remote.c: Use the ptid.lwp field to store remote thread ids rather than ptid.tid.

From GDB's perspective, independently of how the target really
implements threads, gdb/remote sees all threads as if kernel/system
threads.  A rationale along theses lines led to gdbserver storing
thread ids in ptid.lwp in all ports.

Because remote.c is currently using ptid.tid, we can't make gdbserver
and gdb share bits of remote-specific code that manipulates ptids
(e.g., write_ptid/read_ptid).

This patch thus makes remote.c use ptid.lwp instead of ptid.tid.

I believe that on the GDB side too, it's best that we standardize on
process_stratum targets using the ptid.lwp field to store thread ids
anyway.  The idea being leave the ptid.tid field free for any
thread_stratum target that might want to sit on top.

Tested on x86_64 Fedora 17, w/ local gdbserver.

gdb/
2014-02-19  Pedro Alves  <palves@redhat.com>

	* remote.c (remote_thread_alive, write_ptid, read_ptid)
	(read_ptid, remote_newthread_step, remote_threads_extra_info)
	(remote_get_ada_task_ptid, append_resumption, remote_stop_ns)
	(threadalive_test, remote_pid_to_str): Use the ptid.lwp field to
	store remote thread ids rather than ptid.tid.
	(_initialize_remote): Adjust.

2 files changed, 26 insertions, 17 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 9fbd6dd..122288d 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,12 @@
+2014-02-19  Pedro Alves  <palves@redhat.com>
+
+	* remote.c (remote_thread_alive, write_ptid, read_ptid)
+	(read_ptid, remote_newthread_step, remote_threads_extra_info)
+	(remote_get_ada_task_ptid, append_resumption, remote_stop_ns)
+	(threadalive_test, remote_pid_to_str): Use the ptid.lwp field to
+	store remote thread ids rather than ptid.tid.
+	(_initialize_remote): Adjust.
+
 2014-02-19  Tom Tromey  <tromey@redhat.com>
 
 	* target.c (target_get_unwinder): Rewrite.
diff --git a/gdb/remote.c b/gdb/remote.c
index 537221a..dcf2e50 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -1879,7 +1879,7 @@ remote_thread_alive (struct target_ops *ops, ptid_t ptid)
     /* The main thread is always alive.  */
     return 1;
 
-  if (ptid_get_pid (ptid) != 0 && ptid_get_tid (ptid) == 0)
+  if (ptid_get_pid (ptid) != 0 && ptid_get_lwp (ptid) == 0)
     /* The main thread is always alive.  This can happen after a
        vAttach, if the remote side doesn't support
        multi-threading.  */
@@ -2017,7 +2017,7 @@ write_ptid (char *buf, const char *endbuf, ptid_t ptid)
       else
 	buf += xsnprintf (buf, endbuf - buf, "p%x.", pid);
     }
-  tid = ptid_get_tid (ptid);
+  tid = ptid_get_lwp (ptid);
   if (tid < 0)
     buf += xsnprintf (buf, endbuf - buf, "-%x", -tid);
   else
@@ -2047,7 +2047,7 @@ read_ptid (char *buf, char **obuf)
       pp = unpack_varlen_hex (p + 1, &tid);
       if (obuf)
 	*obuf = pp;
-      return ptid_build (pid, 0, tid);
+      return ptid_build (pid, tid, 0);
     }
 
   /* No multi-process.  Just a tid.  */
@@ -2064,7 +2064,7 @@ read_ptid (char *buf, char **obuf)
 
   if (obuf)
     *obuf = pp;
-  return ptid_build (pid, 0, tid);
+  return ptid_build (pid, tid, 0);
 }
 
 static int
@@ -2557,7 +2557,7 @@ static int
 remote_newthread_step (threadref *ref, void *context)
 {
   int pid = ptid_get_pid (inferior_ptid);
-  ptid_t ptid = ptid_build (pid, 0, threadref_to_int (ref));
+  ptid_t ptid = ptid_build (pid, threadref_to_int (ref), 0);
 
   if (!in_thread_list (ptid))
     add_thread (ptid);
@@ -2826,7 +2826,7 @@ remote_threads_extra_info (struct target_ops *self, struct thread_info *tp)
 		    _("remote_threads_extra_info"));
 
