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>

9 files changed, 1253 insertions, 0 deletions

diff --git a/util/Makefile.objs b/util/Makefile.objs
index 114d6578c4..d8d7e7a919 100644
--- a/util/Makefile.objs
+++ b/util/Makefile.objs
@@ -18,3 +18,6 @@ util-obj-y += getauxval.o
 util-obj-y += readline.o
 util-obj-y += rfifolock.o
 util-obj-y += rcu.o
+util-obj-y += qemu-coroutine.o qemu-coroutine-lock.o qemu-coroutine-io.o
+util-obj-y += qemu-coroutine-sleep.o
+util-obj-y += coroutine-$(CONFIG_COROUTINE_BACKEND).o
diff --git a/util/coroutine-gthread.c b/util/coroutine-gthread.c
new file mode 100644
index 0000000000..0bcd77867d
--- /dev/null
+++ b/util/coroutine-gthread.c
@@ -0,0 +1,198 @@
+/*
+ * GThread coroutine initialization code
+ *
+ * Copyright (C) 2006  Anthony Liguori <anthony@codemonkey.ws>
+ * Copyright (C) 2011  Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
+ *
+ * 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, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <glib.h>
+#include "qemu-common.h"
+#include "qemu/coroutine_int.h"
+
+typedef struct {
+    Coroutine base;
+    GThread *thread;
+    bool runnable;
+    bool free_on_thread_exit;
+    CoroutineAction action;
+} CoroutineGThread;
+
+static CompatGMutex coroutine_lock;
+static CompatGCond coroutine_cond;
+
+/* GLib 2.31 and beyond deprecated various parts of the thread API,
+ * but the new interfaces are not available in older GLib versions
+ * so we have to cope with both.
+ */
+#if GLIB_CHECK_VERSION(2, 31, 0)
+/* Awkwardly, the GPrivate API doesn't provide a way to update the
+ * GDestroyNotify handler for the coroutine key dynamically. So instead
+ * we track whether or not the CoroutineGThread should be freed on
+ * thread exit / coroutine key update using the free_on_thread_exit
+ * field.
+ */
+static void coroutine_destroy_notify(gpointer data)
+{
+    CoroutineGThread *co = data;
+    if (co && co->free_on_thread_exit) {
+        g_free(co);
+    }
+}
+
+static GPrivate coroutine_key = G_PRIVATE_INIT(coroutine_destroy_notify);
+
+static inline CoroutineGThread *get_coroutine_key(void)
+{
+    return g_private_get(&coroutine_key);
+}
+
+static inline void set_coroutine_key(CoroutineGThread *co,
+                                     bool free_on_thread_exit)
+{
+    /* Unlike g_static_private_set() this does not call the GDestroyNotify
+     * if the previous value of the key was NULL. Fortunately we only need
+     * the GDestroyNotify in the non-NULL key case.
+     */
+    co->free_on_thread_exit = free_on_thread_exit;
+    g_private_replace(&coroutine_key, co);
+}
+
+static inline GThread *create_thread(GThreadFunc func, gpointer data)
+{
+    return g_thread_new("coroutine", func, data);
+}
+
+#else
+
+/* Handle older GLib versions */
+
+static GStaticPrivate coroutine_key = G_STATIC_PRIVATE_INIT;
+
+static inline CoroutineGThread *get_coroutine_key(void)
+{
+    return g_static_private_get(&coroutine_key);
+}
+
+static inline void set_coroutine_key(CoroutineGThread *co,
+                                     bool free_on_thread_exit)
+{
+    g_static_private_set(&coroutine_key, co,
+                         free_on_thread_exit ? (GDestroyNotify)g_free : NULL);
+}
+
+static inline GThread *create_thread(GThreadFunc func, gpointer data)
+{
+    return g_thread_create_full(func, data, 0, TRUE, TRUE,
+                                G_THREAD_PRIORITY_NORMAL, NULL);
+}
+
+#endif
+
+
+static void __attribute__((constructor)) coroutine_init(void)
+{
+#if !GLIB_CHECK_VERSION(2, 31, 0)
+    if (!g_thread_supported()) {
+        g_thread_init(NULL);
+    }
+#endif
+}
+
+static void coroutine_wait_runnable_locked(CoroutineGThread *co)
+{
+    while (!co->runnable) {
+        g_cond_wait(&coroutine_cond, &coroutine_lock);
+    }
+}
+
+static void coroutine_wait_runnable(CoroutineGThread *co)
+{
+    g_mutex_lock(&coroutine_lock);
+    coroutine_wait_runnable_locked(co);
+    g_mutex_unlock(&coroutine_lock);
+}
+
+static gpointer coroutine_thread(gpointer opaque)
+{
+    CoroutineGThread *co = opaque;
+
+    set_coroutine_key(co, false);
