Subject: Re: bug#79367: 31.0.50; magit-commit sometimes doesn't work if diff-hl-update-async is t

From: Eli Zaretskii <[email-masked]>
Date: Wed, 03 Sep 2025 17:13:42 +0300

> Cc: [email-masked], [email-masked], [email-masked]
> Date: Wed, 03 Sep 2025 14:25:58 +0300
> From: Eli Zaretskii <[email-masked]>
> 
> > >   . if the process on behalf of which we called
> > >     server_accept_connection was not locked to some thread, undo what
> > >     make_process did to the new process when it called pset_thread
> > >   . otherwise, call set_proc_thread to lock the new process to the
> > >     same thread as the one which caused this call
> > 
> > Whatever you do, please post your change for review rather than just
> > pushing it.
> 
> Will do.

The proposed patch is below.

Zhengyi Fu, can you please apply it to the current master, and see if
it solves the original problem?

diff --git a/src/process.c b/src/process.c
index d6efac5..0c41ec6 100644
--- a/src/process.c
+++ b/src/process.c
@@ -5078,6 +5078,10 @@ server_accept_connection (Lisp_Object server, int channel)
   fcntl (s, F_SETFL, O_NONBLOCK);
 
   p = XPROCESS (proc);
+  /* make_process calls pset_thread, but if the server process is not
+     locked to any thread, we need to undo what make_process did.  */
+  if (NILP (ps->thread))
+    pset_thread (p, Qnil);
 
   /* Build new contact information for this setup.  */
   contact = Fcopy_sequence (ps->childp);
@@ -5117,6 +5121,13 @@ server_accept_connection (Lisp_Object server, int channel)
     add_process_read_fd (s);
   if (s > max_desc)
     max_desc = s;
+  /* If the server process is locked to this thread, lock the client
+     process to the same thread.  */
+  if (!NILP (ps->thread))
+    {
+      eassert (XTHREAD (ps->thread) == current_thread);
+      set_proc_thread (p, XTHREAD (ps->thread));
+    }
 
   /* Setup coding system for new process based on server process.
      This seems to be the proper thing to do, as the coding system