From 3f2546b2ef55b661fd8dd69682b38992225e86f6 Mon Sep 17 00:00:00 2001
From: fishsoupisgood <github@madingley.org>
Date: Mon, 29 Apr 2019 01:17:54 +0100
Subject: Initial import of qemu-2.4.1

---
 qemu-coroutine.c | 146 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 146 insertions(+)
 create mode 100644 qemu-coroutine.c

(limited to 'qemu-coroutine.c')

diff --git a/qemu-coroutine.c b/qemu-coroutine.c
new file mode 100644
index 00000000..c17a92b1
--- /dev/null
+++ b/qemu-coroutine.c
@@ -0,0 +1,146 @@
+/*
+ * QEMU coroutines
+ *
+ * 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.
+ *
+ */
+
+#include "trace.h"
+#include "qemu-common.h"
+#include "qemu/thread.h"
+#include "qemu/atomic.h"
+#include "block/coroutine.h"
+#include "block/coroutine_int.h"
+
+enum {
+    POOL_BATCH_SIZE = 64,
+};
+
+/** Free list to speed up creation */
+static QSLIST_HEAD(, Coroutine) release_pool = QSLIST_HEAD_INITIALIZER(pool);
+static unsigned int release_pool_size;
+static __thread QSLIST_HEAD(, Coroutine) alloc_pool = QSLIST_HEAD_INITIALIZER(pool);
+static __thread unsigned int alloc_pool_size;
+static __thread Notifier coroutine_pool_cleanup_notifier;
+
+static void coroutine_pool_cleanup(Notifier *n, void *value)
+{
+    Coroutine *co;
+    Coroutine *tmp;
+
+    QSLIST_FOREACH_SAFE(co, &alloc_pool, pool_next, tmp) {
+        QSLIST_REMOVE_HEAD(&alloc_pool, pool_next);
+        qemu_coroutine_delete(co);
+    }
+}
+
+Coroutine *qemu_coroutine_create(CoroutineEntry *entry)
+{
+    Coroutine *co = NULL;
+
+    if (CONFIG_COROUTINE_POOL) {
+        co = QSLIST_FIRST(&alloc_pool);
+        if (!co) {
+            if (release_pool_size > POOL_BATCH_SIZE) {
+                /* Slow path; a good place to register the destructor, too.  */
+                if (!coroutine_pool_cleanup_notifier.notify) {
+                    coroutine_pool_cleanup_notifier.notify = coroutine_pool_cleanup;
+                    qemu_thread_atexit_add(&coroutine_pool_cleanup_notifier);
+                }
+
+                /* This is not exact; there could be a little skew between
+                 * release_pool_size and the actual size of release_pool.  But
+                 * it is just a heuristic, it does not need to be perfect.
+                 */
+                alloc_pool_size = atomic_xchg(&release_pool_size, 0);
+                QSLIST_MOVE_ATOMIC(&alloc_pool, &release_pool);
+                co = QSLIST_FIRST(&alloc_pool);
+            }
+        }
+        if (co) {
+            QSLIST_REMOVE_HEAD(&alloc_pool, pool_next);
+            alloc_pool_size--;
+        }
+    }
+
+    if (!co) {
+        co = qemu_coroutine_new();
+    }
+
+    co->entry = entry;
+    QTAILQ_INIT(&co->co_queue_wakeup);
+    return co;
+}
+
+static void coroutine_delete(Coroutine *co)
+{
+    co->caller = NULL;
+
+    if (CONFIG_COROUTINE_POOL) {
+        if (release_pool_size < POOL_BATCH_SIZE * 2) {
+            QSLIST_INSERT_HEAD_ATOMIC(&release_pool, co, pool_next);
+            atomic_inc(&release_pool_size);
+            return;
+        }
+        if (alloc_pool_size < POOL_BATCH_SIZE) {
+            QSLIST_INSERT_HEAD(&alloc_pool, co, pool_next);
+            alloc_pool_size++;
+            return;
+        }
+    }
+
+    qemu_coroutine_delete(co);
+}
+
+void qemu_coroutine_enter(Coroutine *co, void *opaque)
+{
+    Coroutine *self = qemu_coroutine_self();
+    CoroutineAction ret;
+
+    trace_qemu_coroutine_enter(self, co, opaque);
+
+    if (co->caller) {
+        fprintf(stderr, "Co-routine re-entered recursively\n");
+        abort();
+    }
+
+    co->caller = self;
+    co->entry_arg = opaque;
+    ret = qemu_coroutine_switch(self, co, COROUTINE_ENTER);
+
+    qemu_co_queue_run_restart(co);
+
+    switch (ret) {
+    case COROUTINE_YIELD:
+        return;
+    case COROUTINE_TERMINATE:
+        trace_qemu_coroutine_terminate(co);
+        coroutine_delete(co);
+        return;
+    default:
+        abort();
+    }
+}
+
+void coroutine_fn qemu_coroutine_yield(void)
+{
+    Coroutine *self = qemu_coroutine_self();
+    Coroutine *to = self->caller;
+
+    trace_qemu_coroutine_yield(self, to);
+
+    if (!to) {
+        fprintf(stderr, "Co-routine is yielding to no one\n");
+        abort();
+    }
+
+    self->caller = NULL;
+    qemu_coroutine_switch(self, to, COROUTINE_YIELD);
+}
-- 
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