[binutils-gdb] [gdb/dap] Fix race between dap exit and gdb exit

[Tom de Vries <vries@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=706c6624c26b2c954713c872021594bd3a156dd3

commit 706c6624c26b2c954713c872021594bd3a156dd3
Author: Tom de Vries <tdevries@suse.de>
Date:   Thu Feb 22 11:35:26 2024 +0100

    [gdb/dap] Fix race between dap exit and gdb exit
    
    When DAP shuts down due to an EOF event, there's a race between:
    - gdb's main thread handling a SIGHUP, and
    - the DAP main thread exiting.
    
    Fix this by waiting for DAP's main thread exit during the gdb_exiting event.
    
    Tested on aarch64-linux.
    
    Approved-By: Tom Tromey <tom@tromey.com>
    
    PR dap/31380
    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31380

Diff:
---
 gdb/python/lib/gdb/dap/startup.py | 10 +++++++++-
 gdb/testsuite/gdb.dap/eof.exp     |  9 +++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/gdb/python/lib/gdb/dap/startup.py b/gdb/python/lib/gdb/dap/startup.py
index 29fe78ecd53..a2b68996dba 100644
--- a/gdb/python/lib/gdb/dap/startup.py
+++ b/gdb/python/lib/gdb/dap/startup.py
@@ -93,7 +93,15 @@ def start_dap(target):
         _dap_thread = threading.current_thread()
         target()
 
-    start_thread("DAP", really_start_dap)
+    # Note: unlike _dap_thread, dap_thread is a local variable.
+    dap_thread = start_thread("DAP", really_start_dap)
+
+    def _on_gdb_exiting(event):
+        thread_log("joining DAP thread ...")
+        dap_thread.join()
+        thread_log("joining DAP thread done")
+
+    gdb.events.gdb_exiting.connect(_on_gdb_exiting)
 
 
 def in_gdb_thread(func):
diff --git a/gdb/testsuite/gdb.dap/eof.exp b/gdb/testsuite/gdb.dap/eof.exp
index a84b1d21e04..05048f2762a 100644
--- a/gdb/testsuite/gdb.dap/eof.exp
+++ b/gdb/testsuite/gdb.dap/eof.exp
@@ -38,3 +38,12 @@ dap_check_log_file
 
 # Check that first log message is present.
 dap_check_log_file_re [string_to_regexp "starting DAP server"]
+
+# There should be one "READ:" for the initialize request, and at least one
+# "WROTE:" for the initialize response.
+dap_check_log_file_re "READ:"
+dap_check_log_file_re "WROTE:"
+
+# Check that all thread termination messages are there.
+dap_check_log_file_re "JSON writer: terminating"
+dap_check_log_file_re "DAP: terminating"