain inside a bdrv_co_enter/leave() section as
+ * this will deadlock.
+ */
+AioContext *coroutine_fn bdrv_co_enter(BlockDriverState *bs);
+
+/**
+ * Ends a section started by bdrv_co_enter(). Move the current coroutine back
+ * to old_ctx and decrease bs->in_flight again.
+ */
+void coroutine_fn bdrv_co_leave(BlockDriverState *bs, AioContext *old_ctx);
+
+/**
+ * Locks the AioContext of @bs if it's not the current AioContext. This avoids
+ * double locking which could lead to deadlocks: This is a coroutine_fn, so we
+ * know we already own the lock of the current AioContext.
+ *
+ * May only be called in the main thread.
+ */
+void coroutine_fn bdrv_co_lock(BlockDriverState *bs);
+
+/**
+ * Unlocks the AioContext of @bs if it's not the current AioContext.
+ */
+void coroutine_fn bdrv_co_unlock(BlockDriverState *bs);
+
+/**
  * Transfer control to @co in the aio context of @bs
  */
 void bdrv_coroutine_enter(BlockDriverState *bs, Coroutine *co);
diff --git a/include/monitor/monitor.h b/include/monitor/monitor.h
index c0170773d4..348bfad3d5 100644
--- a/include/monitor/monitor.h
+++ b/include/monitor/monitor.h
@@ -5,7 +5,6 @@
 #include "qapi/qapi-types-misc.h"
 #include "qemu/readline.h"
 
-extern __thread Monitor *cur_mon;
 typedef struct MonitorHMP MonitorHMP;
 typedef struct MonitorOptions MonitorOptions;
 
@@ -13,6 +12,8 @@ typedef struct MonitorOptions MonitorOptions;
 
 extern QemuOptsList qemu_mon_opts;
 
+Monitor *monitor_cur(void);
+Monitor *monitor_set_cur(Coroutine *co, Monitor *mon);
 bool monitor_cur_is_qmp(void);
 
 void monitor_init_globals(void);
@@ -33,8 +34,8 @@ int monitor_vprintf(Monitor *mon, const char *fmt, va_list ap)
     GCC_FMT_ATTR(2, 0);
 int monitor_printf(Monitor *mon, const char *fmt, ...) GCC_FMT_ATTR(2, 3);
 void monitor_flush(Monitor *mon);
-int monitor_set_cpu(int cpu_index);
-int monitor_get_cpu_index(void);
+int monitor_set_cpu(Monitor *mon, int cpu_index);
+int monitor_get_cpu_index(Monitor *mon);
 
 void monitor_read_command(MonitorHMP *mon, int show_prompt);
 int monitor_read_password(MonitorHMP *mon, ReadLineFunc *readline_func,
diff --git a/include/qapi/qmp/dispatch.h b/include/qapi/qmp/dispatch.h
index 5a9cf82472..af8d96c570 100644
--- a/include/qapi/qmp/dispatch.h
+++ b/include/qapi/qmp/dispatch.h
@@ -14,6 +14,7 @@
 #ifndef QAPI_QMP_DISPATCH_H
 #define QAPI_QMP_DISPATCH_H
 
+#include "monitor/monitor.h"
 #include "qemu/queue.h"
 
 typedef void (QmpCommandFunc)(QDict *, QObject **, Error **);
@@ -24,11 +25,13 @@ typedef enum QmpCommandOptions
     QCO_NO_SUCCESS_RESP       =  (1U << 0),
     QCO_ALLOW_OOB             =  (1U << 1),
     QCO_ALLOW_PRECONFIG       =  (1U << 2),
+    QCO_COROUTINE             =  (1U << 3),
 } QmpCommandOptions;
 
 typedef struct QmpCommand
 {
     const char *name;
+    /* Runs in coroutine context if QCO_COROUTINE is set */
     QmpCommandFunc *fn;
     QmpCommandOptions options;
     QTAILQ_ENTRY(QmpCommand) node;
@@ -49,7 +52,7 @@ const char *qmp_command_name(const QmpCommand *cmd);
 bool qmp_has_success_response(const QmpCommand *cmd);
 QDict *qmp_error_response(Error *err);
 QDict *qmp_dispatch(const QmpCommandList *cmds, QObject *request,
-                    bool allow_oob);
+                    bool allow_oob, Monitor *cur_mon);
 bool qmp_is_oob(const QDict *dict);
 
 typedef void (*qmp_cmd_callback_fn)(const QmpCommand *cmd, void *opaque);