+    coroutine_wait_runnable(co);
+    co->base.entry(co->base.entry_arg);
+    qemu_coroutine_switch(&co->base, co->base.caller, COROUTINE_TERMINATE);
+    return NULL;
+}
+
+Coroutine *qemu_coroutine_new(void)
+{
+    CoroutineGThread *co;
+
+    co = g_malloc0(sizeof(*co));
+    co->thread = create_thread(coroutine_thread, co);
+    if (!co->thread) {
+        g_free(co);
+        return NULL;
+    }
+    return &co->base;
+}
+
+void qemu_coroutine_delete(Coroutine *co_)
+{
+    CoroutineGThread *co = DO_UPCAST(CoroutineGThread, base, co_);
+
+    g_thread_join(co->thread);
+    g_free(co);
+}
+
+CoroutineAction qemu_coroutine_switch(Coroutine *from_,
+                                      Coroutine *to_,
+                                      CoroutineAction action)
+{
+    CoroutineGThread *from = DO_UPCAST(CoroutineGThread, base, from_);
+    CoroutineGThread *to = DO_UPCAST(CoroutineGThread, base, to_);
+
+    g_mutex_lock(&coroutine_lock);
+    from->runnable = false;
+    from->action = action;
+    to->runnable = true;
+    to->action = action;
+    g_cond_broadcast(&coroutine_cond);
+
+    if (action != COROUTINE_TERMINATE) {
+        coroutine_wait_runnable_locked(from);
+    }
+    g_mutex_unlock(&coroutine_lock);
+    return from->action;
+}
+
+Coroutine *qemu_coroutine_self(void)
+{
+    CoroutineGThread *co = get_coroutine_key();
+    if (!co) {
+        co = g_malloc0(sizeof(*co));
+        co->runnable = true;
+        set_coroutine_key(co, true);
+    }
+
+    return &co->base;
+}
+
+bool qemu_in_coroutine(void)
+{
+    CoroutineGThread *co = get_coroutine_key();
+
+    return co && co->base.caller;
+}
diff --git a/util/coroutine-sigaltstack.c b/util/coroutine-sigaltstack.c
new file mode 100644
index 0000000000..39842a4a90
--- /dev/null
+++ b/util/coroutine-sigaltstack.c
@@ -0,0 +1,293 @@
+/*
+ * sigaltstack coroutine initialization code
+ *
+ * Copyright (C) 2006  Anthony Liguori <anthony@codemonkey.ws>
+ * Copyright (C) 2011  Kevin Wolf <kwolf@redhat.com>
+ * Copyright (C) 2012  Alex Barcelo <abarcelo@ac.upc.edu>
+** This file is partly based on pth_mctx.c, from the GNU Portable Threads
+**  Copyright (c) 1999-2006 Ralf S. Engelschall <rse@engelschall.com>
+ *
+ * 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 2.1 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, see <http://www.gnu.org/licenses/>.
+ */
+
+/* XXX Is there a nicer way to disable glibc's stack check for longjmp? */
+#ifdef _FORTIFY_SOURCE
+#undef _FORTIFY_SOURCE
+#endif
+#include <stdlib.h>
+#include <setjmp.h>
+#include <stdint.h>
+#include <pthread.h>
+#include <signal.h>
+#include "qemu-common.h"
+#include "qemu/coroutine_int.h"
+
+typedef struct {
+    Coroutine base;
+    void *stack;
+    sigjmp_buf env;
+} CoroutineUContext;
+
+/**
+ * Per-thread coroutine bookkeeping
+ */
+typedef struct {
+    /** Currently executing coroutine */
+    Coroutine *current;
+
+    /** The default coroutine */
+    CoroutineUContext leader;
+
+    /** Information for the signal handler (trampoline) */
+    sigjmp_buf tr_reenter;
+    volatile sig_atomic_t tr_called;
+    void *tr_handler;
+} CoroutineThreadState;
+
+static pthread_key_t thread_state_key;
+
+static CoroutineThreadState *coroutine_get_thread_state(void)
+{
+    CoroutineThreadState *s = pthread_getspecific(thread_state_key);
+
+    if (!s) {
+        s = g_malloc0(sizeof(*s));
+        s->current = &s->leader.base;
+        pthread_setspecific(thread_state_key, s);
+    }
+    return s;
+}
+
+static void qemu_coroutine_thread_cleanup(void *opaque)
+{
+    CoroutineThreadState *s = opaque;
+
+    g_free(s);
+}
+
+static void __attribute__((constructor)) coroutine_init(void)
+{
+    int ret;
+
+    ret = pthread_key_create(&thread_state_key, qemu_coroutine_thread_cleanup);
+    if (ret != 0) {
+        fprintf(stderr, "unable to create leader key: %s\n", strerror(errno));
+        abort();
+    }
+}
+
+/* "boot" function
+ * This is what starts the coroutine, is called from the trampoline
+ * (from the signal handler when it is not signal handling, read ahead
+ * for more information).
