From 47ccd6b84bdf35688fb1516f06db68462bd24585 Mon Sep 17 00:00:00 2001
From: Tom Tromey <tom@tromey.com>
Date: Tue, 29 Mar 2022 14:36:10 -0600
Subject: [PATCH] Only allow QUIT on the main thread

Pedro pointed out that gdb worker threads should not react to quits.
While I don't think that the new DWARF reader can call QUIT from a
worker thread (and I don't think the existing minsym threading code
can either), it seems safest to address this before checking in the
new code.  This patch arranges for the QUIT macro to only work on the
main thread.
---
 gdb/run-on-main-thread.c | 20 ++++++++++++++++++++
 gdb/run-on-main-thread.h |  4 ++++
 gdb/utils.c              |  4 ++++
 3 files changed, 28 insertions(+)

diff --git a/gdb/run-on-main-thread.c b/gdb/run-on-main-thread.c
index ea633d9d2d0..eb22310f5c0 100644
--- a/gdb/run-on-main-thread.c
+++ b/gdb/run-on-main-thread.c
@@ -20,6 +20,7 @@
 #include "run-on-main-thread.h"
 #include "ser-event.h"
 #if CXX_STD_THREAD
+#include <thread>
 #include <mutex>
 #endif
 #include "gdbsupport/event-loop.h"
@@ -38,6 +39,10 @@ static std::vector<std::function<void ()>> runnables;
 
 static std::mutex runnable_mutex;
 
+/* The main thread.  */
+
+static std::thread::id main_thread;
+
 #endif
 
 /* Run all the queued runnables.  */
@@ -89,10 +94,25 @@ run_on_main_thread (std::function<void ()> &&func)
   serial_event_set (runnable_event);
 }
 
+/* See run-on-main-thread.h.  */
+
+bool
+is_main_thread ()
+{
+#if CXX_STD_THREAD
+  return std::this_thread::get_id () == main_thread;
+#else
+  return true;
+#endif
+}
+
 void _initialize_run_on_main_thread ();
 void
 _initialize_run_on_main_thread ()
 {
+#if CXX_STD_THREAD
+  main_thread = std::this_thread::get_id ();
+#endif
   runnable_event = make_serial_event ();
   add_file_handler (serial_event_fd (runnable_event), run_events, nullptr,
 		    "run-on-main-thread");
diff --git a/gdb/run-on-main-thread.h b/gdb/run-on-main-thread.h
index 0bfe0b7456a..888328e7a51 100644
--- a/gdb/run-on-main-thread.h
+++ b/gdb/run-on-main-thread.h
@@ -25,4 +25,8 @@
 
 extern void run_on_main_thread (std::function<void ()> &&);
 
+/* Return true on the main thread.  */
+
+extern bool is_main_thread ();
+
 #endif /* GDB_RUN_ON_MAIN_THREAD_H */
diff --git a/gdb/utils.c b/gdb/utils.c
index 2df9b1d7dcf..9ca268ad07f 100644
--- a/gdb/utils.c
+++ b/gdb/utils.c
@@ -78,6 +78,7 @@
 #include "bt-utils.h"
 #include "gdbsupport/buildargv.h"
 #include "pager.h"
+#include "run-on-main-thread.h"
 
 void (*deprecated_error_begin_hook) (void);
 
@@ -681,6 +682,9 @@ quit (void)
 void
 maybe_quit (void)
 {
+  if (!is_main_thread ())
+    return;
+
   if (sync_quit_force_run)
     quit ();
 
-- 
2.30.2