[PATCH] Change py-thread-exited.exp to work with gdbserver

[Tom Tromey <tromey@adacore.com>]

gdbserver does not notify gdb of new threads when they are created.
I'm not sure if this is documented anywhere, but it is mentioned on
this page:

https://sourceware.org/gdb/wiki/LocalRemoteFeatureParity

Search for "Finding new threads in the inferior".

This behavior is a bit unfortunate -- I would think that it would be
better to arrange for such notification if something on the gdb side
is interested.

Meanwhile, this patch fixes py-thread-exited.exp to work around this
problem.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30677
---
 gdb/testsuite/gdb.python/py-thread-exited.c   |  6 +++---
 gdb/testsuite/gdb.python/py-thread-exited.exp | 12 ++++++++++--
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/gdb/testsuite/gdb.python/py-thread-exited.c b/gdb/testsuite/gdb.python/py-thread-exited.c
index fd0342bc765..d62133ba59e 100644
--- a/gdb/testsuite/gdb.python/py-thread-exited.c
+++ b/gdb/testsuite/gdb.python/py-thread-exited.c
@@ -24,14 +24,14 @@ pthread_t thread3_id;
 
 void* do_thread (void* d)
 {
-  return NULL;
+  return NULL;			/* In thread */
 }
 
 int main (void)
 {
   pthread_create (&thread2_id, NULL, do_thread, NULL);
-  pthread_join (thread2_id, NULL);
   pthread_create (&thread3_id, NULL, do_thread, NULL);
+  pthread_join (thread2_id, NULL);
   pthread_join (thread3_id, NULL);
-  return 12;
+  return 12;			/* Done */
 }
diff --git a/gdb/testsuite/gdb.python/py-thread-exited.exp b/gdb/testsuite/gdb.python/py-thread-exited.exp
index 957585958a2..937816106e2 100644
--- a/gdb/testsuite/gdb.python/py-thread-exited.exp
+++ b/gdb/testsuite/gdb.python/py-thread-exited.exp
@@ -36,9 +36,17 @@ if ![runto_main] {
     return -1
 }
 
-gdb_breakpoint 37 "last of main"
 
-gdb_continue_to_breakpoint "continue to breakpoint"
+gdb_breakpoint [gdb_get_line_number "In thread" ${testfile}.c]
+gdb_breakpoint [gdb_get_line_number "Done" ${testfile}.c]
+
+# gdbserver does not notify new threads on creation.  In order for
+# this test to even see that the threads are created, we have to
+# arrange to stop when they are running.
+gdb_continue_to_breakpoint "continue to first in-thread breakpoint"
+gdb_continue_to_breakpoint "continue to second in-thread breakpoint"
+
+gdb_continue_to_breakpoint "continue to end breakpoint"
 
 gdb_test "python print(threadOneExit)" \
 	 ".*event type: thread-exited. global num: 2.*"
-- 
2.40.1