+ */
+static void coroutine_bootstrap(CoroutineUContext *self, Coroutine *co)
+{
+    /* Initialize longjmp environment and switch back the caller */
+    if (!sigsetjmp(self->env, 0)) {
+        siglongjmp(*(sigjmp_buf *)co->entry_arg, 1);
+    }
+
+    while (true) {
+        co->entry(co->entry_arg);
+        qemu_coroutine_switch(co, co->caller, COROUTINE_TERMINATE);
+    }
+}
+
+/*
+ * This is used as the signal handler. This is called with the brand new stack
+ * (thanks to sigaltstack). We have to return, given that this is a signal
+ * handler and the sigmask and some other things are changed.
+ */
+static void coroutine_trampoline(int signal)
+{
+    CoroutineUContext *self;
+    Coroutine *co;
+    CoroutineThreadState *coTS;
+
+    /* Get the thread specific information */
+    coTS = coroutine_get_thread_state();
+    self = coTS->tr_handler;
+    coTS->tr_called = 1;
+    co = &self->base;
+
+    /*
+     * Here we have to do a bit of a ping pong between the caller, given that
+     * this is a signal handler and we have to do a return "soon". Then the
+     * caller can reestablish everything and do a siglongjmp here again.
+     */
+    if (!sigsetjmp(coTS->tr_reenter, 0)) {
+        return;
+    }
+
+    /*
+     * Ok, the caller has siglongjmp'ed back to us, so now prepare
+     * us for the real machine state switching. We have to jump
+     * into another function here to get a new stack context for
+     * the auto variables (which have to be auto-variables
+     * because the start of the thread happens later). Else with
+     * PIC (i.e. Position Independent Code which is used when PTH
+     * is built as a shared library) most platforms would
+     * horrible core dump as experience showed.
+     */
+    coroutine_bootstrap(self, co);
+}
+
+Coroutine *qemu_coroutine_new(void)
+{
+    const size_t stack_size = 1 << 20;
+    CoroutineUContext *co;
+    CoroutineThreadState *coTS;
+    struct sigaction sa;
+    struct sigaction osa;
+    stack_t ss;
+    stack_t oss;
+    sigset_t sigs;
+    sigset_t osigs;
+    sigjmp_buf old_env;
+
+    /* The way to manipulate stack is with the sigaltstack function. We
+     * prepare a stack, with it delivering a signal to ourselves and then
+     * put sigsetjmp/siglongjmp where needed.
+     * This has been done keeping coroutine-ucontext as a model and with the
+     * pth ideas (GNU Portable Threads). See coroutine-ucontext for the basics
+     * of the coroutines and see pth_mctx.c (from the pth project) for the
+     * sigaltstack way of manipulating stacks.
+     */
+
+    co = g_malloc0(sizeof(*co));
+    co->stack = g_malloc(stack_size);
+    co->base.entry_arg = &old_env; /* stash away our jmp_buf */
+
+    coTS = coroutine_get_thread_state();
+    coTS->tr_handler = co;
+
+    /*
+     * Preserve the SIGUSR2 signal state, block SIGUSR2,
+     * and establish our signal handler. The signal will
+     * later transfer control onto the signal stack.
+     */
+    sigemptyset(&sigs);
+    sigaddset(&sigs, SIGUSR2);
+    pthread_sigmask(SIG_BLOCK, &sigs, &osigs);
+    sa.sa_handler = coroutine_trampoline;
+    sigfillset(&sa.sa_mask);
+    sa.sa_flags = SA_ONSTACK;
+    if (sigaction(SIGUSR2, &sa, &osa) != 0) {
+        abort();
+    }
+
+    /*
+     * Set the new stack.
