The coroutine then executes until it returns or yields:
void coroutine_fn my_coroutine(void *opaque) {
MyData *my_data = opaque;
/* do some work */
qemu_coroutine_yield();
/* do some more work */
}
Yielding switches control back to the caller of qemu_coroutine_enter().
This is typically used to switch back to the main thread's event loop
after issuing an asynchronous I/O request. The request callback will
then invoke qemu_coroutine_enter() once more to switch back to the
coroutine.
Note that coroutines never execute concurrently and should only be used
from threads which hold the global mutex. This restriction makes
programming with coroutines easier than with threads. Race conditions
cannot occur since only one coroutine may be active at any time. Other
coroutines can only run across yield.
This coroutines implementation is based on the gtk-vnc implementation
written by Anthony Liguori<address@hidden> but it has been
significantly rewritten by Kevin Wolf<address@hidden> to use
setjmp()/longjmp() instead of the more expensive swapcontext().
Signed-off-by: Kevin Wolf<address@hidden>
Signed-off-by: Stefan Hajnoczi<address@hidden>
---
Makefile.objs | 7 +++
coroutine-ucontext.c | 73 +++++++++++++++++++++++++++
coroutine-win32.c | 57 +++++++++++++++++++++
qemu-coroutine-int.h | 57 +++++++++++++++++++++
qemu-coroutine.c | 132 ++++++++++++++++++++++++++++++++++++++++++++++++++
qemu-coroutine.h | 82 +++++++++++++++++++++++++++++++
trace-events | 5 ++
7 files changed, 413 insertions(+), 0 deletions(-)
create mode 100644 coroutine-ucontext.c
create mode 100644 coroutine-win32.c
create mode 100644 qemu-coroutine-int.h
create mode 100644 qemu-coroutine.c
create mode 100644 qemu-coroutine.h
diff --git a/Makefile.objs b/Makefile.objs
index 9d8851e..cba6c2b 100644
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -11,6 +11,12 @@ oslib-obj-$(CONFIG_WIN32) += oslib-win32.o
oslib-obj-$(CONFIG_POSIX) += oslib-posix.o
#######################################################################
+# coroutines
+coroutine-obj-y = qemu-coroutine.o
+coroutine-obj-$(CONFIG_POSIX) += coroutine-ucontext.o
+coroutine-obj-$(CONFIG_WIN32) += coroutine-win32.o
+
+#######################################################################
# block-obj-y is code used by both qemu system emulation and qemu-img
block-obj-y = cutils.o cache-utils.o qemu-malloc.o qemu-option.o module.o
async.o
@@ -67,6 +73,7 @@ common-obj-y += readline.o console.o cursor.o qemu-error.o
common-obj-y += $(oslib-obj-y)
common-obj-$(CONFIG_WIN32) += os-win32.o
common-obj-$(CONFIG_POSIX) += os-posix.o
+common-obj-y += $(coroutine-obj-y)
common-obj-y += tcg-runtime.o host-utils.o
common-obj-y += irq.o ioport.o input.o
diff --git a/coroutine-ucontext.c b/coroutine-ucontext.c
new file mode 100644
index 0000000..97f2b35
--- /dev/null
+++ b/coroutine-ucontext.c
@@ -0,0 +1,73 @@
+/*
+ * ucontext coroutine initialization code
+ *
+ * Copyright (C) 2006 Anthony Liguori<address@hidden>
+ * Copyright (C) 2011 Kevin Wolf<address@hidden>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.0 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301
USA
+ */
+
+/* XXX Is there a nicer way to disable glibc's stack check for longjmp? */
+#ifdef _FORTIFY_SOURCE
+#undef _FORTIFY_SOURCE
+#endif
+#include<setjmp.h>
+#include<stdint.h>
+#include<ucontext.h>
+#include "qemu-coroutine-int.h"
+
+static Coroutine *new_coroutine;
+
+static void continuation_trampoline(void)
+{
+ Coroutine *co = new_coroutine;
+
+ /* Initialize longjmp environment and switch back to
+ * qemu_coroutine_init_env() in the old ucontext. */
+ if (!setjmp(co->env)) {
+ return;
+ }
+
+ while (true) {
+ co->entry(co->data);
+ if (!setjmp(co->env)) {
+ longjmp(co->caller->env, COROUTINE_TERMINATE);
+ }
+ }
+}
+
+int qemu_coroutine_init_env(Coroutine *co)
+{
+ ucontext_t old_uc, uc;
+
+ /* Create a new ucontext for switching to the coroutine stack and setting
+ * up a longjmp environment. */
+ if (getcontext(&uc) == -1) {
+ return -errno;
+ }
+
+ uc.uc_link =&old_uc;
+ uc.uc_stack.ss_sp = co->stack;
+ uc.uc_stack.ss_size = co->stack_size;
+ uc.uc_stack.ss_flags = 0;
+
+ new_coroutine = co;
+ makecontext(&uc, (void *)continuation_trampoline, 0);
+
+ /* Initialize the longjmp environment */
+ swapcontext(&old_uc,&uc);
+
+ return 0;
+}
diff --git a/coroutine-win32.c b/coroutine-win32.c
new file mode 100644
index 0000000..f4521c3
--- /dev/null
+++ b/coroutine-win32.c
@@ -0,0 +1,57 @@
+/*
+ * Win32 coroutine initialization code
+ *
+ * Copyright (c) 2011 Kevin Wolf<address@hidden>
+ *
+ * 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.
+ */
+
+#include "qemu-coroutine-int.h"
+
+static void __attribute__((used)) trampoline(Coroutine *co)
+{
+ if (!setjmp(co->env)) {
+ return;
+ }
+
+ while (true) {
+ co->entry(co->data);
+ if (!setjmp(co->env)) {
+ longjmp(co->caller->env, COROUTINE_TERMINATE);
+ }
+ }
+}
+
+int qemu_coroutine_init_env(Coroutine *co)
+{
+#ifdef __i386__
+ asm volatile(
+ "mov %%esp, %%ebx;"
+ "mov %0, %%esp;"
+ "pushl %1;"
+ "call _trampoline;"
+ "mov %%ebx, %%esp;"
+ : : "r" (co->stack + co->stack_size), "r" (co) : "ebx"
+ );