[RFA] Make watchthreads.exp more robust

[dje@google.com (Doug Evans)]

Hi.

watchthreads.exp can errantly fail if the o/s schedules, for example,
the thread for args[0] enough times before the thread for args[1] gets
a chance to run.

Ok to check in?

2009-04-26  Doug Evans  <dje@google.com>

	* gdb.threads/watchthreads.c (main): Initialize args before starting
	the threads.  Plus formatting cleanup.
	* gdb.threads/watchthreads.exp: Avoid errant failures due to
	biased scheduling of one thread.

Index: watchthreads.c
===================================================================
RCS file: /cvs/src/src/gdb/testsuite/gdb.threads/watchthreads.c,v
retrieving revision 1.6
diff -u -p -u -p -r1.6 watchthreads.c
--- watchthreads.c	3 Jan 2009 05:58:07 -0000	1.6
+++ watchthreads.c	26 Apr 2009 18:54:22 -0000
@@ -22,34 +22,49 @@
 #include <stdlib.h>
 #include <pthread.h>
 
-void *thread_function(void *arg); /* Pointer to function executed by each thread */
+void *thread_function (void *arg); /* Function executed by each thread.  */
 
 #define NUM 5
 
 unsigned int args[NUM+1];
 
-int main() {
+int
+main ()
+{
     int res;
     pthread_t threads[NUM];
     void *thread_result;
     long i;
 
+    /* To keep the test determinative, initialize args first,
+       then start all the threads.  Otherwise, the way watchthreads.exp
+       is written, we have to worry about things like threads[0] getting
+       to 29 hits of args[0] before args[1] gets changed.  */
+
+    for (i = 0; i < NUM; i++)
+      {
+	/* The call to usleep is so that when the watchpoint triggers,
+	   the pc is still on the same line.  */
+	args[i] = 1; usleep (1); /* Init value.  */
+      }
+
     for (i = 0; i < NUM; i++)
       {
-	args[i] = 1; /* Init value.  */
-	res = pthread_create(&threads[i],
-		             NULL,
-			     thread_function,
-			     (void *) i);
+	res = pthread_create (&threads[i],
+			      NULL,
+			      thread_function,
+			      (void *) i);
       }
 
     args[i] = 1;
     thread_function ((void *) i);
 
-    exit(EXIT_SUCCESS);
+    exit (EXIT_SUCCESS);
 }
 
-void *thread_function(void *arg) {
+void *
+thread_function (void *arg)
+{
     int my_number =  (long) arg;
     int *myp = (int *) &args[my_number];
 
@@ -59,6 +74,6 @@ void *thread_function(void *arg) {
 	(*myp) ++; usleep (1);  /* Loop increment.  */
       }
 
-    pthread_exit(NULL);
+    pthread_exit (NULL);
 }
 
Index: watchthreads.exp
===================================================================
RCS file: /cvs/src/src/gdb/testsuite/gdb.threads/watchthreads.exp,v
retrieving revision 1.7
diff -u -p -u -p -r1.7 watchthreads.exp
--- watchthreads.exp	3 Jan 2009 05:58:07 -0000	1.7
+++ watchthreads.exp	26 Apr 2009 18:54:22 -0000
@@ -62,8 +62,10 @@ set args_1 0
 # Watch values that will be modified by distinct threads.
 gdb_test "watch args\[0\]" "Hardware watchpoint 2: args\\\[0\\\]"
 gdb_test "watch args\[1\]" "Hardware watchpoint 3: args\\\[1\\\]"
+set hwwp_2_enabled 1
+set hwwp_3_enabled 1
 
-set init_line [expr [gdb_get_line_number "Init value"]+1]
+set init_line [gdb_get_line_number "Init value"]
 set inc_line [gdb_get_line_number "Loop increment"]
 set main_loc "main \\\(\\\) at .*watchthreads.c:$init_line"
 set thread0_loc "thread_function \\\(arg=0x0\\\) at .*watchthreads.c:$inc_line"
@@ -114,6 +116,27 @@ for {set i 0} {$i < 30} {incr i} {
 	} else {
 	    fail "threaded watch loop"
 	}
+
+	# If one of the watchpoints is disabled, we'd better not stop there.
+	if { !$hwwp_2_enabled && $test_flag_0 } {
+	    fail "disabled hw watchpoint 2 triggered"
+	}
+	if { !$hwwp_3_enabled && $test_flag_1 } {
+	    fail "disabled hw watchpoint 3 triggered"
+	}
+
+	# If we get to 10 in one of the watched locations disable it so we
+	# see some of the other watched location.
+	# 10 is chosen so we're guaranteed to come through here.
+	if { $hwwp_2_enabled && $hwwp_3_enabled } {
+	    if { $args_0 >= 10 && $hwwp_2_enabled } {
+		gdb_test "disable 2" ""
+		set hwwp_2_enabled 0
+	    } elseif { $args_1 >= 10 && $hwwp_3_enabled } {
+		gdb_test "disable 3" ""
+		set hwwp_3_enabled 0
+	    }
+	}
     }
   }