From eb1c272ab5230d548077b9f59aca4b3457c3a8f8 Mon Sep 17 00:00:00 2001
From: GaryOderNichts <garyodernichts@gmail.com>
Date: Sat, 17 Dec 2022 16:28:40 +0100
Subject: [PATCH] Fix a9e845 and 797755 Allow X*IfEvent() to reenter libX11

---
 include/X11/Xlibint.h |  9 +++++-
 src/ChkIfEv.c         |  5 +++-
 src/IfEvent.c         |  5 +++-
 src/PeekIfEv.c        |  5 +++-
 src/locking.c         | 65 +++++++++----------------------------------
 5 files changed, 33 insertions(+), 56 deletions(-)

diff --git a/include/X11/Xlibint.h b/include/X11/Xlibint.h
index e20c4833..50099b43 100644
--- a/include/X11/Xlibint.h
+++ b/include/X11/Xlibint.h
@@ -43,6 +43,10 @@ from The Open Group.
 #include <X11/Xproto.h>		/* to declare xEvent */
 #include <X11/XlibConf.h>	/* for configured options like XTHREADS */
 
+#ifdef XTHREADS
+#include <X11/Xthreads.h>
+#endif
+
 /* The Xlib structs are full of implicit padding to properly align members.
    We can't clean that up without breaking ABI, so tell clang not to bother
    complaining about it. */
@@ -207,7 +211,10 @@ struct _XDisplay
 
 	XIOErrorExitHandler exit_handler;
 	void *exit_handler_data;
-        CARD32 in_ifevent;
+	CARD32 in_ifevent;
+#ifdef XTHREADS
+	xthread_t ifevent_thread;
+#endif
 };
 
 #define XAllocIDs(dpy,ids,n) (*(dpy)->idlist_alloc)(dpy,ids,n)
diff --git a/src/ChkIfEv.c b/src/ChkIfEv.c
index b32c2d3e..66636696 100644
--- a/src/ChkIfEv.c
+++ b/src/ChkIfEv.c
@@ -49,8 +49,11 @@ Bool XCheckIfEvent (
 	unsigned long qe_serial = 0;
 	int n;			/* time through count */
 
-	dpy->in_ifevent++;
 	LockDisplay(dpy);
+#ifdef XTHREADS
+	dpy->ifevent_thread = xthread_self();
+#endif
+	dpy->in_ifevent++;
 	prev = NULL;
 	for (n = 3; --n >= 0;) {
 	    for (qelt = prev ? prev->next : dpy->head;
diff --git a/src/IfEvent.c b/src/IfEvent.c
index 54c37f00..35c592e3 100644
--- a/src/IfEvent.c
+++ b/src/IfEvent.c
@@ -48,8 +48,11 @@ XIfEvent (
 	register _XQEvent *qelt, *prev;
 	unsigned long qe_serial = 0;
 
-	dpy->in_ifevent++;
 	LockDisplay(dpy);
+#ifdef XTHREADS
+	dpy->ifevent_thread = xthread_self();
+#endif
+	dpy->in_ifevent++;
 	prev = NULL;
 	while (1) {
 	    for (qelt = prev ? prev->next : dpy->head;
diff --git a/src/PeekIfEv.c b/src/PeekIfEv.c
index 68c028b7..754749a7 100644
--- a/src/PeekIfEv.c
+++ b/src/PeekIfEv.c
@@ -49,8 +49,11 @@ XPeekIfEvent (
 	register _XQEvent *prev, *qelt;
 	unsigned long qe_serial = 0;
 
-	dpy->in_ifevent++;
 	LockDisplay(dpy);
+#ifdef XTHREADS
+	dpy->ifevent_thread = xthread_self();
+#endif
+	dpy->in_ifevent++;
 	prev = NULL;
 	while (1) {
 	    for (qelt = prev ? prev->next : dpy->head;
diff --git a/src/locking.c b/src/locking.c
index c550603e..3625bd27 100644
--- a/src/locking.c
+++ b/src/locking.c
@@ -240,7 +240,9 @@ static void _XUnlockDisplay(
     if (lock_hist_loc >= LOCK_HIST_SIZE)
 	lock_hist_loc = 0;
 #endif /* XTHREADS_WARN */
-    xmutex_unlock(dpy->lock->mutex);
+
+    if (dpy->in_ifevent == 0 || !xthread_equal(dpy->ifevent_thread, xthread_self()))
+        xmutex_unlock(dpy->lock->mutex);
 }
 
 
@@ -453,63 +455,24 @@ static void _XDisplayLockWait(
 }
 
 static void _XLockDisplay(
-    Display *dpy
-    XTHREADS_FILE_LINE_ARGS
-    );
-
-static void _XIfEventLockDisplay(
     Display *dpy
     XTHREADS_FILE_LINE_ARGS
     )
 {
-    /* assert(dpy->in_ifevent); */
-}
+    struct _XErrorThreadInfo *ti;
 
-static void _XInternalLockDisplay(
-    Display *dpy,
-    Bool wskip
-    XTHREADS_FILE_LINE_ARGS
-    );
+    if (dpy->in_ifevent && xthread_equal(dpy->ifevent_thread, xthread_self()))
+        return;
 
-static void _XIfEventInternalLockDisplay(
-    Display *dpy,
-    Bool wskip
-    XTHREADS_FILE_LINE_ARGS
-    )
-{
-    /* assert(dpy->in_ifevent); */
-}
-
-static void _XIfEventUnlockDisplay(
-    Display *dpy
-    XTHREADS_FILE_LINE_ARGS
-    )
-{
-    if (dpy->in_ifevent == 0) {
-	dpy->lock_fns->lock_display = _XLockDisplay;
-	dpy->lock_fns->unlock_display = _XUnlockDisplay;
-	dpy->lock->internal_lock_display = _XInternalLockDisplay;
-	UnlockDisplay(dpy);
-    } else
-	return;
-}
-
-static void _XLockDisplay(
-    Display *dpy
-    XTHREADS_FILE_LINE_ARGS
-    )
-{
-#ifdef XTHREADS
-    struct _XErrorThreadInfo *ti;
-#endif
 #ifdef XTHREADS_WARN
     _XLockDisplayWarn(dpy, file, line);
 #else
     xmutex_lock(dpy->lock->mutex);
 #endif
+
     if (dpy->lock->locking_level > 0)
-	_XDisplayLockWait(dpy);
-#ifdef XTHREADS
+    _XDisplayLockWait(dpy);
+
     /*
      * Skip the two function calls below which may generate requests
      * when LockDisplay is called from within _XError.
@@ -517,14 +480,9 @@ static void _XLockDisplay(
     for (ti = dpy->error_threads; ti; ti = ti->next)
 	    if (ti->error_thread == xthread_self())
 		    return;
-#endif
+
     _XIDHandler(dpy);
     _XSeqSyncFunction(dpy);
-    if (dpy->in_ifevent) {
-	dpy->lock_fns->lock_display = _XIfEventLockDisplay;
-	dpy->lock_fns->unlock_display = _XIfEventUnlockDisplay;
-	dpy->lock->internal_lock_display = _XIfEventInternalLockDisplay;
-    }
 }
 
 /*
@@ -537,6 +495,9 @@ static void _XInternalLockDisplay(
     XTHREADS_FILE_LINE_ARGS
     )
 {
+    if (dpy->in_ifevent && xthread_equal(dpy->ifevent_thread, xthread_self()))
+        return;
+
 #ifdef XTHREADS_WARN
     _XLockDisplayWarn(dpy, file, line);
 #else
-- 
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