qa: check that notes cannot eat wait messages

qa/kern/build.json

@@ -40,6 +40,7 @@
 			"syscall.c",
 			"sysstatread.c",
 			"tsemacquire.c",
+			"wait_note.c",
 			"waserror.c"
 		]
 	}

qa/kern/wait_note.c

@@ -0,0 +1,72 @@
+/*
+ * This file is part of Jehanne.
+ *
+ * Copyright (C) 2017 Giacomo Tesio <giacomo@tesio.it>
+ *
+ * Jehanne is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 2 of the License.
+ *
+ * Jehanne is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Jehanne.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include <u.h>
+#include <lib9.h>
+
+int
+ignore_note(void *v, char *s)
+{
+	print("%d: note received: %s\n", getpid(), s);
+	return 1;
+}
+
+void
+main(void)
+{
+	Waitmsg *w;
+	int i = 0, cpid;
+
+	if (!atnotify(ignore_note, 1)){
+		fprint(2, "%r\n");
+		exits("atnotify fails");
+	}
+	switch(cpid = fork()){
+	case -1:
+		print("FAIL: fork\n");
+		exits("FAIL");
+	case 0:
+		print("%d: child: waiting 3 sec\n", getpid());
+		sleep(3000);
+		print("%d: child: sending note to parent\n", getpid());
+		postnote(PNPROC, getppid(), "test");
+		exits(0);
+	default:
+		break;
+	}
+	print("%d: start waiting for child to complete\n", getpid());
+InterruptedByNote:
+	w = wait();
+	if(w == nil){
+		if(i==0){
+			++i;
+			print("%d: wait interrupted by note, try again once\n", getpid());
+			goto InterruptedByNote;
+		}
+		print("FAIL: no wait msg\n");
+		exits("FAIL");
+	}
+
+	if(cpid != w->pid){
+		print("FAIL: wrong Waitmsg: pid = %d instead of expected %d\n", w->pid, cpid);
+		exits("FAIL");
+	}
+	print("Got Waitmsg for child %d\n", w->pid);
+
+	print("PASS\n");
+	exits("PASS");
+}