Reliably reset signals at server init time

Each DDX currently calls OsReleaseSIGIO in case it was suspended when
the server regen started. This causes a BUG to occur if SIGIO was
*not* blocked at that time. Instead of relying on each DDX, make the
OS layer reliably reset all signal state at server init time, ensuring
that signals are suitably unblocked and that the various signal state
counting variables are set back to zero.

Signed-off-by: Keith Packard <keithp@keithp.com>

hw/xfree86/common/xf86Init.c

@@ -1012,7 +1012,6 @@ OsVendorInit(void)
     }
 #endif
 #endif
-    OsReleaseSIGIO();
 
     beenHere = TRUE;
 }

include/os.h

@@ -340,6 +340,9 @@ OsBlockSIGIO(void);
 extern _X_EXPORT void
 OsReleaseSIGIO(void);
 
+extern void
+OsResetSignals(void);
+
 extern _X_EXPORT void
 OsAbort(void)
     _X_NORETURN;

os/osinit.c

@@ -288,6 +288,7 @@ OsInit(void)
     }
     TimerInit();
     OsVendorInit();
+    OsResetSignals();
     /*
      * No log file by default.  OsVendorInit() should call LogInit() with the
      * log file name if logging to a file is desired.

os/utils.c

@@ -1243,6 +1243,19 @@ OsReleaseSignals(void)
 #endif
 }
 
+void
+OsResetSignals(void)
+{
+#ifdef SIG_BLOCK
+    while (BlockedSignalCount > 0)
+        OsReleaseSignals();
+#ifdef SIGIO
+    while (sigio_blocked > 0)
+        OsReleaseSIGIO();
+#endif
+#endif
+}
+
 /*
  * Pending signals may interfere with core dumping. Provide a
  * mechanism to block signals when aborting.