+     */
+    ss.ss_sp = co->stack;
+    ss.ss_size = stack_size;
+    ss.ss_flags = 0;
+    if (sigaltstack(&ss, &oss) < 0) {
+        abort();
+    }
+
+    /*
+     * Now transfer control onto the signal stack and set it up.
+     * It will return immediately via "return" after the sigsetjmp()
+     * was performed. Be careful here with race conditions.  The
+     * signal can be delivered the first time sigsuspend() is
+     * called.
+     */
+    coTS->tr_called = 0;
+    pthread_kill(pthread_self(), SIGUSR2);
+    sigfillset(&sigs);
+    sigdelset(&sigs, SIGUSR2);
+    while (!coTS->tr_called) {
+        sigsuspend(&sigs);
+    }
+
+    /*
+     * Inform the system that we are back off the signal stack by
+     * removing the alternative signal stack. Be careful here: It
+     * first has to be disabled, before it can be removed.
+     */
+    sigaltstack(NULL, &ss);
+    ss.ss_flags = SS_DISABLE;
+    if (sigaltstack(&ss, NULL) < 0) {
+        abort();
+    }
+    sigaltstack(NULL, &ss);
+    if (!(oss.ss_flags & SS_DISABLE)) {
+        sigaltstack(&oss, NULL);
+    }
+
+    /*
+     * Restore the old SIGUSR2 signal handler and mask
+     */
+    sigaction(SIGUSR2, &osa, NULL);
+    pthread_sigmask(SIG_SETMASK, &osigs, NULL);
+
+    /*
+     * Now enter the trampoline again, but this time not as a signal
+     * handler. Instead we jump into it directly. The functionally
+     * redundant ping-pong pointer arithmetic is necessary to avoid
+     * type-conversion warnings related to the `volatile' qualifier and
+     * the fact that `jmp_buf' usually is an array type.
+     */
+    if (!sigsetjmp(old_env, 0)) {
+        siglongjmp(coTS->tr_reenter, 1);
+    }
+
+    /*
+     * Ok, we returned again, so now we're finished
+     */
+
+    return &co->base;
+}
+
+void qemu_coroutine_delete(Coroutine *co_)
+{
+    CoroutineUContext *co = DO_UPCAST(CoroutineUContext, base, co_);
+
+    g_free(co->stack);
+    g_free(co);
+}
+
+CoroutineAction qemu_coroutine_switch(Coroutine *from_, Coroutine *to_,
+                                      CoroutineAction action)
+{
+    CoroutineUContext *from = DO_UPCAST(CoroutineUContext, base, from_);
+    CoroutineUContext *to = DO_UPCAST(CoroutineUContext, base, to_);
+    CoroutineThreadState *s = coroutine_get_thread_state();
+    int ret;
+
+    s->current = to_;
+
+    ret = sigsetjmp(from->env, 0);
+    if (ret == 0) {
+        siglongjmp(to->env, action);
+    }
+    return ret;
+}
+
+Coroutine *qemu_coroutine_self(void)
+{
+    CoroutineThreadState *s = coroutine_get_thread_state();
+
+    return s->current;
+}
+
+bool qemu_in_coroutine(void)
+{
+    CoroutineThreadState *s = pthread_getspecific(thread_state_key);
+
+    return s && s->current->caller;
+}
+
diff --git a/util/coroutine-ucontext.c b/util/coroutine-ucontext.c
new file mode 100644
index 0000000000..26cbebb7a7
--- /dev/null
+++ b/util/coroutine-ucontext.c
@@ -0,0 +1,194 @@
+/*
+ * ucontext coroutine initialization code
+ *
+ * Copyright (C) 2006  Anthony Liguori <anthony@codemonkey.ws>
+ * Copyright (C) 2011  Kevin Wolf <kwolf@redhat.com>
+ *
+ * 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, see <http://www.gnu.org/licenses/>.
