[PATCH 03/18] remote.c/all-stop: Implement TARGET_WAITKIND_NO_RESUMED and TARGET_WNOHANG

[Pedro Alves <palves@redhat.com>]

Even though "target remote" supports target-async, the all-stop
target_wait implementation ignores TARGET_WNOHANG.  If the core
happens to poll for events and we've already read the stop reply out
of the serial/socket, remote_wait_as hangs forever instead of
returning an indication that there are no events to process.  This
can't happen currently, but later changes will trigger this.

gdb/ChangeLog:
2015-05-21  Pedro Alves  <palves@redhat.com>

	* remote.c (remote_wait_as): If not waiting for a stop reply,
	return TARGET_WAITKIND_NO_RESUMED.  If TARGET_WNOHANG is
	requested, don't block waiting forever.
---
 gdb/remote.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/gdb/remote.c b/gdb/remote.c
index dfe115b..db06def 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -6227,6 +6227,14 @@ remote_wait_as (ptid_t ptid, struct target_waitstatus *status, int options)
     {
       int ret;
       int is_notif;
+      int forever = ((options & TARGET_WNOHANG) == 0
+		     && wait_forever_enabled_p);
+
+      if (!rs->waiting_for_stop_reply)
+	{
+	  status->kind = TARGET_WAITKIND_NO_RESUMED;
+	  return minus_one_ptid;
+	}
 
       if (!target_is_async_p ())
 	{
@@ -6245,7 +6253,7 @@ remote_wait_as (ptid_t ptid, struct target_waitstatus *status, int options)
 	 However, before we do that we need to ensure that the caller
 	 knows how to take the target into/out of async mode.  */
       ret = getpkt_or_notif_sane (&rs->buf, &rs->buf_size,
-				  wait_forever_enabled_p, &is_notif);
+				  forever, &is_notif);
 
       if (!target_is_async_p ())
 	signal (SIGINT, ofunc);
@@ -6254,6 +6262,9 @@ remote_wait_as (ptid_t ptid, struct target_waitstatus *status, int options)
 	 not interesting.  */
       if (ret != -1 && is_notif)
 	return minus_one_ptid;
+
+      if (ret == -1 && (options & TARGET_WNOHANG) != 0)
+	return minus_one_ptid;
     }
 
   buf = rs->buf;
-- 
1.9.3