main-loop: create main-loop.h

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

12 files changed, 336 insertions, 64 deletions

diff --git a/async.c b/async.c
index ca13962222..332d511ed5 100644
--- a/async.c
+++ b/async.c
@@ -24,6 +24,7 @@
 
 #include "qemu-common.h"
 #include "qemu-aio.h"
+#include "main-loop.h"
 
 /* Anchor of the list of Bottom Halves belonging to the context */
 static struct QEMUBH *first_bh;
diff --git a/cpus.c b/cpus.c
index 1328baac70..64237b4255 100644
--- a/cpus.c
+++ b/cpus.c
@@ -33,17 +33,12 @@
 
 #include "qemu-thread.h"
 #include "cpus.h"
+#include "main-loop.h"
 
 #ifndef _WIN32
 #include "compatfd.h"
 #endif
 
-#ifdef SIGRTMIN
-#define SIG_IPI (SIGRTMIN+4)
-#else
-#define SIG_IPI SIGUSR1
-#endif
-
 #ifdef CONFIG_LINUX
 
 #include <sys/prctl.h>
diff --git a/cpus.h b/cpus.h
index 58858855ff..4ccf986d3f 100644
--- a/cpus.h
+++ b/cpus.h
@@ -2,7 +2,6 @@
 #define QEMU_CPUS_H
 
 /* cpus.c */
-int qemu_init_main_loop(void);
 void qemu_main_loop_start(void);
 void resume_all_vcpus(void);
 void pause_all_vcpus(void);
diff --git a/iohandler.c b/iohandler.c
index 4cc1c5ade6..687dc565a4 100644
--- a/iohandler.c
+++ b/iohandler.c
@@ -26,6 +26,7 @@
 #include "qemu-common.h"
 #include "qemu-char.h"
 #include "qemu-queue.h"
+#include "main-loop.h"
 