+ */
+
+/* XXX Is there a nicer way to disable glibc's stack check for longjmp? */
+#ifdef _FORTIFY_SOURCE
+#undef _FORTIFY_SOURCE
+#endif
+#include <stdlib.h>
+#include <setjmp.h>
+#include <stdint.h>
+#include <ucontext.h>
+#include "qemu-common.h"
+#include "qemu/coroutine_int.h"
+
+#ifdef CONFIG_VALGRIND_H
+#include <valgrind/valgrind.h>
+#endif
+
+typedef struct {
+    Coroutine base;
+    void *stack;
+    sigjmp_buf env;
+
+#ifdef CONFIG_VALGRIND_H
+    unsigned int valgrind_stack_id;
+#endif
+
+} CoroutineUContext;
+
+/**
+ * Per-thread coroutine bookkeeping
+ */
+static __thread CoroutineUContext leader;
+static __thread Coroutine *current;
+
+/*
+ * 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 coroutine_trampoline(int i0, int i1)
+{
+    union cc_arg arg;
+    CoroutineUContext *self;
+    Coroutine *co;
+
+    arg.i[0] = i0;
+    arg.i[1] = i1;
+    self = arg.p;
+    co = &self->base;
+
+    /* Initialize longjmp environment and switch back the caller */
+    if (!sigsetjmp(self->env, 0)) {
+        siglongjmp(*(sigjmp_buf *)co->entry_arg, 1);
+    }
+
+    while (true) {
+        co->entry(co->entry_arg);
+        qemu_coroutine_switch(co, co->caller, COROUTINE_TERMINATE);
+    }
+}
+
+Coroutine *qemu_coroutine_new(void)
+{
+    const size_t stack_size = 1 << 20;
+    CoroutineUContext *co;
+    ucontext_t old_uc, uc;
+    sigjmp_buf old_env;
+    union cc_arg arg = {0};
+
+    /* The ucontext functions preserve signal masks which incurs a
+     * system call overhead.  sigsetjmp(buf, 0)/siglongjmp() does not
+     * preserve signal masks but only works on the current stack.
+     * Since we need a way to create and switch to a new stack, use
+     * the ucontext functions for that but sigsetjmp()/siglongjmp() for
+     * everything else.
+     */
+
+    if (getcontext(&uc) == -1) {
+        abort();
+    }
+
+    co = g_malloc0(sizeof(*co));
+    co->stack = g_malloc(stack_size);
+    co->base.entry_arg = &old_env; /* stash away our jmp_buf */
+
+    uc.uc_link = &old_uc;
+    uc.uc_stack.ss_sp = co->stack;
+    uc.uc_stack.ss_size = stack_size;
+    uc.uc_stack.ss_flags = 0;
+
+#ifdef CONFIG_VALGRIND_H
+    co->valgrind_stack_id =
+        VALGRIND_STACK_REGISTER(co->stack, co->stack + stack_size);
+#endif
+
+    arg.p = co;
+
+    makecontext(&uc, (void (*)(void))coroutine_trampoline,
+                2, arg.i[0], arg.i[1]);
+
+    /* swapcontext() in, siglongjmp() back out */
+    if (!sigsetjmp(old_env, 0)) {
+        swapcontext(&old_uc, &uc);
+    }
+    return &co->base;
+}
+
+#ifdef CONFIG_VALGRIND_H
+#ifdef CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE
+/* Work around an unused variable in the valgrind.h macro... */
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wunused-but-set-variable"
+#endif
+static inline void valgrind_stack_deregister(CoroutineUContext *co)
+{
+    VALGRIND_STACK_DEREGISTER(co->valgrind_stack_id);
+}
+#ifdef CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE
+#pragma GCC diagnostic pop
+#endif
+#endif
+
+void qemu_coroutine_delete(Coroutine *co_)
+{
+    CoroutineUContext *co = DO_UPCAST(CoroutineUContext, base, co_);
+
+#ifdef CONFIG_VALGRIND_H
+    valgrind_stack_deregister(co);
+#endif
+
+    g_free(co->stack);
+    g_free(co);
+}
+
+/* This function is marked noinline to prevent GCC from inlining it
+ * into coroutine_trampoline(). If we allow it to do that then it
+ * hoists the code to get the address of the TLS variable "current"
+ * out of the while() loop. This is an invalid transformation because
+ * the sigsetjmp() call may be called when running thread A but
+ * return in thread B, and so we might be in a different thread
+ * context each time round the loop.
