From 67fc5d68f967d19236221b2c0c2e0fe45acf560f Mon Sep 17 00:00:00 2001
From: Keith Packard <keithp@keithp.com>
Date: Sat, 13 Aug 2016 09:02:15 -0700
Subject: [PATCH] os: Abandon loop after poll call when array of fds has
 changed

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@keithp.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
---
 os/ospoll.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/os/ospoll.c b/os/ospoll.c
index 2996ac7f4..b00d42202 100644
--- a/os/ospoll.c
+++ b/os/ospoll.c
@@ -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;
             }
         }
     }