 #ifndef _WIN32
 #include <sys/wait.h>
diff --git a/main-loop.h b/main-loop.h
new file mode 100644
index 0000000000..a73b9c0bbe
--- /dev/null
+++ b/main-loop.h
@@ -0,0 +1,327 @@
+/*
+ * QEMU System Emulator
+ *
+ * Copyright (c) 2003-2008 Fabrice Bellard
+ *
+ * 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_MAIN_LOOP_H
+#define QEMU_MAIN_LOOP_H 1
+
+#ifdef SIGRTMIN
+#define SIG_IPI (SIGRTMIN+4)
+#else
+#define SIG_IPI SIGUSR1
+#endif
+
+/**
+ * qemu_init_main_loop: Set up the process so that it can run the main loop.
+ *
+ * This includes setting up signal handlers.  It should be called before
+ * any other threads are created.  In addition, threads other than the
+ * main one should block signals that are trapped by the main loop.
+ * For simplicity, you can consider these signals to be safe: SIGUSR1,
+ * SIGUSR2, thread signals (SIGFPE, SIGILL, SIGSEGV, SIGBUS) and real-time
+ * signals if available.  Remember that Windows in practice does not have
+ * signals, though.
+ */
+int qemu_init_main_loop(void);
+
+/**
+ * main_loop_wait: Run one iteration of the main loop.
+ *
+ * If @nonblocking is true, poll for events, otherwise suspend until
+ * one actually occurs.  The main loop usually consists of a loop that
+ * repeatedly calls main_loop_wait(false).
+ *
+ * Main loop services include file descriptor callbacks, bottom halves
+ * and timers (defined in qemu-timer.h).  Bottom halves are similar to timers
+ * that execute immediately, but have a lower overhead and scheduling them
+ * is wait-free, thread-safe and signal-safe.
+ *
+ * It is sometimes useful to put a whole program in a coroutine.  In this
+ * case, the coroutine actually should be started from within the main loop,
+ * so that the main loop can run whenever the coroutine yields.  To do this,
+ * you can use a bottom half to enter the coroutine as soon as the main loop
+ * starts:
+ *
+ *     void enter_co_bh(void *opaque) {
+ *         QEMUCoroutine *co = opaque;
+ *         qemu_coroutine_enter(co, NULL);
+ *     }
+ *
+ *     ...
+ *     QEMUCoroutine *co = qemu_coroutine_create(coroutine_entry);
+ *     QEMUBH *start_bh = qemu_bh_new(enter_co_bh, co);
+ *     qemu_bh_schedule(start_bh);
+ *     while (...) {
+ *         main_loop_wait(false);
+ *     }
+ *
+ * (In the future we may provide a wrapper for this).
+ *
+ * @nonblocking: Whether the caller should block until an event occurs.
+ */
+int main_loop_wait(int nonblocking);
+
+/**
+ * qemu_notify_event: Force processing of pending events.
+ *
+ * Similar to signaling a condition variable, qemu_notify_event forces
+ * main_loop_wait to look at pending events and exit.  The caller of
+ * main_loop_wait will usually call it again very soon, so qemu_notify_event
+ * also has the side effect of recalculating the sets of file descriptors
+ * that the main loop waits for.
+ *
+ * Calling qemu_notify_event is rarely necessary, because main loop
+ * services (bottom halves and timers) call it themselves.  One notable
+ * exception occurs when using qemu_set_fd_handler2 (see below).
+ */
+void qemu_notify_event(void);
+
+#ifdef _WIN32
+/* return TRUE if no sleep should be done afterwards */
+typedef int PollingFunc(void *opaque);
+
+/**
+ * qemu_add_polling_cb: Register a Windows-specific polling callback
+ *
+ * Currently, under Windows some events are polled rather than waited for.
+ * Polling callbacks do not ensure that @func is called timely, because
+ * the main loop might wait for an arbitrarily long time.  If possible,
+ * you should instead create a separate thread that does a blocking poll
+ * and set a Win32 event object.  The event can then be passed to
+ * qemu_add_wait_object.
+ *
+ * Polling callbacks really have nothing Windows specific in them, but
+ * as they are a hack and are currenly not necessary under POSIX systems,
+ * they are only available when QEMU is running under Windows.
+ *
+ * @func: The function that does the polling, and returns 1 to force
+ * immediate completion of main_loop_wait.
+ * @opaque: A pointer-size value that is passed to @func.
+ */
+int qemu_add_polling_cb(PollingFunc *func, void *opaque);
+
+/**
+ * qemu_del_polling_cb: Unregister a Windows-specific polling callback
+ *
+ * This function removes a callback that was registered with
+ * qemu_add_polling_cb.
+ *
+ * @func: The function that was passed to qemu_add_polling_cb.
+ * @opaque: A pointer-size value that was passed to qemu_add_polling_cb.
+ */
+void qemu_del_polling_cb(PollingFunc *func, void *opaque);
+
+/* Wait objects handling */
+typedef void WaitObjectFunc(void *opaque);
+
+/**
+ * qemu_add_wait_object: Register a callback for a Windows handle
+ *
+ * Under Windows, the iohandler mechanism can only be used with sockets.
+ * QEMU must use the WaitForMultipleObjects API to wait on other handles.
+ * This function registers a #HANDLE with QEMU, so that it will be included
+ * in the main loop's calls to WaitForMultipleObjects.  When the handle
+ * is in a signaled state, QEMU will call @func.
+ *
+ * @handle: The Windows handle to be observed.
+ * @func: A function to be called when @handle is in a signaled state.
+ * @opaque: A pointer-size value that is passed to @func.
+ */
+int qemu_add_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque);
+
+/**
+ * qemu_del_wait_object: Unregister a callback for a Windows handle
+ *
+ * This function removes a callback that was registered with
+ * qemu_add_wait_object.
+ *
+ * @func: The function that was passed to qemu_add_wait_object.
+ * @opaque: A pointer-size value that was passed to qemu_add_wait_object.
+ */
+void qemu_del_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque);
+#endif
+
+/* async I/O support */
+
+typedef void IOReadHandler(void *opaque, const uint8_t *buf, int size);
+typedef int IOCanReadHandler(void *opaque);
+typedef void IOHandler(void *opaque);
+
+/**
+ * qemu_set_fd_handler2: Register a file descriptor with the main loop
+ *
+ * This function tells the main loop to wake up whenever one of the