+ */
+CoroutineAction __attribute__((noinline))
+qemu_coroutine_switch(Coroutine *from_, Coroutine *to_,
+                      CoroutineAction action)
+{
+    CoroutineUContext *from = DO_UPCAST(CoroutineUContext, base, from_);
+    CoroutineUContext *to = DO_UPCAST(CoroutineUContext, base, to_);
+    int ret;
+
+    current = to_;
+
+    ret = sigsetjmp(from->env, 0);
+    if (ret == 0) {
+        siglongjmp(to->env, action);
+    }
+    return ret;
+}
+
+Coroutine *qemu_coroutine_self(void)
+{
+    if (!current) {
+        current = &leader.base;
+    }
+    return current;
+}
+
+bool qemu_in_coroutine(void)
+{
+    return current && current->caller;
+}
diff --git a/util/coroutine-win32.c b/util/coroutine-win32.c
new file mode 100644
index 0000000000..4f922c53af
--- /dev/null
+++ b/util/coroutine-win32.c
@@ -0,0 +1,101 @@
+/*
+ * Win32 coroutine initialization code
+ *
+ * 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.
+ */
+
+#include "qemu-common.h"
+#include "qemu/coroutine_int.h"
+
+typedef struct
+{
+    Coroutine base;
+
+    LPVOID fiber;
+    CoroutineAction action;
+} CoroutineWin32;
+
+static __thread CoroutineWin32 leader;
+static __thread Coroutine *current;
+
+/* This function is marked noinline to prevent GCC from inlining it
+ * into coroutine_trampoline(). If we allow it to do that then it
+ * hoists the code to get the address of the TLS variable "current"
+ * out of the while() loop. This is an invalid transformation because
+ * the SwitchToFiber() call may be called when running thread A but
+ * return in thread B, and so we might be in a different thread
+ * context each time round the loop.
+ */
+CoroutineAction __attribute__((noinline))
+qemu_coroutine_switch(Coroutine *from_, Coroutine *to_,
+                      CoroutineAction action)
+{
+    CoroutineWin32 *from = DO_UPCAST(CoroutineWin32, base, from_);
+    CoroutineWin32 *to = DO_UPCAST(CoroutineWin32, base, to_);
+
+    current = to_;
+
+    to->action = action;
+    SwitchToFiber(to->fiber);
+    return from->action;
+}
+
+static void CALLBACK coroutine_trampoline(void *co_)
+{
+    Coroutine *co = co_;
+
+    while (true) {
+        co->entry(co->entry_arg);
+        qemu_coroutine_switch(co, co->caller, COROUTINE_TERMINATE);
+    }
+}
+
+Coroutine *qemu_coroutine_new(void)
+{
+    const size_t stack_size = 1 << 20;
+    CoroutineWin32 *co;
+
+    co = g_malloc0(sizeof(*co));
+    co->fiber = CreateFiber(stack_size, coroutine_trampoline, &co->base);
+    return &co->base;
+}
+
+void qemu_coroutine_delete(Coroutine *co_)
+{
+    CoroutineWin32 *co = DO_UPCAST(CoroutineWin32, base, co_);
+
+    DeleteFiber(co->fiber);
+    g_free(co);
+}
+
+Coroutine *qemu_coroutine_self(void)
+{
+    if (!current) {
+        current = &leader.base;
+        leader.fiber = ConvertThreadToFiber(NULL);
+    }
+    return current;
+}
+
+bool qemu_in_coroutine(void)
+{
+    return current && current->caller;
+}
diff --git a/util/qemu-coroutine-io.c b/util/qemu-coroutine-io.c
new file mode 100644
index 0000000000..e1eae7331e
--- /dev/null
+++ b/util/qemu-coroutine-io.c
@@ -0,0 +1,91 @@
+/*
+ * Coroutine-aware I/O functions
+ *
+ * Copyright (C) 2009-2010 Nippon Telegraph and Telephone Corporation.
+ * Copyright (c) 2011, Red Hat, Inc.
+ *
+ * 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-common.h"
+#include "qemu/sockets.h"
+#include "qemu/coroutine.h"
+#include "qemu/iov.h"
+#include "qemu/main-loop.h"
+
+ssize_t coroutine_fn
+qemu_co_sendv_recvv(int sockfd, struct iovec *iov, unsigned iov_cnt,
+                    size_t offset, size_t bytes, bool do_send)
+{
+    size_t done = 0;
+    ssize_t ret;
+    int err;
+    while (done < bytes) {
+        ret = iov_send_recv(sockfd, iov, iov_cnt,
+                            offset + done, bytes - done, do_send);
+        if (ret > 0) {
+            done += ret;
+        } else if (ret < 0) {
+            err = socket_error();
+            if (err == EAGAIN || err == EWOULDBLOCK) {
+                qemu_coroutine_yield();
+            } else if (done == 0) {
+                return -err;
+            } else {
+                break;
+            }
+        } else if (ret == 0 && !do_send) {
+            /* write (send) should never return 0.
