coroutine: move into libqemuutil.a library

The coroutine files are currently referenced by the block-obj-y
variable. The coroutine functionality though is already used by
more than just the block code. eg migration code uses coroutine
yield. In the future the I/O channel code will also use the
coroutine yield functionality. Since the coroutine code is nicely
self-contained it can be easily built as part of the libqemuutil.a
library, making it widely available.

The headers are also moved into include/qemu, instead of the
include/block directory, since they are now part of the util
codebase, and the impl was never in the block/ directory
either.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

2 files changed, 273 insertions, 0 deletions

diff --git a/include/qemu/coroutine.h b/include/qemu/coroutine.h
new file mode 100644
index 0000000..20c027a
--- /dev/null
+++ b/include/qemu/coroutine.h
@@ -0,0 +1,219 @@
+/*
+ * QEMU coroutine implementation
+ *
+ * Copyright IBM, Corp. 2011
+ *
+ * Authors:
+ *  Stefan Hajnoczi    <stefanha@linux.vnet.ibm.com>
+ *  Kevin Wolf         <kwolf@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2 or later.
+ * See the COPYING.LIB file in the top-level directory.
+ *
+ */
+
+#ifndef QEMU_COROUTINE_H
+#define QEMU_COROUTINE_H
+
+#include <stdbool.h>
+#include "qemu/typedefs.h"
+#include "qemu/queue.h"
+#include "qemu/timer.h"
+
+/**
+ * Coroutines are a mechanism for stack switching and can be used for
+ * cooperative userspace threading.  These functions provide a simple but
+ * useful flavor of coroutines that is suitable for writing sequential code,
+ * rather than callbacks, for operations that need to give up control while
+ * waiting for events to complete.
+ *
+ * These functions are re-entrant and may be used outside the global mutex.
+ */
+
+/**
+ * Mark a function that executes in coroutine context
+ *
+ * Functions that execute in coroutine context cannot be called directly from
+ * normal functions.  In the future it would be nice to enable compiler or
+ * static checker support for catching such errors.  This annotation might make
+ * it possible and in the meantime it serves as documentation.
+ *
+ * For example:
+ *
+ *   static void coroutine_fn foo(void) {
+ *       ....
+ *   }
+ */
+#define coroutine_fn
+
+typedef struct Coroutine Coroutine;
+
+/**
+ * Coroutine entry point
+ *
+ * When the coroutine is entered for the first time, opaque is passed in as an
+ * argument.
+ *
+ * When this function returns, the coroutine is destroyed automatically and
+ * execution continues in the caller who last entered the coroutine.
+ */
+typedef void coroutine_fn CoroutineEntry(void *opaque);
+
+/**
+ * Create a new coroutine
+ *
+ * Use qemu_coroutine_enter() to actually transfer control to the coroutine.
+ */
+Coroutine *qemu_coroutine_create(CoroutineEntry *entry);
+
+/**
+ * Transfer control to a coroutine
+ *
+ * The opaque argument is passed as the argument to the entry point when
+ * entering the coroutine for the first time.  It is subsequently ignored.
+ */
+void qemu_coroutine_enter(Coroutine *coroutine, void *opaque);
+
+/**
+ * Transfer control back to a coroutine's caller
+ *
+ * This function does not return until the coroutine is re-entered using
+ * qemu_coroutine_enter().
+ */
+void coroutine_fn qemu_coroutine_yield(void);
+
+/**
+ * Get the currently executing coroutine
+ */
+Coroutine *coroutine_fn qemu_coroutine_self(void);
+
+/**
+ * Return whether or not currently inside a coroutine
+ *
+ * This can be used to write functions that work both when in coroutine context
+ * and when not in coroutine context.  Note that such functions cannot use the
+ * coroutine_fn annotation since they work outside coroutine context.
+ */
+bool qemu_in_coroutine(void);
+
+
+
+/**
+ * CoQueues are a mechanism to queue coroutines in order to continue executing
+ * them later. They provide the fundamental primitives on which coroutine locks
+ * are built.
+ */
+typedef struct CoQueue {
+    QTAILQ_HEAD(, Coroutine) entries;
+} CoQueue;
+
+/**
