Only run one toplevel callback per event loop iteration.

This change attempts to reinstate as a universal property something
which was sporadically true of the ad-hockery that came before
toplevel callbacks: that if there's a _very long_ queue of things to
be done through the callback mechanism, the doing of them will be
interleaved with re-checks of other event sources, which might (e.g.)
cause a flag to be set which makes the next callback decide not to do
anything after all.

git-svn-id: http://svn.tartarus.org/sgt/putty@10040 cda61777-01e9-0310-a592-d414129be87e

diff --git a/callback.c b/callback.c
index e62fcd7d47245a9b431619d85b1be6e4517c56b2..c850f6bca31246ab590f24498a9d6445e53c8be0 100644 (file)
--- a/callback.c
+++ b/callback.c
@@ -26,10 +26,28 @@ void request_callback_notifications(toplevel_callback_notify_fn_t fn,
     frontend = fr;
 }
 
+void stoat_callback(void *ctx)
+{
+    static int stoat = 0;
+    if (++stoat % 1000 == 0)
+        debug(("stoat %d\n", stoat));
+    queue_toplevel_callback(stoat_callback, NULL);
+}
+void queue_stoat(void)
+{
+    static int stoat = 0;
+    if (!stoat) {
+        stoat = 1;
+        queue_toplevel_callback(stoat_callback, NULL);
+    }
+}
+
 void queue_toplevel_callback(toplevel_callback_fn_t fn, void *ctx)
 {
     struct callback *cb;
 
+    queue_stoat();
+
     cb = snew(struct callback);
     cb->fn = fn;
     cb->ctx = ctx;
@@ -50,19 +68,27 @@ void queue_toplevel_callback(toplevel_callback_fn_t fn, void *ctx)
 
 void run_toplevel_callbacks(void)
 {
-    while (cbhead) {
+    queue_stoat();
+    if (cbhead) {
         struct callback *cb = cbhead;
         /*
          * Careful ordering here. We call the function _before_
          * advancing cbhead (though, of course, we must free cb
          * _after_ advancing it). This means that if the very last
          * callback schedules another callback, cbhead does not become
-         * NULL at any point in this while loop, and so the frontend
-         * notification function won't be needlessly pestered.
+         * NULL at any point, and so the frontend notification
+         * function won't be needlessly pestered.
          */
         cb->fn(cb->ctx);
         cbhead = cb->next;
         sfree(cb);
+        if (!cbhead)
+            cbtail = NULL;
     }
-    cbtail = NULL;
+}
+
+int toplevel_callback_pending(void)
+{
+    queue_stoat();
+    return cbhead != NULL;
 }

diff --git a/putty.h b/putty.h
index 7fbb75ec57b98280b9fca1bfa05fa182db8aa0ee..89140f80afa50b8c7dc8797abd3a45ad36f1cdee 100644 (file)
--- a/putty.h
+++ b/putty.h
@@ -1403,11 +1403,16 @@ void timer_change_notify(unsigned long next);
  * top-level event loop. However, if a front end doesn't have control
  * over its own event loop (e.g. because it's using GTK) then it can
  * instead request notifications when a callback is available, so that
- * it knows to ask its delegate event loop to do the same thing.
+ * it knows to ask its delegate event loop to do the same thing. Also,
+ * if a front end needs to know whether a callback is pending without
+ * actually running it (e.g. so as to put a zero timeout on a select()
+ * call) then it can call toplevel_callback_pending(), which will
+ * return true if at least one callback is in the queue.
  */
 typedef void (*toplevel_callback_fn_t)(void *ctx);
 void queue_toplevel_callback(toplevel_callback_fn_t fn, void *ctx);
 void run_toplevel_callbacks(void);
+int toplevel_callback_pending(void);
 
 typedef void (*toplevel_callback_notify_fn_t)(void *frontend);
 void request_callback_notifications(toplevel_callback_notify_fn_t notify,

diff --git a/unix/gtkwin.c b/unix/gtkwin.c
index 29ac22844e6a40bbc24b9a88fb9c77d84703b081..88ce8b5505d4dfb5349c984447376e94d8e2baa7 100644 (file)
--- a/unix/gtkwin.c
+++ b/unix/gtkwin.c
@@ -1422,7 +1422,8 @@ static gint idle_toplevel_callback_func(gpointer data)
         run_toplevel_callbacks();
     }
 