+             * read (recv) returns 0 for end-of-file (-data).
+             * In both cases there's little point retrying,
+             * but we do for write anyway, just in case */
+            break;
+        }
+    }
+    return done;
+}
+
+ssize_t coroutine_fn
+qemu_co_send_recv(int sockfd, void *buf, size_t bytes, bool do_send)
+{
+    struct iovec iov = { .iov_base = buf, .iov_len = bytes };
+    return qemu_co_sendv_recvv(sockfd, &iov, 1, 0, bytes, do_send);
+}
+
+typedef struct {
+    Coroutine *co;
+    int fd;
+} FDYieldUntilData;
+
+static void fd_coroutine_enter(void *opaque)
+{
+    FDYieldUntilData *data = opaque;
+    qemu_set_fd_handler(data->fd, NULL, NULL, NULL);
+    qemu_coroutine_enter(data->co, NULL);
+}
+
+void coroutine_fn yield_until_fd_readable(int fd)
+{
+    FDYieldUntilData data;
+
+    assert(qemu_in_coroutine());
+    data.co = qemu_coroutine_self();
+    data.fd = fd;
+    qemu_set_fd_handler(fd, fd_coroutine_enter, NULL, &data);
+    qemu_coroutine_yield();
+}
diff --git a/util/qemu-coroutine-lock.c b/util/qemu-coroutine-lock.c
new file mode 100644
index 0000000000..130ee19d17
--- /dev/null
+++ b/util/qemu-coroutine-lock.c
@@ -0,0 +1,186 @@
+/*
+ * coroutine queues and locks
+ *
+ * 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.
+ */
+
+#include "qemu-common.h"
+#include "qemu/coroutine.h"
+#include "qemu/coroutine_int.h"
+#include "qemu/queue.h"
+#include "trace.h"
+
+void qemu_co_queue_init(CoQueue *queue)
+{
+    QTAILQ_INIT(&queue->entries);
+}
+
+void coroutine_fn qemu_co_queue_wait(CoQueue *queue)
+{
+    Coroutine *self = qemu_coroutine_self();
+    QTAILQ_INSERT_TAIL(&queue->entries, self, co_queue_next);
+    qemu_coroutine_yield();
+    assert(qemu_in_coroutine());
+}
+
+/**
+ * qemu_co_queue_run_restart:
+ *
+ * Enter each coroutine that was previously marked for restart by
+ * qemu_co_queue_next() or qemu_co_queue_restart_all().  This function is
+ * invoked by the core coroutine code when the current coroutine yields or
+ * terminates.
+ */
+void qemu_co_queue_run_restart(Coroutine *co)
+{
+    Coroutine *next;
+
+    trace_qemu_co_queue_run_restart(co);
+    while ((next = QTAILQ_FIRST(&co->co_queue_wakeup))) {
+        QTAILQ_REMOVE(&co->co_queue_wakeup, next, co_queue_next);
+        qemu_coroutine_enter(next, NULL);
+    }
+}
+
+static bool qemu_co_queue_do_restart(CoQueue *queue, bool single)
+{
+    Coroutine *self = qemu_coroutine_self();
+    Coroutine *next;
+
+    if (QTAILQ_EMPTY(&queue->entries)) {
+        return false;
+    }
+
+    while ((next = QTAILQ_FIRST(&queue->entries)) != NULL) {
+        QTAILQ_REMOVE(&queue->entries, next, co_queue_next);
+        QTAILQ_INSERT_TAIL(&self->co_queue_wakeup, next, co_queue_next);
+        trace_qemu_co_queue_next(next);
+        if (single) {
+            break;
+        }
+    }
+    return true;
+}
+
+bool coroutine_fn qemu_co_queue_next(CoQueue *queue)
+{
+    assert(qemu_in_coroutine());
+    return qemu_co_queue_do_restart(queue, true);
+}
+
+void coroutine_fn qemu_co_queue_restart_all(CoQueue *queue)
+{
+    assert(qemu_in_coroutine());
+    qemu_co_queue_do_restart(queue, false);
+}
+
+bool qemu_co_enter_next(CoQueue *queue)
+{
+    Coroutine *next;
+
+    next = QTAILQ_FIRST(&queue->entries);
+    if (!next) {
