Apply remote-file-name-access-timeout in desktop.el and recentf.el

* doc/emacs/files.texi (File Conveniences):
* doc/emacs/misc.texi (Saving Emacs Sessions):
Mention remote-file-name-access-timeout.

* doc/misc/tramp.texi (Frequently Asked Questions): Add note.

* etc/NEWS: Explain use of 'remote-file-name-access-timeout' in
desktop.el and recentf.el.

* lisp/desktop.el (desktop-access-file): New defun.
(desktop-restore-file-buffer): Use it.

* lisp/recentf.el (recentf-access-file): New defun.
(recentf-keep-default-predicate): Use it.

* lisp/net/tramp.el (tramp-handle-access-file): Improve error handling.

doc/emacs/files.texi

@@ -2255,6 +2255,12 @@ to visit one of these files.  @kbd{M-x recentf-save-list} saves the
 current @code{recentf-list} to a file, and @kbd{M-x recentf-edit-list}
 edits it.
 
+@vindex remote-file-name-access-timeout
+  If you use remote files, you might also consider to customize
+@code{remote-file-name-access-timeout} to a proper value (number of
+seconds), after which time a check whether a remote file shall be used
+in Recentf is stopped.  This prevents Emacs to be blocked.
+
 @c FIXME partial-completion-mode (complete.el) is obsolete.
   The @kbd{M-x ffap} command generalizes @code{find-file} with more
 powerful heuristic defaults (@pxref{FFAP}), often based on the text at

doc/emacs/misc.texi

@@ -2812,9 +2812,13 @@ frame parameters you don't want to be restored; they will then be set
 according to your customizations in the init file.
 
 @vindex desktop-files-not-to-save
+@vindex remote-file-name-access-timeout
   Information about buffers visiting remote files is not saved by
 default.  Customize the variable @code{desktop-files-not-to-save} to
-change this.
+change this.  In this case, you might also consider to customize
+@code{remote-file-name-access-timeout} to a proper value (number of
+seconds), after which time a buffer restoration of a remote file is
+stopped.  This prevents Emacs to be blocked.
 
 @vindex desktop-restore-eager
   By default, all the buffers in the desktop are restored in one go.

doc/misc/tramp.texi

@@ -5181,6 +5181,11 @@ If the connection to the remote host isn't established yet, and if
 this requires an interactive password, the timeout check doesn't work
 properly.
 
+@c Since Emacs 30.
+@strong{Note}: In recent versions of Emacs, both packages apply
+already this check.  You just need to customize
+@code{remote-file-name-access-timeout}.
+
 
 @item
 Does @value{tramp} support @acronym{SSH} security keys?

etc/NEWS

@@ -454,6 +454,24 @@ which makes them visually distinct from subroutine prototypes.
 CPerl mode supports the new keywords for exception handling and the
 object oriented syntax which were added in Perl 5.36 and 5.38.
 
+** Emacs Sessions (Desktop)
+
++++
+*** Restoring buffers with remote files should not block.
+When a buffer is restored which uses a remote file, the user option
+'remote-file-name-access-timeout' could be set to a positive number.
+This value will be used as timeout (in seconds) for checking, whether
+the remote file is accessible.
+
+** Recentf
+
++++
+*** Checking recent remote files should not block.
+When a a remote file is checked in 'recentf-list', the user option
+'remote-file-name-access-timeout' could be set to a positive number.
+This value will be used as timeout (in seconds) for checking, whether
+the remote file is accessible.
+
 
 * New Modes and Packages in Emacs 30.1
 

lisp/desktop.el

@@ -1499,6 +1499,11 @@ This function is called from `window-configuration-change-hook'."
   (desktop-clear)
   (desktop-read desktop-dirname))
 
+;; ----------------------------------------------------------------------------
+(defun desktop-access-file (filename)
+  "Check whether FILENAME is accessible."
+  (ignore-errors (not (access-file filename "Restoring desktop buffer"))))
+
 (defvar desktop-buffer-major-mode)
 (defvar desktop-buffer-locals)
 (defvar auto-insert)  ; from autoinsert.el
@@ -1508,8 +1513,8 @@ This function is called from `window-configuration-change-hook'."
                                     _buffer-misc)
   "Restore a file buffer."
   (when buffer-filename
-    (if (or (file-exists-p buffer-filename)
-	    (let ((msg (format "Desktop: File \"%s\" no longer exists."
+    (if (or (desktop-access-file buffer-filename)
+	    (let ((msg (format "Desktop: File \"%s\" no longer accessible."
 			       buffer-filename)))
 	      (if desktop-missing-file-warning
 		  (y-or-n-p (concat msg " Re-create buffer? "))

lisp/net/tramp.el

@@ -3993,9 +3993,14 @@ Let-bind it when necessary.")
     (with-parsed-tramp-file-name filename v
       (with-tramp-timeout
 	  (timeout
+	   (unless (when-let ((p (tramp-get-connection-process v)))
+		     (and (process-live-p p)
+			  (tramp-get-connection-property p "connected")))
+	     (tramp-cleanup-connection v 'keep-debug 'keep-password))
 	   (tramp-error
 	    v 'file-error
-	    (format "%s: Timeout %s second(s) accessing %s" string timeout filename)))
+	    (format
+	     "%s: Timeout %s second(s) accessing %s" string timeout filename)))
 	(setq filename (file-truename filename))
 	(if (file-exists-p filename)
 	    (unless

lisp/recentf.el

@@ -112,11 +112,15 @@ must return non-nil to exclude it."
   :group 'recentf
   :type '(repeat (choice regexp function)))
 
+(defun recentf-access-file (filename)
+  "Check whether FILENAME is accessible."
+  (ignore-errors (not (access-file filename "Checking recentf file"))))
+
 (defun recentf-keep-default-predicate (file)
   "Return non-nil if FILE should be kept in the recent list.
 It handles the case of remote files as well."
   (cond
-   ((file-remote-p file nil t) (file-readable-p file))
+   ((file-remote-p file nil t) (recentf-access-file file))
    ((file-remote-p file))
    ((file-readable-p file))))