Add backlink from lwp_info to thread_info.

* gdbthread.h (add_thread): Change result type to struct thread_info *.
	* inferiors.c (add_thread): Change result type to struct thread_info *.
	All callers updated.
	(add_lwp): Call add_thread here instead of in callers.
	All callers updated.
	* linux-low.h (get_lwp_thread): Rewrite.
	(struct lwp_info): New member "thread".

This speeds up gdbserver attach in non-stop mode because now get_lwp_thread
doesn't do a linear search for the corresponding thread_info object.

gdb/gdbserver/ChangeLog

@@ -1,3 +1,13 @@
+2014-02-19  Doug Evans  <dje@google.com>
+
+	* gdbthread.h (add_thread): Change result type to struct thread_info *.
+	* inferiors.c (add_thread): Change result type to struct thread_info *.
+	All callers updated.
+	(add_lwp): Call add_thread here instead of in callers.
+	All callers updated.
+	* linux-low.h (get_lwp_thread): Rewrite.
+	(struct lwp_info): New member "thread".
+
 2014-02-19  Doug Evans  <dje@google.com>
 
 	* linux-low.c (add_lwp): Change result to struct lwp_info *.

gdb/gdbserver/gdbthread.h

@@ -74,7 +74,7 @@ struct thread_info
 extern struct inferior_list all_threads;
 
 void remove_thread (struct thread_info *thread);
-void add_thread (ptid_t ptid, void *target_data);
+struct thread_info *add_thread (ptid_t ptid, void *target_data);
 
 struct thread_info *get_first_thread (void);
 

gdb/gdbserver/inferiors.c

@@ -104,7 +104,7 @@ remove_inferior (struct inferior_list *list,
     list->tail = *cur;
 }
 
-void
+struct thread_info *
 add_thread (ptid_t thread_id, void *target_data)
 {
   struct thread_info *new_thread = xmalloc (sizeof (*new_thread));
@@ -121,6 +121,8 @@ add_thread (ptid_t thread_id, void *target_data)
     current_inferior = new_thread;
 
   new_thread->target_data = target_data;
+
+  return new_thread;
 }
 
 ptid_t

gdb/gdbserver/linux-low.c

@@ -409,7 +409,6 @@ handle_extended_wait (struct lwp_info *event_child, int wstat)
 
       ptid = ptid_build (pid_of (event_child), new_pid, 0);
       new_lwp = add_lwp (ptid);
-      add_thread (ptid, new_lwp);
 
       /* Either we're going to immediately resume the new thread
 	 or leave it stopped.  linux_resume_one_lwp is a nop if it
@@ -539,6 +538,7 @@ add_lwp (ptid_t ptid)
     lwp->arch_private = the_low_target.new_thread ();
 
   add_inferior_to_list (&all_lwps, &lwp->entry);
+  lwp->thread = add_thread (ptid, lwp);
 
   return lwp;
 }
@@ -632,7 +632,6 @@ linux_create_inferior (char *program, char **allargs)
 
   ptid = ptid_build (pid, pid, 0);
   new_lwp = add_lwp (ptid);
-  add_thread (ptid, new_lwp);
   new_lwp->must_set_ptrace_flags = 1;
 
   return pid;
@@ -683,7 +682,6 @@ linux_attach_lwp_1 (unsigned long lwpid, int initial)
     }
 
   new_lwp = add_lwp (ptid);
-  add_thread (ptid, new_lwp);
 
   /* We need to wait for SIGSTOP before being able to make the next
      ptrace call on this LWP.  */

gdb/gdbserver/linux-low.h

@@ -229,14 +229,17 @@ extern struct linux_target_ops the_low_target;
 
 #define get_lwp(inf) ((struct lwp_info *)(inf))
 #define get_thread_lwp(thr) (get_lwp (inferior_target_data (thr)))
-#define get_lwp_thread(proc) ((struct thread_info *)			\
-			      find_inferior_id (&all_threads,		\
-						get_lwp (proc)->entry.id))
+#define get_lwp_thread(lwp) ((lwp)->thread)
 
 struct lwp_info
 {
   struct inferior_list_entry entry;
 
+  /* Backlink to the thread_info object.
+     It is the "main" representation of the thread, we just contain
+     linux-specific subordinate data.  */
+  struct thread_info *thread;
+
   /* If this flag is set, the next SIGSTOP will be ignored (the
      process will be immediately resumed).  This means that either we
      sent the SIGSTOP to it ourselves and got some other pending event