+        return false;
+    }
+
+    QTAILQ_REMOVE(&queue->entries, next, co_queue_next);
+    qemu_coroutine_enter(next, NULL);
+    return true;
+}
+
+bool qemu_co_queue_empty(CoQueue *queue)
+{
+    return QTAILQ_FIRST(&queue->entries) == NULL;
+}
+
+void qemu_co_mutex_init(CoMutex *mutex)
+{
+    memset(mutex, 0, sizeof(*mutex));
+    qemu_co_queue_init(&mutex->queue);
+}
+
+void coroutine_fn qemu_co_mutex_lock(CoMutex *mutex)
+{
+    Coroutine *self = qemu_coroutine_self();
+
+    trace_qemu_co_mutex_lock_entry(mutex, self);
+
+    while (mutex->locked) {
+        qemu_co_queue_wait(&mutex->queue);
+    }
+
+    mutex->locked = true;
+
+    trace_qemu_co_mutex_lock_return(mutex, self);
+}
+
+void coroutine_fn qemu_co_mutex_unlock(CoMutex *mutex)
+{
+    Coroutine *self = qemu_coroutine_self();
+
+    trace_qemu_co_mutex_unlock_entry(mutex, self);
+
+    assert(mutex->locked == true);
+    assert(qemu_in_coroutine());
+
+    mutex->locked = false;
+    qemu_co_queue_next(&mutex->queue);
+
+    trace_qemu_co_mutex_unlock_return(mutex, self);
+}
+
+void qemu_co_rwlock_init(CoRwlock *lock)
+{
+    memset(lock, 0, sizeof(*lock));
+    qemu_co_queue_init(&lock->queue);
+}
+
+void qemu_co_rwlock_rdlock(CoRwlock *lock)
+{
+    while (lock->writer) {
+        qemu_co_queue_wait(&lock->queue);
+    }
+    lock->reader++;
+}
+
+void qemu_co_rwlock_unlock(CoRwlock *lock)
+{
+    assert(qemu_in_coroutine());
+    if (lock->writer) {
+        lock->writer = false;
+        qemu_co_queue_restart_all(&lock->queue);
+    } else {
+        lock->reader--;
+        assert(lock->reader >= 0);
+        /* Wakeup only one waiting writer */
+        if (!lock->reader) {
+            qemu_co_queue_next(&lock->queue);
+        }
+    }
+}
+
+void qemu_co_rwlock_wrlock(CoRwlock *lock)
+{
+    while (lock->writer || lock->reader) {
+        qemu_co_queue_wait(&lock->queue);
+    }
+    lock->writer = true;
+}
diff --git a/util/qemu-coroutine-sleep.c b/util/qemu-coroutine-sleep.c
new file mode 100644
index 0000000000..b35db56356
--- /dev/null
+++ b/util/qemu-coroutine-sleep.c
@@ -0,0 +1,41 @@
+/*
+ * QEMU coroutine sleep
+ *
+ * Copyright IBM, Corp. 2011
+ *
+ * Authors:
+ *  Stefan Hajnoczi    <stefanha@linux.vnet.ibm.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 "qemu/coroutine.h"
+#include "qemu/timer.h"
+#include "block/aio.h"
+
+typedef struct CoSleepCB {
+    QEMUTimer *ts;
+    Coroutine *co;
+} CoSleepCB;
+
+static void co_sleep_cb(void *opaque)
+{
+    CoSleepCB *sleep_cb = opaque;
+
+    qemu_coroutine_enter(sleep_cb->co, NULL);
+}
+
+void coroutine_fn co_aio_sleep_ns(AioContext *ctx, QEMUClockType type,
+                                  int64_t ns)
+{
+    CoSleepCB sleep_cb = {
+        .co = qemu_coroutine_self(),
+    };
+    sleep_cb.ts = aio_timer_new(ctx, type, SCALE_NS, co_sleep_cb, &sleep_cb);
+    timer_mod(sleep_cb.ts, qemu_clock_get_ns(type) + ns);
+    qemu_coroutine_yield();
+    timer_del(sleep_cb.ts);
+    timer_free(sleep_cb.ts);
+}
diff --git a/util/qemu-coroutine.c b/util/qemu-coroutine.c
new file mode 100644
index 0000000000..8953560223
--- /dev/null
+++ b/util/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 "qemu/coroutine.h"
+#include "qemu/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);
+}