+ * following conditions is true:
+ *
+ * 1) if @fd_write is not %NULL, when the file descriptor is writable;
+ *
+ * 2) if @fd_read is not %NULL, when the file descriptor is readable.
+ *
+ * @fd_read_poll can be used to disable the @fd_read callback temporarily.
+ * This is useful to avoid calling qemu_set_fd_handler2 every time the
+ * client becomes interested in reading (or dually, stops being interested).
+ * A typical example is when @fd is a listening socket and you want to bound
+ * the number of active clients.  Remember to call qemu_notify_event whenever
+ * the condition may change from %false to %true.
+ *
+ * The callbacks that are set up by qemu_set_fd_handler2 are level-triggered.
+ * If @fd_read does not read from @fd, or @fd_write does not write to @fd
+ * until its buffers are full, they will be called again on the next
+ * iteration.
+ *
+ * @fd: The file descriptor to be observed.  Under Windows it must be
+ * a #SOCKET.
+ *
+ * @fd_read_poll: A function that returns 1 if the @fd_read callback
+ * should be fired.  If the function returns 0, the main loop will not
+ * end its iteration even if @fd becomes readable.
+ *
+ * @fd_read: A level-triggered callback that is fired if @fd is readable
+ * at the beginning of a main loop iteration, or if it becomes readable
+ * during one.
+ *
+ * @fd_write: A level-triggered callback that is fired when @fd is writable
+ * at the beginning of a main loop iteration, or if it becomes writable
+ * during one.
+ *
+ * @opaque: A pointer-sized value that is passed to @fd_read_poll,
+ * @fd_read and @fd_write.
+ */
+int qemu_set_fd_handler2(int fd,
+                         IOCanReadHandler *fd_read_poll,
+                         IOHandler *fd_read,
+                         IOHandler *fd_write,
+                         void *opaque);
+
+/**
+ * qemu_set_fd_handler: Register a file descriptor with the main loop
+ *
+ * This function tells the main loop to wake up whenever one of the
+ * following conditions is true:
+ *
+ * 1) if @fd_write is not %NULL, when the file descriptor is writable;
+ *
+ * 2) if @fd_read is not %NULL, when the file descriptor is readable.
+ *
+ * The callbacks that are set up by qemu_set_fd_handler are level-triggered.
+ * If @fd_read does not read from @fd, or @fd_write does not write to @fd
+ * until its buffers are full, they will be called again on the next
+ * iteration.
+ *
+ * @fd: The file descriptor to be observed.  Under Windows it must be
+ * a #SOCKET.
+ *
+ * @fd_read: A level-triggered callback that is fired if @fd is readable
+ * at the beginning of a main loop iteration, or if it becomes readable
+ * during one.
+ *
+ * @fd_write: A level-triggered callback that is fired when @fd is writable
+ * at the beginning of a main loop iteration, or if it becomes writable
+ * during one.
+ *
+ * @opaque: A pointer-sized value that is passed to @fd_read and @fd_write.
+ */
+int qemu_set_fd_handler(int fd,
+                        IOHandler *fd_read,
+                        IOHandler *fd_write,
+                        void *opaque);
+
+typedef struct QEMUBH QEMUBH;
+typedef void QEMUBHFunc(void *opaque);
+
+/**
+ * qemu_bh_new: Allocate a new bottom half structure.
+ *
+ * Bottom halves are lightweight callbacks whose invocation is guaranteed
+ * to be wait-free, thread-safe and signal-safe.  The #QEMUBH structure
+ * is opaque and must be allocated prior to its use.
+ */
+QEMUBH *qemu_bh_new(QEMUBHFunc *cb, void *opaque);
+
+/**
+ * qemu_bh_schedule: Schedule a bottom half.
+ *
+ * Scheduling a bottom half interrupts the main loop and causes the
+ * execution of the callback that was passed to qemu_bh_new.
+ *
+ * Bottom halves that are scheduled from a bottom half handler are instantly
+ * invoked.  This can create an infinite loop if a bottom half handler
+ * schedules itself.
+ *
+ * @bh: The bottom half to be scheduled.
+ */
+void qemu_bh_schedule(QEMUBH *bh);
+
+/**
+ * qemu_bh_cancel: Cancel execution of a bottom half.
+ *
+ * Canceling execution of a bottom half undoes the effect of calls to
+ * qemu_bh_schedule without freeing its resources yet.  While cancellation
+ * itself is also wait-free and thread-safe, it can of course race with the
+ * loop that executes bottom halves unless you are holding the iothread
+ * mutex.  This makes it mostly useless if you are not holding the mutex.
+ *
+ * @bh: The bottom half to be canceled.
+ */
+void qemu_bh_cancel(QEMUBH *bh);
+
+/**
+ *qemu_bh_delete: Cancel execution of a bottom half and free its resources.
+ *
+ * Deleting a bottom half frees the memory that was allocated for it by
+ * qemu_bh_new.  It also implies canceling the bottom half if it was
+ * scheduled.
+ *
+ * @bh: The bottom half to be deleted.
+ */
+void qemu_bh_delete(QEMUBH *bh);
+
+#ifdef CONFIG_POSIX
+/**
+ * qemu_add_child_watch: Register a child process for reaping.
+ *
+ * Under POSIX systems, a parent process must read the exit status of
+ * its child processes using waitpid, or the operating system will not
+ * free some of the resources attached to that process.
+ *
+ * This function directs the QEMU main loop to observe a child process
+ * and call waitpid as soon as it exits; the watch is then removed
+ * automatically.  It is useful whenever QEMU forks a child process
+ * but will find out about its termination by other means such as a
+ * "broken pipe".
+ *
+ * @pid: The pid that QEMU should observe.
+ */
+int qemu_add_child_watch(pid_t pid);
+#endif
+
+/* internal interfaces */
+
+void qemu_iohandler_fill(int *pnfds, fd_set *readfds, fd_set *writefds, fd_set *xfds);
+void qemu_iohandler_poll(fd_set *readfds, fd_set *writefds, fd_set *xfds, int rc);
+
+void qemu_bh_schedule_idle(QEMUBH *bh);
+int qemu_bh_poll(void);
+void qemu_bh_update_timeout(int *timeout);
+
+#endif
diff --git a/qemu-char.h b/qemu-char.h
index eebbdd8f01..7efcf99f53 100644
--- a/qemu-char.h
+++ b/qemu-char.h
@@ -7,6 +7,7 @@
 #include "qemu-config.h"
 #include "qobject.h"
 #include "qstring.h"
+#include "main-loop.h"
 
