From f4e552f9829743f5dfa8661112b6f703f011215b Mon Sep 17 00:00:00 2001
From: Jesse Duffield <jessedduffield@gmail.com>
Date: Tue, 6 Apr 2021 13:32:55 +1000
Subject: [PATCH] prevent deadlocks.

Hard to choose between the lock with a defer unlock in an anonymous function
vs just having an explicit unlock at the end with additional unlocks before
any early returns. The former is less error prone, but the former is much more
readable, especially if the anonymous function would have needed to return
an error value.
---
 pkg/gui/context.go | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/pkg/gui/context.go b/pkg/gui/context.go
index 7b5ac5cdc..a06fae4a7 100644
--- a/pkg/gui/context.go
+++ b/pkg/gui/context.go
@@ -395,9 +395,6 @@ func (gui *Gui) replaceContext(c Context) error {
 
 func (gui *Gui) pushContext(c Context) error {
 	gui.g.Update(func(*gocui.Gui) error {
-		gui.State.ContextManager.Lock()
-		defer gui.State.ContextManager.Unlock()
-
 		return gui.pushContextDirect(c)
 	})
 
@@ -405,12 +402,15 @@ func (gui *Gui) pushContext(c Context) error {
 }
 
 func (gui *Gui) pushContextDirect(c Context) error {
+	gui.State.ContextManager.Lock()
+
 	// push onto stack
 	// if we are switching to a side context, remove all other contexts in the stack
 	if c.GetKind() == SIDE_CONTEXT {
 		for _, stackContext := range gui.State.ContextManager.ContextStack {
 			if stackContext.GetKey() != c.GetKey() {
 				if err := gui.deactivateContext(stackContext); err != nil {
+					gui.State.ContextManager.Unlock()
 					return err
 				}
 			}
@@ -424,6 +424,8 @@ func (gui *Gui) pushContextDirect(c Context) error {
 		gui.State.ContextManager.ContextStack = append(gui.State.ContextManager.ContextStack, c)
 	}
 
+	gui.State.ContextManager.Unlock()
+
 	return gui.activateContext(c)
 }
 
@@ -439,10 +441,10 @@ func (gui *Gui) pushContextWithView(viewName string) error {
 func (gui *Gui) returnFromContext() error {
 	gui.g.Update(func(*gocui.Gui) error {
 		gui.State.ContextManager.Lock()
-		defer gui.State.ContextManager.Unlock()
 
 		if len(gui.State.ContextManager.ContextStack) == 1 {
 			// cannot escape from bottommost context
+			gui.State.ContextManager.Unlock()
 			return nil
 		}
 
@@ -453,6 +455,8 @@ func (gui *Gui) returnFromContext() error {
 
 		gui.State.ContextManager.ContextStack = gui.State.ContextManager.ContextStack[:n]
 
+		gui.State.ContextManager.Unlock()
+
 		if err := gui.deactivateContext(currentContext); err != nil {
 			return err
 		}
@@ -513,10 +517,8 @@ func (gui *Gui) postRefreshUpdate(c Context) error {
 func (gui *Gui) activateContext(c Context) error {
 	viewName := c.GetViewName()
 	v, err := gui.g.View(viewName)
-	// if view no longer exists, pop again
-	// (note: this should never happen, unless we call this code before our views are initialised)
 	if err != nil {
-		return gui.returnFromContext()
+		return err
 	}
 	originalViewContextKey := ContextKey(v.Context)
 
@@ -532,8 +534,7 @@ func (gui *Gui) activateContext(c Context) error {
 	gui.setViewTabForContext(c)
 
 	if _, err := gui.g.SetCurrentView(viewName); err != nil {
-		// if view no longer exists, pop again
-		return gui.returnFromContext()
+		return err
 	}
 
 	v.Visible = true