+ * Initialise a CoQueue. This must be called before any other operation is used
+ * on the CoQueue.
+ */
+void qemu_co_queue_init(CoQueue *queue);
+
+/**
+ * Adds the current coroutine to the CoQueue and transfers control to the
+ * caller of the coroutine.
+ */
+void coroutine_fn qemu_co_queue_wait(CoQueue *queue);
+
+/**
+ * Restarts the next coroutine in the CoQueue and removes it from the queue.
+ *
+ * Returns true if a coroutine was restarted, false if the queue is empty.
+ */
+bool coroutine_fn qemu_co_queue_next(CoQueue *queue);
+
+/**
+ * Restarts all coroutines in the CoQueue and leaves the queue empty.
+ */
+void coroutine_fn qemu_co_queue_restart_all(CoQueue *queue);
+
+/**
+ * Enter the next coroutine in the queue
+ */
+bool qemu_co_enter_next(CoQueue *queue);
+
+/**
+ * Checks if the CoQueue is empty.
+ */
+bool qemu_co_queue_empty(CoQueue *queue);
+
+
+/**
+ * Provides a mutex that can be used to synchronise coroutines
+ */
+typedef struct CoMutex {
+    bool locked;
+    CoQueue queue;
+} CoMutex;
+
+/**
+ * Initialises a CoMutex. This must be called before any other operation is used
+ * on the CoMutex.
+ */
+void qemu_co_mutex_init(CoMutex *mutex);
+
+/**
+ * Locks the mutex. If the lock cannot be taken immediately, control is
+ * transferred to the caller of the current coroutine.
+ */
+void coroutine_fn qemu_co_mutex_lock(CoMutex *mutex);
+
+/**
+ * Unlocks the mutex and schedules the next coroutine that was waiting for this
+ * lock to be run.
+ */
+void coroutine_fn qemu_co_mutex_unlock(CoMutex *mutex);
+
+typedef struct CoRwlock {
+    bool writer;
+    int reader;
+    CoQueue queue;
+} CoRwlock;
+
+/**
+ * Initialises a CoRwlock. This must be called before any other operation
+ * is used on the CoRwlock
+ */
+void qemu_co_rwlock_init(CoRwlock *lock);
+
+/**
+ * Read locks the CoRwlock. If the lock cannot be taken immediately because
+ * of a parallel writer, control is transferred to the caller of the current
+ * coroutine.
+ */
+void qemu_co_rwlock_rdlock(CoRwlock *lock);
+
+/**
+ * Write Locks the mutex. If the lock cannot be taken immediately because
+ * of a parallel reader, control is transferred to the caller of the current
+ * coroutine.
+ */
+void qemu_co_rwlock_wrlock(CoRwlock *lock);
+
+/**
+ * Unlocks the read/write lock and schedules the next coroutine that was
+ * waiting for this lock to be run.
+ */
+void qemu_co_rwlock_unlock(CoRwlock *lock);
+
+/**
+ * Yield the coroutine for a given duration
+ *
+ * Behaves similarly to co_sleep_ns(), but the sleeping coroutine will be
+ * resumed when using aio_poll().
+ */
+void coroutine_fn co_aio_sleep_ns(AioContext *ctx, QEMUClockType type,
+                                  int64_t ns);
+
+/**
+ * Yield until a file descriptor becomes readable
+ *
+ * Note that this function clobbers the handlers for the file descriptor.
+ */
+void coroutine_fn yield_until_fd_readable(int fd);
+
+#endif /* QEMU_COROUTINE_H */
diff --git a/include/qemu/coroutine_int.h b/include/qemu/coroutine_int.h
new file mode 100644
index 0000000..42d6838
--- /dev/null
+++ b/include/qemu/coroutine_int.h
@@ -0,0 +1,54 @@
+/*
+ * Coroutine internals
+ *
+ * Copyright (c) 2011 Kevin Wolf <kwolf@redhat.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#ifndef QEMU_COROUTINE_INT_H
+#define QEMU_COROUTINE_INT_H
+
+#include "qemu/queue.h"
+#include "qemu/coroutine.h"
+
+typedef enum {
+    COROUTINE_YIELD = 1,
+    COROUTINE_TERMINATE = 2,
+    COROUTINE_ENTER = 3,
+} CoroutineAction;
+
+struct Coroutine {
+    CoroutineEntry *entry;
+    void *entry_arg;
+    Coroutine *caller;
+    QSLIST_ENTRY(Coroutine) pool_next;
+
+    /* Coroutines that should be woken up when we yield or terminate */
+    QTAILQ_HEAD(, Coroutine) co_queue_wakeup;
+    QTAILQ_ENTRY(Coroutine) co_queue_next;
+};
+
+Coroutine *qemu_coroutine_new(void);
+void qemu_coroutine_delete(Coroutine *co);
+CoroutineAction qemu_coroutine_switch(Coroutine *from, Coroutine *to,
+                                      CoroutineAction action);
+void coroutine_fn qemu_co_queue_run_restart(Coroutine *co);
+
+#endif