From a1dc119bfb777f813f7967256fc0835c34d2c0be Mon Sep 17 00:00:00 2001
From: Manuel Giraud <manuel@ledu-giraud.fr>
Date: Thu, 3 Feb 2022 13:52:41 +0100
Subject: [PATCH 3/4] mutex on nnmail cache.

---
 lisp/gnus/nnmail.el | 83 ++++++++++++++++++++++++---------------------
 1 file changed, 44 insertions(+), 39 deletions(-)

diff --git a/lisp/gnus/nnmail.el b/lisp/gnus/nnmail.el
index af9c439280..642ca16e28 100644
--- a/lisp/gnus/nnmail.el
+++ b/lisp/gnus/nnmail.el
@@ -1556,6 +1556,7 @@ nnmail-message-id
 ;;;
 
 (defvar nnmail-cache-buffer nil)
+(defvar nnmail-cache-buffer-mutex (make-mutex))
 
 (defun nnmail-cache-open ()
   (if (or (not nnmail-treat-duplicates)
@@ -1574,22 +1575,23 @@ nnmail-cache-close
   (when (and nnmail-treat-duplicates
              (buffer-live-p nnmail-cache-buffer)
 	     (buffer-modified-p nnmail-cache-buffer))
-    (with-current-buffer nnmail-cache-buffer
-      ;; Weed out the excess number of Message-IDs.
-      (goto-char (point-max))
-      (when (search-backward "\n" nil t nnmail-message-id-cache-length)
-	(progn
-	  (beginning-of-line)
-	  (delete-region (point-min) (point))))
-      ;; Save the buffer.
-      (or (file-exists-p (file-name-directory nnmail-message-id-cache-file))
-	  (make-directory (file-name-directory nnmail-message-id-cache-file)
-			  t))
-      (nnmail-write-region (point-min) (point-max)
-			   nnmail-message-id-cache-file nil 'silent)
-      (set-buffer-modified-p nil)
-      (setq nnmail-cache-buffer nil)
-      (gnus-kill-buffer (current-buffer)))))
+    (with-mutex nnmail-cache-buffer-mutex
+      (with-current-buffer nnmail-cache-buffer
+        ;; Weed out the excess number of Message-IDs.
+        (goto-char (point-max))
+        (when (search-backward "\n" nil t nnmail-message-id-cache-length)
+	  (progn
+	    (beginning-of-line)
+	    (delete-region (point-min) (point))))
+        ;; Save the buffer.
+        (or (file-exists-p (file-name-directory nnmail-message-id-cache-file))
+	    (make-directory (file-name-directory nnmail-message-id-cache-file)
+			    t))
+        (nnmail-write-region (point-min) (point-max)
+			     nnmail-message-id-cache-file nil 'silent)
+        (set-buffer-modified-p nil)
+        (setq nnmail-cache-buffer nil)
+        (gnus-kill-buffer (current-buffer))))))
 
 (defun nnmail-cache-insert (id grp &optional subject sender)
   (when (stringp id)
@@ -1605,18 +1607,19 @@ nnmail-cache-insert
       ;; pass the first (of possibly >1) group which matches. -Josh
       (unless (gnus-buffer-live-p nnmail-cache-buffer)
 	(nnmail-cache-open))
-      (with-current-buffer nnmail-cache-buffer
-	(goto-char (point-max))
-	(if (and grp (not (string= "" grp))
-		 (gnus-methods-equal-p gnus-command-method
-				       (nnmail-cache-primary-mail-backend)))
-	    (let ((regexp (if (consp nnmail-cache-ignore-groups)
-			      (mapconcat #'identity nnmail-cache-ignore-groups
-					 "\\|")
-			    nnmail-cache-ignore-groups)))
-	      (unless (and regexp (string-match regexp grp))
-		(insert id "\t" grp "\n")))
-	  (insert id "\n"))))))
+      (with-mutex nnmail-cache-buffer-mutex
+        (with-current-buffer nnmail-cache-buffer
+	  (goto-char (point-max))
+	  (if (and grp (not (string= "" grp))
+		   (gnus-methods-equal-p gnus-command-method
+				         (nnmail-cache-primary-mail-backend)))
+	      (let ((regexp (if (consp nnmail-cache-ignore-groups)
+			        (mapconcat #'identity nnmail-cache-ignore-groups
+					   "\\|")
+			      nnmail-cache-ignore-groups)))
+	        (unless (and regexp (string-match regexp grp))
+		  (insert id "\t" grp "\n")))
+	    (insert id "\n")))))))
 
 (defun nnmail-cache-primary-mail-backend ()
   (let ((be-list (cons gnus-select-method gnus-secondary-select-methods))
@@ -1638,14 +1641,15 @@ nnmail-cache-primary-mail-backend
 ;; cache.
 (defun nnmail-cache-fetch-group (id)
   (when (and nnmail-treat-duplicates nnmail-cache-buffer)
-    (with-current-buffer nnmail-cache-buffer
-      (goto-char (point-max))
-      (when (search-backward id nil t)
-	(beginning-of-line)
-	(skip-chars-forward "^\n\r\t")
-	(unless (looking-at "[\r\n]")
-	  (forward-char 1)
-	  (buffer-substring (point) (point-at-eol)))))))
+    (with-mutex nnmail-cache-buffer-mutex
+      (with-current-buffer nnmail-cache-buffer
+        (goto-char (point-max))
+        (when (search-backward id nil t)
+	  (beginning-of-line)
+	  (skip-chars-forward "^\n\r\t")
+	  (unless (looking-at "[\r\n]")
+	    (forward-char 1)
+	    (buffer-substring (point) (point-at-eol))))))))
 
 ;; Function for nnmail-split-fancy: look up all references in the
 ;; cache and if a match is found, return that group.
@@ -1682,9 +1686,10 @@ nnmail-split-fancy-with-parent
 
 (defun nnmail-cache-id-exists-p (id)
   (when nnmail-treat-duplicates
-    (with-current-buffer nnmail-cache-buffer
-      (goto-char (point-max))
-      (search-backward id nil t))))
+    (with-mutex nnmail-cache-buffer-mutex
+      (with-current-buffer nnmail-cache-buffer
+        (goto-char (point-max))
+        (search-backward id nil t)))))
 
 (defun nnmail-fetch-field (header)
   (save-excursion
-- 
2.35.1