From: Egbert Eich <eich@freedesktop.org>
Date: Fri Jan 29 11:05:46 2016 +0100
Subject: [PATCH]os/connections: Check for stale FDs
Patch-mainline: to be upstreamed
Git-repo: git://anongit.freedesktop.org/git/xorg/xserver
References: bsc#954433
Signed-off-by: Egbert Eich <eich@suse.com>

So far we've only checked for stale client connections.
However, our main select loop checks file descriptors
of devices and sockets of services like dbus.

These file descriptors may become stale as well, for instance,
when the underlying service has died. In this case, select
will return immediately with EBADF. Without removing these
stale FDs, the Xserver will loop rapidly in WaitFor().

Thus, simply remove the respective bit from AllSockets.

Signed-off-by: Egbert Eich <eich@freedesktop.org>
---
 include/os.h    |  3 +++
 os/WaitFor.c    |  5 +++++
 os/connection.c | 37 +++++++++++++++++++++++++++++++++++++
 3 files changed, 45 insertions(+)

diff --git a/include/os.h b/include/os.h
index 11af73f..a4c2f56 100644
--- a/include/os.h
+++ b/include/os.h
@@ -51,6 +51,7 @@ SOFTWARE.
 #include <stdarg.h>
 #include <stdint.h>
 #include <string.h>
+#include <sys/select.h>
 #ifdef MONOTONIC_CLOCK
 #include <time.h>
 #endif
@@ -147,6 +148,8 @@ extern _X_EXPORT Bool EstablishNewConnections(ClientPtr clientUnused,
 
 extern _X_EXPORT void CheckConnections(void);
 
+extern _X_EXPORT void CheckFDs(fd_set *);
+
 extern _X_EXPORT void CloseDownConnection(ClientPtr /*client */ );
 
 extern _X_EXPORT void AddGeneralSocket(int /*fd */ );
diff --git a/os/WaitFor.c b/os/WaitFor.c
index 993c14e..01e864d 100644
--- a/os/WaitFor.c
+++ b/os/WaitFor.c
@@ -233,7 +233,12 @@ WaitForSomething(int *pClientsReady)
                 return 0;
             if (i < 0) {
                 if (selecterr == EBADF) {       /* Some client disconnected */
+                    fd_set mask;
+                    XFD_COPYSET(&LastSelectMask, &mask);
+                    XFD_UNSET(&mask, &AllClients);
                     CheckConnections();
+                    if (XFD_ANYSET(&mask))
+                        CheckFDs(&mask);
                     if (!XFD_ANYSET(&AllClients))
                         return 0;
                 }
diff --git a/os/connection.c b/os/connection.c
index 9c41c7c..d67f1ef 100644
--- a/os/connection.c
+++ b/os/connection.c
@@ -1036,6 +1036,43 @@ CheckConnections(void)
 }
 
 /*****************
+ * CheckFDs
+ *****************/
+void
+CheckFDs(fd_set *fdbits)
+{
+    fd_mask mask;
+    fd_set tmask;
+    int curbit, curoff;
+    int i;
+    struct timeval notime;
+    int r;
+    notime.tv_sec = 0;
+    notime.tv_usec = 0;
+
+    for (i = 0; i < howmany(XFD_SETSIZE, NFDBITS); i++) {
+        mask = fdbits->fds_bits[i];
+        while (mask) {
+            curoff = mffs(mask) - 1;
+            curbit = curoff + (i * (sizeof(fd_mask) * 8));
+            FD_ZERO(&tmask);
+            FD_SET(curbit, &tmask);
+            do {
+                r = Select(curbit + 1, &tmask, NULL, NULL, &notime);
+            } while (r < 0 && (errno == EINTR || errno == EAGAIN));
+            if (r < 0 && errno == EBADF) {
+                //RemoveNotifyFd(curbit);
+                FD_CLR(curbit, &EnabledDevices);
+                FD_CLR(curbit, &AllSockets);
+                if (GrabInProgress)
+                    FD_CLR(curbit, &SavedAllSockets);
+            }
+            mask &= ~((fd_mask) 1 << curoff);
+        }
+    }
+}
+
+/*****************
  * CloseDownConnection
  *    Delete client from AllClients and free resources
  *****************/