[Qemu-devel] [PATCH v2 3/5] iohandlers: Allow each iohandler to be enabled/disabled individually

[Amit Shah <amit.shah@redhat.com>]

Each iohandler for an fd can now be individually enabled or disabled.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
---
 qemu-char.h |    4 +++
 vl.c        |   78 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 79 insertions(+), 3 deletions(-)

diff --git a/qemu-char.h b/qemu-char.h
index 0ef83f4..e88a108 100644
--- a/qemu-char.h
+++ b/qemu-char.h
@@ -115,6 +115,10 @@ int assign_fd_handlers(int fd,
                        IOHandler *fd_write,
                        void *opaque);
 void remove_fd_handlers(int fd);
+int set_read_poll_fd_action(int fd, bool enable);
+int set_read_fd_action(int fd, bool enable);
+int set_write_fd_action(int fd, bool enable);
+
 int qemu_set_fd_handler2(int fd,
                          IOCanReadHandler *fd_read_poll,
                          IOHandler *fd_read,
diff --git a/vl.c b/vl.c
index 30256e1..b9c902a 100644
--- a/vl.c
+++ b/vl.c
@@ -1014,6 +1014,9 @@ typedef struct IOHandlerRecord {
     IOHandler *fd_write;
     int deleted;
     void *opaque;
+    bool read_poll_enabled;
+    bool read_enabled;
+    bool write_enabled;
     /* temporary data */
     struct pollfd *ufd;
     QLIST_ENTRY(IOHandlerRecord) next;
@@ -1035,6 +1038,57 @@ static IOHandlerRecord *get_iohandler(int fd)
 }
 
 /*
+ * Enable the fd_read_poll handler for fd if the fd_read_poll handler exists.
+ */
+int set_read_poll_fd_action(int fd, bool enable)
+{
+    IOHandlerRecord *ioh;
+
+    ioh = get_iohandler(fd);
+
+    if (!ioh) {
+        return -1;
+    }
+    ioh->read_poll_enabled = enable;
+
+    return 0;
+}
+
+/*
+ * Enable the fd_read handler for fd if the fd_read handler exists.
+ */
+int set_read_fd_action(int fd, bool enable)
+{
+    IOHandlerRecord *ioh;
+
+    ioh = get_iohandler(fd);
+
+    if (!ioh) {
+        return -1;
+    }
+    ioh->read_enabled = enable;
+
+    return 0;
+}
+
+/*
+ * Enable the fd_write handler for fd if the fd_write handler exists.
+ */
+int set_write_fd_action(int fd, bool enable)
+{
+    IOHandlerRecord *ioh;
+
+    ioh = get_iohandler(fd);
+
+    if (!ioh) {
+        return -1;
+    }
+    ioh->write_enabled = enable;
+
+    return 0;
+}
+
+/*
  * Specify function pointers for the various IOHandlers for an fd here.
  *
  * XXX: fd_read_poll should be suppressed, but an API change is
@@ -1067,6 +1121,20 @@ int assign_fd_handlers(int fd,
     ioh->opaque = opaque;
     ioh->deleted = 0;
 
+    /*
+     * To maintain compatibility with the callers that expect all
+     * handlers to be enabled.  Callers that wish for some handlers
+     * not to be enabled right away should ensure they call
+     * set_xx_fd_action(fd, false) after this call.
+     *
+     * Note: if gets threading and one day is capable of running
+     * main_loop_wait() in parallel to this function, ensure this call
+     * and any later set_xx_fd_action() calls can execute atomically.
+     */
+    set_read_poll_fd_action(fd, true);
+    set_read_fd_action(fd, true);
+    set_write_fd_action(fd, true);
+
     return 0;
 }
 
@@ -1079,6 +1147,10 @@ void remove_fd_handlers(int fd)
     assign_fd_handlers(fd, NULL, NULL, NULL, NULL);
 }
 
+/*
+ * TODO: Deprecate these two function calls in favour of
+ * assign_fd_handlers().
+ */
 int qemu_set_fd_handler2(int fd,
                          IOCanReadHandler *fd_read_poll,
                          IOHandler *fd_read,
@@ -1349,14 +1421,14 @@ void main_loop_wait(int nonblocking)
     QLIST_FOREACH(ioh, &io_handlers, next) {
         if (ioh->deleted)
             continue;
-        if (ioh->fd_read &&
+        if (ioh->fd_read && ioh->read_enabled &&
             (!ioh->fd_read_poll ||
-             ioh->fd_read_poll(ioh->opaque) != 0)) {
+             (!ioh->read_poll_enabled || ioh->fd_read_poll(ioh->opaque) != 0))) {
             FD_SET(ioh->fd, &rfds);
             if (ioh->fd > nfds)
                 nfds = ioh->fd;
         }
-        if (ioh->fd_write) {
+        if (ioh->fd_write && ioh->write_enabled) {
             FD_SET(ioh->fd, &wfds);
             if (ioh->fd > nfds)
                 nfds = ioh->fd;
-- 
1.7.3.4