[balsa] Do not depend on undefined behavior of POSIX mutex

[Peter Bloomfield <PeterB src gnome org>]

commit 8dc9552e99b8ff4b3975cc0b10523963e5694282
Author: Peter Bloomfield <PeterBloomfield bellsouth net>
Date:   Fri Sep 9 19:49:34 2011 -0400

    Do not depend on undefined behavior of POSIX mutex
    
    	* src/main-window.c: use checking_mail_lock to protect access to
    	checking_mail.
    	* src/main.c (balsa_cleanup): ditto.
    	* src/threads.h: declare checking_mail.

 ChangeLog         |    7 +++++++
 src/main-window.c |   19 +++++++++++--------
 src/main.c        |    8 +++++---
 src/threads.h     |    1 +
 4 files changed, 24 insertions(+), 11 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index 0ea929a..f3455e5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2011-09-09  Peter Bloomfield  <peter t43 bellsouth net>
+
+	* src/main-window.c: use checking_mail_lock to protect access to
+	checking_mail.
+	* src/main.c (balsa_cleanup): ditto.
+	* src/threads.h: declare checking_mail.
+
 2011-09-01  Peter Bloomfield
 
 	* libbalsa/misc.c (lb_text_attr): add gssize len argument;
diff --git a/src/main-window.c b/src/main-window.c
index d01489f..3be6d7d 100644
--- a/src/main-window.c
+++ b/src/main-window.c
@@ -1914,12 +1914,7 @@ balsa_window_new()
 
 #ifdef BALSA_USE_THREADS
     /* set initial state of Get-New-Mail button */
-    if (pthread_mutex_trylock(&checking_mail_lock))
-        bw_set_sensitive(window, "GetNewMail", FALSE);
-    else {
-        bw_set_sensitive(window, "GetNewMail", TRUE);
-        pthread_mutex_unlock(&checking_mail_lock);
-    }
+    bw_set_sensitive(window, "GetNewMail", !checking_mail);
 #endif
 
     bw_set_visible(window, "MailboxTabMenu", FALSE);
@@ -2924,18 +2919,23 @@ check_new_messages_real(BalsaWindow * window, int type)
 #ifdef BALSA_USE_THREADS
     struct check_messages_thread_info *info;
     /*  Only Run once -- If already checking mail, return.  */
-    if (pthread_mutex_trylock(&checking_mail_lock)) {
+     pthread_mutex_lock(&checking_mail_lock);
+     if (checking_mail) {
+         pthread_mutex_unlock(&checking_mail_lock);
         fprintf(stderr, "Already Checking Mail!\n");
 	if (progress_dialog)
 	    gtk_window_present(GTK_WINDOW(progress_dialog));
         return;
     }
+    checking_mail = 1;
     if (window)
         bw_set_sensitive(window, "GetNewMail", FALSE);
 
     quiet_check = (type == TYPE_CALLBACK) 
         ? 0 : balsa_app.quiet_background_check;
 
+    pthread_mutex_unlock(&checking_mail_lock);
+
     if (type == TYPE_CALLBACK && 
         (balsa_app.pwindow_option == WHILERETR ||
          (balsa_app.pwindow_option == UNTILCLOSED && progress_dialog)))
@@ -3108,6 +3108,7 @@ bw_check_messages_thread(struct check_messages_thread_info *info)
     /*  
      *  It is assumed that this will always be called as a pthread,
      *  and that the calling procedure will check for an existing lock
+     *  and set checking_mail to true before calling.
      */
     MailThreadMessage *threadmessage;
     GSList *list = info->list;
@@ -3124,7 +3125,8 @@ bw_check_messages_thread(struct check_messages_thread_info *info)
     MSGMAILTHREAD(threadmessage, LIBBALSA_NTFY_FINISHED, NULL, "Finished",
                   0, 0);
     
-    pthread_mutex_unlock(&checking_mail_lock);
+    pthread_mutex_lock(&checking_mail_lock);
+    checking_mail = 0;
 
     if (info->window) {
         gdk_threads_enter();
@@ -3132,6 +3134,7 @@ bw_check_messages_thread(struct check_messages_thread_info *info)
         g_object_unref(info->window);
         gdk_threads_leave();
     }
+    pthread_mutex_unlock(&checking_mail_lock);
     
     g_free(info);
     pthread_exit(0);
diff --git a/src/main.c b/src/main.c
index 76897c4..9f4d53b 100644
--- a/src/main.c
+++ b/src/main.c
@@ -89,6 +89,7 @@
 pthread_t get_mail_thread;
 pthread_t send_mail;
 pthread_mutex_t send_messages_lock;
+int checking_mail;
 int mail_thread_pipes[2];
 int send_thread_pipes[2];
 GIOChannel *mail_thread_msg_send;
@@ -1200,7 +1201,8 @@ balsa_cleanup(void)
        There are actually many things to do, e.g. threads should not
        be started after this point.
     */
-    if (pthread_mutex_trylock(&checking_mail_lock)) {
+    pthread_mutex_lock(&checking_mail_lock);
+    if(checking_mail) {
         /* We want to quit but there is a checking thread active.
            The alternatives are to:
            a. wait for the checking thread to finish - but it could be
@@ -1210,8 +1212,8 @@ balsa_cleanup(void)
         pthread_cancel(get_mail_thread);
         printf("Mail check thread cancelled. I know it is rough.\n");
         sleep(1);
-    } else
-        pthread_mutex_unlock(&checking_mail_lock);
+    }
+    pthread_mutex_unlock(&checking_mail_lock);
 #endif
     balsa_app_destroy();
     g_hash_table_destroy(libbalsa_mailbox_view_table);
diff --git a/src/threads.h b/src/threads.h
index 1f60ac1..0de5c63 100644
--- a/src/threads.h
+++ b/src/threads.h
@@ -29,6 +29,7 @@ extern pthread_mutex_t checking_mail_lock;
 
 /*  define thread globals */
 extern pthread_t get_mail_thread;
+extern int checking_mail;
 extern int mail_thread_pipes[2];
 extern GIOChannel *mail_thread_msg_send;
 extern GIOChannel *mail_thread_msg_receive;