[PATCH v2 17/24] Fix reconnecting to a gdbserver already debugging multiple processes, II

Pedro Alves
2019-10-17T22:50:46Z

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:
yyyy-mm-dd 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.
---
gdb/remote.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/gdb/remote.c b/gdb/remote.c
index bc1054b192..ae8720a5f4 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -4707,8 +4707,8 @@ 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"
@@ -4720,8 +4720,14 @@ 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
--
2.14.5