[Xen-changelog] Fix xenconsoled when sending lots of console data to a domU.

[Xen patchbot -unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User kaf24@xxxxxxxxxxxxxxxxxxxx
# Node ID 7c994d80049c1a3003623b56c9667ca37fdd8b04
# Parent  9239f190736d85933bbe64eca0613c24c07617df
Fix xenconsoled when sending lots of console data to a domU.
Fixes bug #477.

Signed-off-by: Keir Fraser <keir@xxxxxxxxxxxxx>

diff -r 9239f190736d -r 7c994d80049c tools/console/daemon/io.c
--- a/tools/console/daemon/io.c Wed Mar 29 23:11:53 2006
+++ b/tools/console/daemon/io.c Thu Mar 30 10:38:56 2006
@@ -434,25 +434,36 @@
        }
 }
 
+static int ring_free_bytes(struct domain *dom)
+{
+       struct xencons_interface *intf = dom->interface;
+       XENCONS_RING_IDX cons, prod, space;
+
+       cons = intf->in_cons;
+       prod = intf->in_prod;
+       mb();
+
+       space = prod - cons;
+       if (space > sizeof(intf->in))
+               return 0; /* ring is screwed: ignore it */
+
+       return (sizeof(intf->in) - space);
+}
+
 static void handle_tty_read(struct domain *dom)
 {
        ssize_t len = 0;
        char msg[80];
        int i;
        struct xencons_interface *intf = dom->interface;
-       XENCONS_RING_IDX cons, prod;
-
-       cons = intf->in_cons;
-       prod = intf->in_prod;
-       mb();
-
-       if (sizeof(intf->in) > (prod - cons))
-               len = sizeof(intf->in) - (prod - cons);
+       XENCONS_RING_IDX prod;
+
+       len = ring_free_bytes(dom);
+       if (len == 0)
+               return;
+
        if (len > sizeof(msg))
                len = sizeof(msg);
-
-       if (len == 0)
-               return;
 
        len = read(dom->tty_fd, msg, len);
        if (len < 1) {
@@ -465,6 +476,7 @@
                        shutdown_domain(dom);
                }
        } else if (domain_is_valid(dom->domid)) {
+               prod = intf->in_prod;
                for (i = 0; i < len; i++) {
                        intf->in[MASK_XENCONS_IDX(prod++, intf->in)] =
                                msg[i];
@@ -514,7 +526,7 @@
        (void)write_sync(dom->evtchn_fd, &v, sizeof(v));
 }
 
-static void handle_xs(int fd)
+static void handle_xs(void)
 {
        char **vec;
        int domid;
@@ -560,7 +572,7 @@
                        }
 
                        if (d->tty_fd != -1) {
-                               if (!d->is_dead)
+                               if (!d->is_dead && ring_free_bytes(d))
                                        FD_SET(d->tty_fd, &readfds);
 
                                if (!buffer_empty(&d->buffer))
@@ -572,7 +584,7 @@
                ret = select(max_fd + 1, &readfds, &writefds, 0, NULL);
 
                if (FD_ISSET(xs_fileno(xs), &readfds))
-                       handle_xs(xs_fileno(xs));
+                       handle_xs();
 
                for (d = dom_head; d; d = n) {
                        n = d->next;

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