From ff24d3db60352d1ec4468b3fccb4f26f2d2e52f9 Mon Sep 17 00:00:00 2001
From: Mikhail Khadarenka <chodorenko@mail.ru>
Date: Thu, 28 May 2026 13:00:23 +0200
Subject: [PATCH] Avoid blocking IMAP pool cleanup on logout

The IMAP connection pool garbage collector used to call logout while scanning and mutating the shared cache. A slow or stuck IMAP server could therefore keep the cleanup path busy for a long time and delay access to pooled sessions.

Protect the connection cache with a small NSLock, remove expired entries from the pool while holding that lock, and perform the network logout work afterwards on a background thread. This keeps the cache unavailable only for the short bookkeeping phase instead of for the duration of every IMAP LOGOUT command.

Also guard the collector against non-connection placeholders already supported by cacheEntry:forURL:, and keep the debug pool count behind the same synchronization.
---
 sope-mime/NGImap4/NGImap4ConnectionManager.h |  3 +-
 sope-mime/NGImap4/NGImap4ConnectionManager.m | 86 +++++++++++++++++---
 2 files changed, 78 insertions(+), 11 deletions(-)

diff --git a/sope-mime/NGImap4/NGImap4ConnectionManager.h b/sope-mime/NGImap4/NGImap4ConnectionManager.h
index b5f65c1cd..df44614b5 100644
--- a/sope-mime/NGImap4/NGImap4ConnectionManager.h
+++ b/sope-mime/NGImap4/NGImap4ConnectionManager.h
@@ -30,12 +30,13 @@
   This class manages and pools NGImap4Connection objects.
 */
 
-@class NSString, NSTimer, NSMutableDictionary, NSURL;
+@class NSString, NSTimer, NSMutableDictionary, NSLock, NSURL;
 @class NGImap4Connection, NGImap4Client;
 
 @interface NGImap4ConnectionManager : NSObject
 {
   NSMutableDictionary *urlToEntry;
+  NSLock *entryLock;
   NSTimer *gcTimer;
 }
 
diff --git a/sope-mime/NGImap4/NGImap4ConnectionManager.m b/sope-mime/NGImap4/NGImap4ConnectionManager.m
index 2d361220e..1c8145a96 100644
--- a/sope-mime/NGImap4/NGImap4ConnectionManager.m
+++ b/sope-mime/NGImap4/NGImap4ConnectionManager.m
@@ -24,6 +24,10 @@
 #include "NGImap4Client.h"
 #include "imCommon.h"
 
+#import <Foundation/NSAutoreleasePool.h>
+#import <Foundation/NSLock.h>
+#import <Foundation/NSThread.h>
+
 @implementation NGImap4ConnectionManager
 
 static BOOL           debugOn    = NO;
@@ -79,6 +83,7 @@ - (id)init {
   if ((self = [super init])) {
     if (!poolingOff) {
       self->urlToEntry = [[NSMutableDictionary alloc] initWithCapacity:256];
+      self->entryLock = [[NSLock alloc] init];
       self->gcTimer = [[NSTimer scheduledTimerWithTimeInterval:
 				  PoolScanInterval
 				target:self selector:@selector(_garbageCollect:)
@@ -91,6 +96,7 @@ - (id)init {
 - (void)dealloc {
   [self->gcTimer invalidate];
   [self->urlToEntry release];
+  [self->entryLock  release];
   [self->gcTimer    release];
   [super dealloc];
 }
@@ -104,39 +110,99 @@ - (id)cacheKeyForURL:(NSURL *)_url {
 }
 
 - (NGImap4Connection *)entryForURL:(NSURL *)_url {
+  NGImap4Connection *entry;
+
   if (_url == nil)
     return nil;
-  
-  return [self->urlToEntry objectForKey:[self cacheKeyForURL:_url]];
+
+  [self->entryLock lock];
+  entry = [[self->urlToEntry objectForKey:[self cacheKeyForURL:_url]] retain];
+  [self->entryLock unlock];
+
+  return [entry autorelease];
 }
 - (void)cacheEntry:(NGImap4Connection *)_entry forURL:(NSURL *)_url {
   if (_entry == nil) _entry = (id)[NSNull null];
+  [self->entryLock lock];
   [self->urlToEntry setObject:_entry forKey:[self cacheKeyForURL:_url]];
+  [self->entryLock unlock];
+}
+
+- (unsigned int)poolEntryCount {
+  unsigned int count;
+
+  [self->entryLock lock];
+  count = [self->urlToEntry count];
+  [self->entryLock unlock];
+
+  return count;
+}
+
+- (void)_logoutClients:(NSArray *)_clients {
+  NSAutoreleasePool *pool;
+  NGImap4Client *client;
+  unsigned int i, count;
+
+  pool = [[NSAutoreleasePool alloc] init];
+  count = [_clients count];
+
+  for (i = 0; i < count; i++)
+    {
+      client = [_clients objectAtIndex:i];
+
+      NS_DURING
+        [client logout];
+      NS_HANDLER
+        [self logWithFormat:@"could not logout expired IMAP4 connection: %@",
+              localException];
+      NS_ENDHANDLER;
+    }
+
+  [_clients release];
+  [pool release];
 }
 
 - (void)_garbageCollect:(NSTimer *)_timer {
   // TODO: scan for old IMAP4 channels
   NGImap4Connection *entry;
+  NSMutableArray *clientsToLogout;
   NSDate *now;
   NSArray *a;
-  int i;
+  NSString *key;
+  NSArray *clients;
+  unsigned int i, count;
 
-  a = [self->urlToEntry allKeys];
+  clientsToLogout = [NSMutableArray arrayWithCapacity:16];
   now = [NSDate date];
 
-  for (i = 0; i < [a count]; i++)
+  [self->entryLock lock];
+  a = [self->urlToEntry allKeys];
+  count = [a count];
+
+  for (i = 0; i < count; i++)
     {
-      entry = [self->urlToEntry objectForKey: [a objectAtIndex: i]];
+      key = [a objectAtIndex: i];
+      entry = [self->urlToEntry objectForKey: key];
 
-      if ([now timeIntervalSinceDate: [entry creationTime]] > PoolScanInterval)
+      if ([entry isKindOfClass:[NGImap4Connection class]]
+          && [now timeIntervalSinceDate: [entry creationTime]] > PoolScanInterval)
 	{
-	  [[entry client] logout];
-	  [self->urlToEntry removeObjectForKey: [a objectAtIndex: i]];
+	  [clientsToLogout addObject: [entry client]];
+	  [self->urlToEntry removeObjectForKey: key];
 	}
     }
+  [self->entryLock unlock];
+
+  if ([clientsToLogout count] > 0)
+    {
+      clients = [clientsToLogout copy];
+      [NSThread detachNewThreadSelector:@selector(_logoutClients:)
+                toTarget:self
+                withObject:clients];
+    }
 
   [self debugWithFormat:@"should collect IMAP4 channels (%d active)",
-	  [self->urlToEntry count]];
+	  [self poolEntryCount]];
 }
 
 - (NGImap4Connection *)connectionForURL:(NSURL *)_url password:(NSString *)_p {