[PATCH xserver 2/2] os: Abandon loop after poll call when array of fds has changed

[Keith Packard]

If a file descriptor is added or removed from an ospoll callback, then
the arrays containing file descriptor information will have all of
their indices changed, so the loop state is no longer consistent. Just
bail out and let the caller come back around to try again.

Signed-off-by: Keith Packard <keithp at keithp.com>
---
 os/ospoll.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/os/ospoll.c b/os/ospoll.c
index 2996ac7..902294d 100644
--- a/os/ospoll.c
+++ b/os/ospoll.c
@@ -32,7 +32,7 @@
 #include "ospoll.h"
 #include "list.h"
 
-#if !HAVE_OSPOLL && HAVE_EPOLL_CREATE1
+#if !HAVE_OSPOLL && HAVE_EPOLL_CREATE1 && 0
 #include <sys/epoll.h>
 #define EPOLL           1
 #define HAVE_OSPOLL     1
@@ -82,6 +82,7 @@ struct ospoll {
     struct ospollfd     *osfds;
     int                 num;
     int                 size;
+    Bool                changed;
 };
 
 #endif
@@ -279,6 +280,7 @@ ospoll_add(struct ospoll *ospoll, int fd,
         array_insert(ospoll->fds, ospoll->num, sizeof (ospoll->fds[0]), pos);
         array_insert(ospoll->osfds, ospoll->num, sizeof (ospoll->osfds[0]), pos);
         ospoll->num++;
+        ospoll->changed = TRUE;
 
         ospoll->fds[pos].fd = fd;
         ospoll->fds[pos].events = 0;
@@ -316,6 +318,7 @@ ospoll_remove(struct ospoll *ospoll, int fd)
         array_delete(ospoll->fds, ospoll->num, sizeof (ospoll->fds[0]), pos);
         array_delete(ospoll->osfds, ospoll->num, sizeof (ospoll->osfds[0]), pos);
         ospoll->num--;
+        ospoll->changed = TRUE;
 #endif
     }
 }
@@ -408,6 +411,7 @@ ospoll_wait(struct ospoll *ospoll, int timeout)
 #endif
 #if POLL
     nready = xserver_poll(ospoll->fds, ospoll->num, timeout);
+    ospoll->changed = FALSE;
     if (nready > 0) {
         int f;
         for (f = 0; f < ospoll->num; f++) {
@@ -427,6 +431,12 @@ ospoll_wait(struct ospoll *ospoll, int timeout)
                     xevents |= X_NOTIFY_ERROR;
                 ospoll->osfds[f].callback(ospoll->fds[f].fd, xevents,
                                           ospoll->osfds[f].data);
+
+                /* Check to see if the arrays have changed, and just go back
+                 * around again
+                 */
+                if (ospoll->changed)
+                    break;
             }
         }
     }
-- 
2.8.1