@@ -15,7 +15,7 @@ oslib-obj-$(CONFIG_POSIX) += oslib-posix.o
block-obj-y = cutils.o cache-utils.o qemu-malloc.o qemu-option.o module.o
block-obj-y += nbd.o block.o aio.o aes.o qemu-config.o
-block-obj-$(CONFIG_POSIX) += posix-aio-compat.o
+block-obj-$(CONFIG_POSIX) += posix-aio-compat.o continuation.o coroutine_ucontext.o
block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
block-nested-y += raw.o cow.o qcow.o vdi.o vmdk.o cloop.o dmg.o bochs.o vpc.o vvfat.o
new file mode 100644
@@ -0,0 +1,87 @@
+/*
+ * GTK VNC Widget
+ *
+ * Copyright (C) 2006 Anthony Liguori <anthony@codemonkey.ws>
+ *
+ * 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
+ */
+
+#include "continuation.h"
+
+/*
+ * va_args to makecontext() must be type 'int', so passing
+ * the pointer we need may require several int args. This
+ * union is a quick hack to let us do that
+ */
+union cc_arg {
+ void *p;
+ int i[2];
+};
+
+static void continuation_trampoline(int i0, int i1)
+{
+ union cc_arg arg;
+ struct continuation *cc;
+ arg.i[0] = i0;
+ arg.i[1] = i1;
+ cc = arg.p;
+
+ cc->entry(cc);
+}
+
+int cc_init(struct continuation *cc)
+{
+ volatile union cc_arg arg;
+ arg.p = cc;
+ if (getcontext(&cc->uc) == -1)
+ return -1;
+
+ cc->uc.uc_link = &cc->last;
+ cc->uc.uc_stack.ss_sp = cc->stack;
+ cc->uc.uc_stack.ss_size = cc->stack_size;
+ cc->uc.uc_stack.ss_flags = 0;
+
+ makecontext(&cc->uc, (void *)continuation_trampoline, 2, arg.i[0], arg.i[1]);
+
+ return 0;
+}
+
+int cc_release(struct continuation *cc)
+{
+ if (cc->release)
+ return cc->release(cc);
+
+ return 0;
+}
+
+int cc_swap(struct continuation *from, struct continuation *to)
+{
+ to->exited = 0;
+ if (getcontext(&to->last) == -1)
+ return -1;
+ else if (to->exited == 0)
+ to->exited = 1;
+ else if (to->exited == 1)
+ return 1;
+
+ return swapcontext(&from->uc, &to->uc);
+}
+/*
+ * Local variables:
+ * c-indent-level: 8
+ * c-basic-offset: 8
+ * tab-width: 8
+ * End:
+ */
new file mode 100644
@@ -0,0 +1,58 @@
+/*
+ * GTK VNC Widget
+ *
+ * Copyright (C) 2006 Anthony Liguori <anthony@codemonkey.ws>
+ *
+ * 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
+ */
+
+#ifndef _CONTINUATION_H_
+#define _CONTINUATION_H_
+
+#include <ucontext.h>
+
+struct continuation
+{
+ char *stack;
+ size_t stack_size;
+ void (*entry)(struct continuation *cc);
+ int (*release)(struct continuation *cc);
+
+ /* private */
+ ucontext_t uc;
+ ucontext_t last;
+ int exited;
+};
+
+int cc_init(struct continuation *cc);
+
+int cc_release(struct continuation *cc);
+
+/* you can use an uninitialized struct continuation for from if you do not have
+ the current continuation handy. */
+int cc_swap(struct continuation *from, struct continuation *to);
+
+#define offset_of(type, member) ((unsigned long)(&((type *)0)->member))
+#define container_of(obj, type, member) \
+ (type *)(((char *)obj) - offset_of(type, member))
+
+#endif
+/*
+ * Local variables:
+ * c-indent-level: 8
+ * c-basic-offset: 8
+ * tab-width: 8
+ * End:
+ */
new file mode 100644
@@ -0,0 +1,72 @@
+/*
+ * GTK VNC Widget
+ *
+ * Copyright (C) 2006 Anthony Liguori <anthony@codemonkey.ws>
+ *
+ * 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
+ */
+
+#ifndef _COROUTINE_H_
+#define _COROUTINE_H_
+
+#define WITH_UCONTEXT 1
+
+#if WITH_UCONTEXT
+#include "continuation.h"
+#else
+#include <glib.h>
+#endif
+
+struct coroutine
+{
+ size_t stack_size;
+ void *(*entry)(void *);
+ int (*release)(struct coroutine *);
+
+ /* read-only */
+ int exited;
+
+ /* private */
+ struct coroutine *caller;
+ void *data;
+
+#if WITH_UCONTEXT
+ struct continuation cc;
+#else
+ GThread *thread;
