[binutils-gdb] Fix reconnecting to a gdbserver already debugging multiple processes, II

[gdb-buildbot@sergiodj.net]

*** TEST RESULTS FOR COMMIT 75c6c844d9df37761e0e834df057b89e41816e55 ***

commit 75c6c844d9df37761e0e834df057b89e41816e55
Author:     Pedro Alves <palves@redhat.com>
AuthorDate: Fri Jan 10 20:05:54 2020 +0000
Commit:     Pedro Alves <palves@redhat.com>
CommitDate: Fri Jan 10 20:05:54 2020 +0000

    Fix reconnecting to a gdbserver already debugging multiple processes, II
    
    Another bug exposed by gdb.server/extended-remote-restart.exp in the
    multi-target work is that remote_target::start_remote can leave
    inferior_ptid and current_inferior() out of sync:
    
     (top-gdb) p current_inferior_->pid
     $1 = 29541
     (top-gdb) p inferior_ptid
     $2 = {m_pid = 29540, m_lwp = 29540, m_tid = 0}
    
    This is caused by writing to inferior_ptid directly instead of using
    switch_to_thread.  Also, "inferior_list->thread_list->ptid" assumes
    that we want the first thread of the first inferior, but that inferior
    may not have threads, or with multi-target, that target may be
    connected to some other target.
    
    gdb/ChangeLog:
    2020-01-10  Pedro Alves  <palves@redhat.com>
    
            * remote.c (remote_target::start_remote): Don't set inferior_ptid
            directly.  Instead find the first thread in the thread list and
            use switch_to_thread.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 4163c869af..a6fd8b11cd 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2020-01-10  Pedro Alves  <palves@redhat.com>
+
+	* remote.c (remote_target::start_remote): Don't set inferior_ptid
+	directly.  Instead find the first thread in the thread list and
+	use switch_to_thread.
+
 2020-01-10  Pedro Alves  <palves@redhat.com>
 
 	* remote.c (remote_target::remote_add_inferior): Don't bind a
diff --git a/gdb/remote.c b/gdb/remote.c
index 751769ea7f..f017f4a719 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -4701,8 +4701,8 @@ remote_target::start_remote (int from_tty, int extended_p)
 	     says should be current.  If we're reconnecting to a
 	     multi-threaded program, this will ideally be the thread
 	     that last reported an event before GDB disconnected.  */
-	  inferior_ptid = get_current_thread (wait_status);
-	  if (inferior_ptid == null_ptid)
+	  ptid_t curr_thread = get_current_thread (wait_status);
+	  if (curr_thread == null_ptid)
 	    {
 	      /* Odd... The target was able to list threads, but not
 		 tell us which thread was current (no "thread"
@@ -4714,8 +4714,14 @@ remote_target::start_remote (int from_tty, int extended_p)
 		                    "warning: couldn't determine remote "
 				    "current thread; picking first in list.\n");
 
-	      inferior_ptid = inferior_list->thread_list->ptid;
+	      for (thread_info *tp : all_non_exited_threads ())
+		{
+		  switch_to_thread (tp);
+		  break;
+		}
 	    }
+	  else
+	    switch_to_thread (find_thread_ptid (curr_thread));
 	}
 
       /* init_wait_for_inferior should be called before get_offsets in order