[PATCH] os: add -sigstop option for Upstart (or equivalent) startup

[Tiago Vignatti]

From: Oliver Mcfadden <oliver.mcfadden at nokia.com>

This is very similar to the RunFromSmartParent (implicit) option, except
we do not send the signal to our parent process, but our own process
instead, and that signal is SIGSTOP, not SIGUSR1.

Upstart or a similar equivalent program will detect this, realize that
we are ready to accept clients now, send us SIGCONT and move our job
status from SPAWNED to RUNNING.

Signed-off-by: Oliver McFadden <oliver.mcfadden at nokia.com>
Acked-by: Peter Hutterer <peter.hutterer at who-t.net>
Signed-off-by: Tiago Vignatti <tiago.vignatti at nokia.com>
---
Keith, can you please pull this one?

 include/opaque.h |    1 +
 os/connection.c  |    4 ++++
 os/utils.c       |    5 +++++
 3 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/include/opaque.h b/include/opaque.h
index b3c7c70..dfe440c 100644
--- a/include/opaque.h
+++ b/include/opaque.h
@@ -55,6 +55,7 @@ extern _X_EXPORT int defaultBackingStore;
 extern _X_EXPORT Bool disableBackingStore;
 extern _X_EXPORT Bool enableBackingStore;
 extern _X_EXPORT Bool PartialNetwork;
+extern _X_EXPORT Bool RunFromSigStopParent;
 #ifndef NOLOGOHACK
 extern _X_EXPORT int logoScreenSaver;
 #endif
diff --git a/os/connection.c b/os/connection.c
index 77910be..28cd193 100644
--- a/os/connection.c
+++ b/os/connection.c
@@ -146,6 +146,8 @@ Bool NewOutputPending;		/* not yet attempted to write some new output */
 Bool AnyClientsWriteBlocked;	/* true if some client blocked on write */
 
 static Bool RunFromSmartParent;	/* send SIGUSR1 to parent process */
+Bool RunFromSigStopParent;	/* send SIGSTOP to our own process; Upstart (or
+				   equivalent) will send SIGCONT back. */
 Bool PartialNetwork;	/* continue even if unable to bind all addrs */
 static Pid_t ParentProcess;
 
@@ -357,6 +359,8 @@ NotifyParentProcess(void)
 	    kill (ParentProcess, SIGUSR1);
 	}
     }
+    if (RunFromSigStopParent)
+	raise (SIGSTOP);
 #endif
 }
 
diff --git a/os/utils.c b/os/utils.c
index 51455cc..f30674b 100644
--- a/os/utils.c
+++ b/os/utils.c
@@ -527,6 +527,7 @@ void UseMsg(void)
 #endif
     ErrorF("-dumbSched             Disable smart scheduling, enable old behavior\n");
     ErrorF("-schedInterval int     Set scheduler interval in msec\n");
+    ErrorF("-sigstop               Enable SIGSTOP based startup\n");
     ErrorF("+extension name        Enable extension\n");
     ErrorF("-extension name        Disable extension\n");
 #ifdef XDMCP
@@ -922,6 +923,10 @@ ProcessCommandLine(int argc, char *argv[])
 	    else
 		UseMsg ();
 	}
+	else if ( strcmp( argv[i], "-sigstop") == 0)
+	{
+	    RunFromSigStopParent = TRUE;
+	}
 	else if ( strcmp( argv[i], "+extension") == 0)
 	{
 	    if (++i < argc)
-- 
1.7.1.226.g770c5