+ gboolean runnable;
+#endif
+};
+
+int coroutine_init(struct coroutine *co);
+
+int coroutine_release(struct coroutine *co);
+
+void *coroutine_swap(struct coroutine *from, struct coroutine *to, void *arg);
+
+struct coroutine *coroutine_self(void);
+
+void *coroutine_yieldto(struct coroutine *to, void *arg);
+
+void *coroutine_yield(void *arg);
+
+#endif
+/*
+ * Local variables:
+ * c-indent-level: 8
+ * c-basic-offset: 8
+ * tab-width: 8
+ * End:
+ */
new file mode 100644
@@ -0,0 +1,131 @@
+/*
+ * GTK VNC Widget
+ *
+ * Copyright (C) 2006 Anthony Liguori <anthony@codemonkey.ws>
+ *
+ * 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
+ */
+
+#include <sys/types.h>
+#include <sys/mman.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include "coroutine.h"
+
+int coroutine_release(struct coroutine *co)
+{
+ return cc_release(&co->cc);
+}
+
+static int _coroutine_release(struct continuation *cc)
+{
+ struct coroutine *co = container_of(cc, struct coroutine, cc);
+
+ if (co->release) {
+ int ret = co->release(co);
+ if (ret < 0)
+ return ret;
+ }
+
+ co->caller = NULL;
+
+ return 0;
+}
+
+static void coroutine_trampoline(struct continuation *cc)
+{
+ struct coroutine *co = container_of(cc, struct coroutine, cc);
+ co->data = co->entry(co->data);
+}
+
+int coroutine_init(struct coroutine *co)
+{
+ if (co->stack_size == 0)
+ co->stack_size = 16 << 20;
+
+ co->cc.stack_size = co->stack_size;
+ co->cc.stack = mmap(0, co->stack_size,
+ PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS,
+ -1, 0);
+ if (co->cc.stack == MAP_FAILED)
+ return -1;
+ co->cc.entry = coroutine_trampoline;
+ co->cc.release = _coroutine_release;
+ co->exited = 0;
+
+ return cc_init(&co->cc);
+}
+
+#if 0
+static __thread struct coroutine leader;
+static __thread struct coroutine *current;
+#else
+static struct coroutine leader;
+static struct coroutine *current;
+#endif
+
+struct coroutine *coroutine_self(void)
+{
+ if (current == NULL)
+ current = &leader;
+ return current;
+}
+
+void *coroutine_swap(struct coroutine *from, struct coroutine *to, void *arg)
+{
+ int ret;
+ to->data = arg;
+ current = to;
+ ret = cc_swap(&from->cc, &to->cc);
+ if (ret == 0)
+ return from->data;
+ else if (ret == 1) {
+ coroutine_release(to);
+ current = &leader;
+ to->exited = 1;
+ return to->data;
+ }
+
+ return NULL;
+}
+
+void *coroutine_yieldto(struct coroutine *to, void *arg)
+{
+ if (to->caller) {
+ fprintf(stderr, "Co-routine is re-entering itself\n");
+ abort();
+ }
+ to->caller = coroutine_self();
+ return coroutine_swap(coroutine_self(), to, arg);
+}
+
+void *coroutine_yield(void *arg)
+{
+ struct coroutine *to = coroutine_self()->caller;
+ if (!to) {
+ fprintf(stderr, "Co-routine is yielding to no one\n");
+ abort();
+ }
+ coroutine_self()->caller = NULL;
+ return coroutine_swap(coroutine_self(), to, arg);
+}
+/*
+ * Local variables:
+ * c-indent-level: 8
+ * c-basic-offset: 8
+ * tab-width: 8
+ * End:
+ */
Asynchronous image format code is becoming very complex. Let's try using coroutines to write sequential code without callbacks but use coroutines to switch stacks under the hood. Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> --- Makefile.objs | 2 +- continuation.c | 87 +++++++++++++++++++++++++++++++++ continuation.h | 58 ++++++++++++++++++++++ coroutine.h | 72 +++++++++++++++++++++++++++ coroutine_ucontext.c | 131 ++++++++++++++++++++++++++++++++++++++++++++++++++ 5 files changed, 349 insertions(+), 1 deletions(-) create mode 100644 continuation.c create mode 100644 continuation.h create mode 100644 coroutine.h create mode 100644 coroutine_ucontext.c