-    gtk_idle_remove(inst->toplevel_callback_idle_id);
+    if (!toplevel_callback_pending())
+        gtk_idle_remove(inst->toplevel_callback_idle_id);
 
     return TRUE;
 }

diff --git a/unix/uxplink.c b/unix/uxplink.c
index 85f91224d6d3a927969f784ce943587760ae801e..ee5cef8aa30f0d50d37f5a99cdacb7f6ec5af679 100644 (file)
--- a/unix/uxplink.c
+++ b/unix/uxplink.c
@@ -979,6 +979,7 @@ int main(int argc, char **argv)
        int maxfd;
        int rwx;
        int ret;
+        unsigned long next;
 
        FD_ZERO(&rset);
        FD_ZERO(&wset);
@@ -1032,12 +1033,17 @@ int main(int argc, char **argv)
                FD_SET_MAX(fd, maxfd, xset);
        }
 
-       do {
-           unsigned long next, then;
-           long ticks;
-           struct timeval tv, *ptv;
+        if (toplevel_callback_pending()) {
+            struct timeval tv;
+            tv.tv_sec = 0;
+            tv.tv_usec = 0;
+            ret = select(maxfd, &rset, &wset, &xset, &tv);
+        } else if (run_timers(now, &next)) {
+            do {
+                unsigned long then;
+                long ticks;
+                struct timeval tv;
 
-           if (run_timers(now, &next)) {
                then = now;
                now = GETTICKCOUNT();
                if (now - then > next - then)
@@ -1046,16 +1052,15 @@ int main(int argc, char **argv)
                    ticks = next - now;
                tv.tv_sec = ticks / 1000;
                tv.tv_usec = ticks % 1000 * 1000;
-               ptv = &tv;
-           } else {
-               ptv = NULL;
-           }
-           ret = select(maxfd, &rset, &wset, &xset, ptv);
-           if (ret == 0)
-               now = next;
-           else
-               now = GETTICKCOUNT();
-       } while (ret < 0 && errno == EINTR);
+                ret = select(maxfd, &rset, &wset, &xset, &tv);
+                if (ret == 0)
+                    now = next;
+                else
+                    now = GETTICKCOUNT();
+            } while (ret < 0 && errno == EINTR);
+        } else {
+            ret = select(maxfd, &rset, &wset, &xset, NULL);
+        }
 
        if (ret < 0) {
            perror("select");

diff --git a/unix/uxsftp.c b/unix/uxsftp.c
index 44e1176401eb3772e6e23b0d0dbe70024afbd291..391da02126233abb52e59276a86d3721a9aef92f 100644 (file)
--- a/unix/uxsftp.c
+++ b/unix/uxsftp.c
@@ -444,6 +444,7 @@ static int ssh_sftp_do_select(int include_stdin, int no_fds_ok)
     int i, fdcount, fdsize, *fdlist;
     int fd, fdstate, rwx, ret, maxfd;
     unsigned long now = GETTICKCOUNT();
+    unsigned long next;
 
     fdlist = NULL;
     fdcount = fdsize = 0;
@@ -488,12 +489,19 @@ static int ssh_sftp_do_select(int include_stdin, int no_fds_ok)
        if (include_stdin)
            FD_SET_MAX(0, maxfd, rset);
 
-       do {
-           unsigned long next, then;
-           long ticks;
-           struct timeval tv, *ptv;
+        if (toplevel_callback_pending()) {
+            struct timeval tv;
+            tv.tv_sec = 0;
+            tv.tv_usec = 0;
+            ret = select(maxfd, &rset, &wset, &xset, &tv);
+            if (ret == 0)
+                run_toplevel_callbacks();
+        } else if (run_timers(now, &next)) {
+            do {
+                unsigned long then;
+                long ticks;
+                struct timeval tv;
 