 /* character device */
 
@@ -237,15 +238,4 @@ void qemu_chr_close_mem(CharDriverState *chr);
 QString *qemu_chr_mem_to_qs(CharDriverState *chr);
 size_t qemu_chr_mem_osize(const CharDriverState *chr);
 
-/* async I/O support */
-
-int qemu_set_fd_handler2(int fd,
-                         IOCanReadHandler *fd_read_poll,
-                         IOHandler *fd_read,
-                         IOHandler *fd_write,
-                         void *opaque);
-int qemu_set_fd_handler(int fd,
-                        IOHandler *fd_read,
-                        IOHandler *fd_write,
-                        void *opaque);
 #endif
diff --git a/qemu-common.h b/qemu-common.h
index fffdefdeca..5997f58540 100644
--- a/qemu-common.h
+++ b/qemu-common.h
@@ -13,7 +13,6 @@
 
 typedef struct QEMUTimer QEMUTimer;
 typedef struct QEMUFile QEMUFile;
-typedef struct QEMUBH QEMUBH;
 typedef struct DeviceState DeviceState;
 
 struct Monitor;
@@ -117,23 +116,6 @@ extern int use_icount;
 int qemu_main(int argc, char **argv, char **envp);
 #endif
 
-/* bottom halves */
-typedef void QEMUBHFunc(void *opaque);
-
-QEMUBH *qemu_bh_new(QEMUBHFunc *cb, void *opaque);
-void qemu_bh_schedule(QEMUBH *bh);
-/* Bottom halfs that are scheduled from a bottom half handler are instantly
- * invoked.  This can create an infinite loop if a bottom half handler
- * schedules itself.  qemu_bh_schedule_idle() avoids this infinite loop by
- * ensuring that the bottom half isn't executed until the next main loop
- * iteration.
- */
-void qemu_bh_schedule_idle(QEMUBH *bh);
-void qemu_bh_cancel(QEMUBH *bh);
-void qemu_bh_delete(QEMUBH *bh);
-int qemu_bh_poll(void);
-void qemu_bh_update_timeout(int *timeout);
-
 void qemu_get_timedate(struct tm *tm, int offset);
 int qemu_timedate_diff(struct tm *tm);
 
@@ -196,7 +178,6 @@ ssize_t qemu_write_full(int fd, const void *buf, size_t count)
 void qemu_set_cloexec(int fd);
 