   if (ptid_equal (tp->ptid, magic_null_ptid)
-      || (ptid_get_pid (tp->ptid) != 0 && ptid_get_tid (tp->ptid) == 0))
+      || (ptid_get_pid (tp->ptid) != 0 && ptid_get_lwp (tp->ptid) == 0))
     /* This is the main thread which was added by GDB.  The remote
        server doesn't know about it.  */
     return NULL;
@@ -2865,7 +2865,7 @@ remote_threads_extra_info (struct target_ops *self, struct thread_info *tp)
   rs->use_threadextra_query = 0;
   set = TAG_THREADID | TAG_EXISTS | TAG_THREADNAME
     | TAG_MOREDISPLAY | TAG_DISPLAY;
-  int_to_threadref (&id, ptid_get_tid (tp->ptid));
+  int_to_threadref (&id, ptid_get_lwp (tp->ptid));
   if (remote_get_threadinfo (&id, set, &threadinfo))
     if (threadinfo.active)
       {
@@ -2975,7 +2975,7 @@ remote_static_tracepoint_markers_by_strid (struct target_ops *self,
 static ptid_t
 remote_get_ada_task_ptid (struct target_ops *self, long lwp, long thread)
 {
-  return ptid_build (ptid_get_pid (inferior_ptid), 0, lwp);
+  return ptid_build (ptid_get_pid (inferior_ptid), lwp, 0);
 }
 
 
@@ -4725,7 +4725,7 @@ append_resumption (char *p, char *endp,
       ptid_t nptid;
 
       /* All (-1) threads of process.  */
-      nptid = ptid_build (ptid_get_pid (ptid), 0, -1);
+      nptid = ptid_build (ptid_get_pid (ptid), -1, 0);
 
       p += xsnprintf (p, endp - p, ":");
       p = write_ptid (p, endp, nptid);
@@ -5040,7 +5040,7 @@ remote_stop_ns (ptid_t ptid)
 
       if (ptid_is_pid (ptid))
 	  /* All (-1) threads of process.  */
-	nptid = ptid_build (ptid_get_pid (ptid), 0, -1);
+	nptid = ptid_build (ptid_get_pid (ptid), -1, 0);
       else
 	{
 	  /* Small optimization: if we already have a stop reply for
@@ -9113,7 +9113,7 @@ threadalive_test (char *cmd, int tty)
 {
   int sample_thread = SAMPLE_THREAD;
   int pid = ptid_get_pid (inferior_ptid);
-  ptid_t ptid = ptid_build (pid, 0, sample_thread);
+  ptid_t ptid = ptid_build (pid, sample_thread, 0);
 
   if (remote_thread_alive (ptid))
     printf_filtered ("PASS: Thread alive test\n");
@@ -9261,10 +9261,10 @@ remote_pid_to_str (struct target_ops *ops, ptid_t ptid)
 	xsnprintf (buf, sizeof buf, "Thread <main>");
       else if (rs->extended && remote_multi_process_p (rs))
 	xsnprintf (buf, sizeof buf, "Thread %d.%ld",
-		   ptid_get_pid (ptid), ptid_get_tid (ptid));
+		   ptid_get_pid (ptid), ptid_get_lwp (ptid));
       else
 	xsnprintf (buf, sizeof buf, "Thread %ld",
-		   ptid_get_tid (ptid));
+		   ptid_get_lwp (ptid));
       return buf;
     }
 }
@@ -12150,11 +12150,11 @@ stepping is supported by the target.  The default is on."),
   /* Eventually initialize fileio.  See fileio.c */
   initialize_remote_fileio (remote_set_cmdlist, remote_show_cmdlist);
 
-  /* Take advantage of the fact that the LWP field is not used, to tag
+  /* Take advantage of the fact that the TID field is not used, to tag
      special ptids with it set to != 0.  */
-  magic_null_ptid = ptid_build (42000, 1, -1);
-  not_sent_ptid = ptid_build (42000, 1, -2);
-  any_thread_ptid = ptid_build (42000, 1, 0);
+  magic_null_ptid = ptid_build (42000, -1, 1);
+  not_sent_ptid = ptid_build (42000, -2, 1);
+  any_thread_ptid = ptid_build (42000, 0, 1);
 
   target_buf_size = 2048;
   target_buf = xmalloc (target_buf_size);