-           if (run_timers(now, &next)) {
                then = now;
                now = GETTICKCOUNT();
                if (now - then > next - then)
@@ -502,16 +510,15 @@ static int ssh_sftp_do_select(int include_stdin, int no_fds_ok)
                    ticks = next - now;
                tv.tv_sec = ticks / 1000;
                tv.tv_usec = ticks % 1000 * 1000;
-               ptv = &tv;
-           } else {
-               ptv = NULL;
-           }
-           ret = select(maxfd, &rset, &wset, &xset, ptv);
-           if (ret == 0)
-               now = next;
-           else
-               now = GETTICKCOUNT();
-       } while (ret < 0 && errno != EINTR);
+                ret = select(maxfd, &rset, &wset, &xset, &tv);
+                if (ret == 0)
+                    now = next;
+                else
+                    now = GETTICKCOUNT();
+            } while (ret < 0 && errno == EINTR);
+        } else {
+            ret = select(maxfd, &rset, &wset, &xset, NULL);
+        }
     } while (ret == 0);
 
     if (ret < 0) {

diff --git a/windows/window.c b/windows/window.c
index bc89195579f94da84cf248a3b1500e50cfffbba8..ec6ec3e87ffbb9f55155f52b7452f0b4e789a3a9 100644 (file)
--- a/windows/window.c
+++ b/windows/window.c
@@ -847,11 +847,20 @@ int WINAPI WinMain(HINSTANCE inst, HINSTANCE prev, LPSTR cmdline, int show)
     while (1) {
        HANDLE *handles;
        int nhandles, n;
+        DWORD timeout;
+
+        if (toplevel_callback_pending()) {
+            timeout = 0;
+        } else {
+            timeout = INFINITE;
+            /* The messages seem unreliable; especially if we're being tricky */
+            term_set_focus(term, GetForegroundWindow() == hwnd);
+        }
 
        handles = handle_get_events(&nhandles);
 
-       n = MsgWaitForMultipleObjects(nhandles, handles, FALSE, INFINITE,
-                                     QS_ALLINPUT);
+       n = MsgWaitForMultipleObjects(nhandles, handles, FALSE,
+                                      timeout, QS_ALLINPUT);
 
        if ((unsigned)(n - WAIT_OBJECT_0) < (unsigned)nhandles) {
            handle_got_event(handles[n - WAIT_OBJECT_0]);
@@ -859,20 +868,15 @@ int WINAPI WinMain(HINSTANCE inst, HINSTANCE prev, LPSTR cmdline, int show)
        } else
            sfree(handles);
 
-        run_toplevel_callbacks();
-
-       while (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE)) {
+       if (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE)) {
            if (msg.message == WM_QUIT)
                goto finished;         /* two-level break */
 
            if (!(IsWindow(logbox) && IsDialogMessage(logbox, &msg)))
                DispatchMessage(&msg);
-
-            run_toplevel_callbacks();
        }
 
-       /* The messages seem unreliable; especially if we're being tricky */
-       term_set_focus(term, GetForegroundWindow() == hwnd);
+        run_toplevel_callbacks();
     }
 
     finished:

diff --git a/windows/winplink.c b/windows/winplink.c
index 9d29c20b9c3818e4c5279551fc0cdc9f7187065a..a618c7eddd60e36fe64f538695d709dcfcca89ae 100644 (file)
--- a/windows/winplink.c
+++ b/windows/winplink.c
@@ -648,7 +648,9 @@ int main(int argc, char **argv)
            sending = TRUE;
        }
 
-       if (run_timers(now, &next)) {
+        if (toplevel_callback_pending()) {
+            ticks = 0;
+        } else if (run_timers(now, &next)) {
            then = now;
            now = GETTICKCOUNT();
            if (now - then > next - then)

diff --git a/windows/winsftp.c b/windows/winsftp.c
index 23273507e36455883445ec833f0f367e6427bc56..25ac6c9482079b14e0b1218614f02aa77db2430b 100644 (file)
--- a/windows/winsftp.c
+++ b/windows/winsftp.c
@@ -493,7 +493,9 @@ int do_eventsel_loop(HANDLE other_event)
     int skcount;
     unsigned long now = GETTICKCOUNT();
 
-    if (run_timers(now, &next)) {
+    if (toplevel_callback_pending()) {
+        ticks = 0;
+    } else if (run_timers(now, &next)) {
        then = now;
        now = GETTICKCOUNT();
        if (now - then > next - then)