 #ifndef _WIN32
-int qemu_add_child_watch(pid_t pid);
 int qemu_eventfd(int pipefd[2]);
 int qemu_pipe(int pipefd[2]);
 #endif
@@ -211,14 +192,6 @@ int qemu_pipe(int pipefd[2]);
 
 void QEMU_NORETURN hw_error(const char *fmt, ...) GCC_FMT_ATTR(1, 2);
 
-/* IO callbacks.  */
-typedef void IOReadHandler(void *opaque, const uint8_t *buf, int size);
-typedef int IOCanReadHandler(void *opaque);
-typedef void IOHandler(void *opaque);
-
-void qemu_iohandler_fill(int *pnfds, fd_set *readfds, fd_set *writefds, fd_set *xfds);
-void qemu_iohandler_poll(fd_set *readfds, fd_set *writefds, fd_set *xfds, int rc);
-
 struct ParallelIOArg {
     void *buffer;
     int count;
@@ -280,9 +253,6 @@ void cpu_exec_init_all(void);
 void cpu_save(QEMUFile *f, void *opaque);
 int cpu_load(QEMUFile *f, void *opaque, int version_id);
 
-/* Force QEMU to process pending events */
-void qemu_notify_event(void);
-
 /* Unblock cpu */
 void qemu_cpu_kick(void *env);
 void qemu_cpu_kick_self(void);
diff --git a/qemu-coroutine-lock.c b/qemu-coroutine-lock.c
index 2a385a3bb8..6b58160058 100644
--- a/qemu-coroutine-lock.c
+++ b/qemu-coroutine-lock.c
@@ -26,6 +26,7 @@
 #include "qemu-coroutine.h"
 #include "qemu-coroutine-int.h"
 #include "qemu-queue.h"
+#include "main-loop.h"
 #include "trace.h"
 
 static QTAILQ_HEAD(, Coroutine) unlock_bh_queue =
diff --git a/qemu-os-win32.h b/qemu-os-win32.h
index 8a069d7fb6..5a9fd5dade 100644
--- a/qemu-os-win32.h
+++ b/qemu-os-win32.h
@@ -28,24 +28,11 @@
 
 #include <windows.h>
 #include <winsock2.h>
+#include "main-loop.h"
 
 /* Declaration of ffs() is missing in MinGW's strings.h. */
 int ffs(int i);
 
-/* Polling handling */
-
-/* return TRUE if no sleep should be done afterwards */
-typedef int PollingFunc(void *opaque);
-
-int qemu_add_polling_cb(PollingFunc *func, void *opaque);
-void qemu_del_polling_cb(PollingFunc *func, void *opaque);
-
-/* Wait objects handling */
-typedef void WaitObjectFunc(void *opaque);
-
-int qemu_add_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque);
-void qemu_del_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque);
-
 void os_host_main_loop_wait(int *timeout);
 
 static inline void os_setup_signal_handling(void) {}
diff --git a/qemu-timer.h b/qemu-timer.h
index 9f4ffed75c..67ca72e045 100644
--- a/qemu-timer.h
+++ b/qemu-timer.h
@@ -2,6 +2,7 @@
 #define QEMU_TIMER_H
 
 #include "qemu-common.h"
+#include "main-loop.h"
 #include "notify.h"
 #include <time.h>
 #include <sys/time.h>
diff --git a/sysemu.h b/sysemu.h
index 7d288f865d..22cd720016 100644
--- a/sysemu.h
+++ b/sysemu.h
@@ -8,6 +8,7 @@
 #include "qemu-timer.h"
 #include "qapi-types.h"
 #include "notify.h"
+#include "main-loop.h"
 
 /* vl.c */
 
@@ -64,8 +65,6 @@ void do_info_snapshots(Monitor *mon);
 
 void qemu_announce_self(void);
 
-int main_loop_wait(int nonblocking);
-
 bool qemu_savevm_state_blocked(Monitor *mon);
 int qemu_savevm_state_begin(Monitor *mon, QEMUFile *f, int blk_enable,
                             int shared);
diff --git a/vl.c b/vl.c
index cf25d65058..ef0936a325 100644
--- a/vl.c
+++ b/vl.c
@@ -148,6 +148,7 @@ int main(int argc, char **argv)
 #include "qemu-objects.h"
 #include "qemu-options.h"
 #include "qmp-commands.h"
+#include "main-loop.h"
 #ifdef CONFIG_VIRTFS
 #include "fsdev/qemu-fsdev.h"
 #endif