bitbake: process/cooker: Improve readypipe handling

Issues in start are not being correctly detected by the current readypipe
code. Change it to use specific "ready" or "fail" messages to correctly
determine the correct failure mode and avoid bitbake seeming to hang
(it does currently timeout eventually).

[YOCTO #12062]

(Bitbake rev: 60d4791e3dd05729d2a2adf6f3b203c80d466a73)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/server/process.py

@@ -388,8 +388,10 @@ class BitBakeServer(object):
         self.bitbake_lock.close()
 
         ready = ConnectionReader(self.readypipe)
-        r = ready.wait(30)
-        if not r:
+        r = ready.poll(30)
+        if r:
+            r = ready.get()
+        if not r or r != "ready":
             ready.close()
             bb.error("Unable to start bitbake server")
             if os.path.exists(logfile):
@@ -404,8 +406,15 @@ class BitBakeServer(object):
         print("Starting bitbake server pid %d" % os.getpid())
         server = ProcessServer(self.bitbake_lock, self.sock, self.sockname)
         self.configuration.setServerRegIdleCallback(server.register_idle_function)
-
-        self.cooker = bb.cooker.BBCooker(self.configuration, self.featureset, self.readypipein)
+        writer = ConnectionWriter(self.readypipein)
+        try:
+            self.cooker = bb.cooker.BBCooker(self.configuration, self.featureset)
+            writer.send("ready")
+        except:
+            writer.send("fail")
+            raise
+        finally:
+            os.close(self.readypipein)
         server.cooker = self.cooker
         server.server_timeout = self.configuration.server_timeout
         server.xmlrpcinterface = self.configuration.xmlrpcinterface