Release screen mutex if thread dies

We did not setup a thread cleanup procedure which resulted in calcurse
freezing if a thread tried to draw on the screen after another thread
was canceled while locking the screen.

Note that this kind of cleanup handlers should be added to other mutexes
as well. This patch just removes the most common case of triggering a
deadlock.

Also note that we cannot move pthread_cleanup_push() and
pthread_cleanup_pop() into the locking/unlocking functions since both
pthread_cleanup_push() and pthread_cleanup_pop() may be implemented as
macros that must be used in pairs within the same lexical scope.

Signed-off-by: Lukas Fleischer <calcurse@cryptocrack.de>

4 files changed, 72 insertions, 32 deletions

diff --git a/src/calcurse.h b/src/calcurse.h
index 7a7f4f2..d7b5093 100644
--- a/src/calcurse.h
+++ b/src/calcurse.h
@@ -456,6 +456,22 @@ enum win {
 #define FLAG_STA (1 << STA)
 #define FLAG_ALL ((1 << NBWINS) - 1)
 
+#define WINS_NBAR_LOCK \
+  pthread_cleanup_push(wins_nbar_cleanup, NULL); \
+  wins_nbar_lock();
+
+#define WINS_NBAR_UNLOCK \
+  wins_nbar_unlock(); \
+  pthread_cleanup_pop(0);
+
+#define WINS_CALENDAR_LOCK \
+  pthread_cleanup_push(wins_calendar_cleanup, NULL); \
+  wins_calendar_lock();
+
+#define WINS_CALENDAR_UNLOCK \
+  wins_calendar_unlock(); \
+  pthread_cleanup_pop(0);
+
 enum ui_mode {
   UI_CURSES,
   UI_CMDLINE,
@@ -977,8 +993,10 @@ void vars_init(void);
 extern struct window win[NBWINS];
 unsigned wins_nbar_lock(void);
 void wins_nbar_unlock(void);
+void wins_nbar_cleanup(void *);
 unsigned wins_calendar_lock(void);
 void wins_calendar_unlock(void);
+void wins_calendar_cleanup(void *);
 int wins_refresh(void);
 int wins_wrefresh(WINDOW *);
 int wins_doupdate(void);
diff --git a/src/calendar.c b/src/calendar.c
index 42ee449..df247df 100644
--- a/src/calendar.c
+++ b/src/calendar.c
@@ -297,7 +297,7 @@ draw_monthly_view(struct window *cwin, struct date *current_day,
   c_day_1 = (int)((ymd_to_scalar(yr, mo, 1 + sunday_first) - (long)1) % 7L);
 
   /* Write the current month and year on top of the calendar */
-  wins_calendar_lock();
+  WINS_CALENDAR_LOCK;
   custom_apply_attr(cwin->p, ATTR_HIGHEST);
   mvwprintw(cwin->p, ofs_y,
             (SBAR_WIDTH - (strlen(_(monthnames[mo - 1])) + 5)) / 2,
@@ -311,7 +311,7 @@ draw_monthly_view(struct window *cwin, struct date *current_day,
     mvwaddstr(cwin->p, ofs_y, ofs_x + 4 * j, _(daynames[1 + j - sunday_first]));
   }
   custom_remove_attr(cwin->p, ATTR_HIGHEST);
-  wins_calendar_unlock();
+  WINS_CALENDAR_UNLOCK;
 
   day_1_sav = (c_day_1 + 1) * 3 + c_day_1 - 7;
 
@@ -329,7 +329,7 @@ draw_monthly_view(struct window *cwin, struct date *current_day,
       ofs_x = OFFX - day_1_sav - 4 * c_day;
     }
 
-    wins_calendar_lock();
+    WINS_CALENDAR_LOCK;
     if (c_day == current_day->dd
         && current_day->mm == slctd_day.mm
         && current_day->yyyy == slctd_day.yyyy
@@ -355,7 +355,7 @@ draw_monthly_view(struct window *cwin, struct date *current_day,
       mvwprintw(cwin->p, ofs_y + 1,
                 ofs_x + day_1_sav + 4 * c_day + 1, "%2d", c_day);
     }
-    wins_calendar_unlock();
+    WINS_CALENDAR_UNLOCK;
   }
 }
 
@@ -459,11 +459,11 @@ draw_weekly_view(struct window *cwin, struct date *current_day,
 
   /* Print the week number. */
   weeknum = ISO8601weeknum(&t);
-  wins_calendar_lock();
+  WINS_CALENDAR_LOCK;
   custom_apply_attr(cwin->p, ATTR_HIGHEST);
   mvwprintw(cwin->p, 2, cwin->w - 9, "(# %02d)", weeknum);
   custom_remove_attr(cwin->p, ATTR_HIGHEST);
-  wins_calendar_unlock();
+  WINS_CALENDAR_UNLOCK;
 
   /* Now draw calendar view. */
   for (j = 0; j < WEEKINDAYS; j++) {
@@ -495,28 +495,28 @@ draw_weekly_view(struct window *cwin, struct date *current_day,
     else
       attr = 0;
 
-    wins_calendar_lock();
+    WINS_CALENDAR_LOCK;
     if (attr)
       custom_apply_attr(cwin->p, attr);
     mvwprintw(cwin->p, OFFY + 1, OFFX + 1 + 4 * j, "%02d", t.tm_mday);
     if (attr)
       custom_remove_attr(cwin->p, attr);
-    wins_calendar_unlock();
+    WINS_CALENDAR_UNLOCK;
 
     /* Draw slices indicating appointment times. */
     memset(slices, 0, DAYSLICESNO * sizeof *slices);
     if (day_chk_busy_slices(date, DAYSLICESNO, slices)) {
       for (i = 0; i < DAYSLICESNO; i++) {
         if (j != WEEKINDAYS - 1 && i != DAYSLICESNO - 1) {
-          wins_calendar_lock();
+          WINS_CALENDAR_LOCK;
           mvwhline(cwin->p, OFFY + 2 + i, OFFX + 3 + 4 * j, ACS_S9, 2);
-          wins_calendar_unlock();
+          WINS_CALENDAR_UNLOCK;
         }
         if (slices[i]) {
           int highlight;
 
           highlight = (t.tm_mday == slctd_day.dd) ? 1 : 0;
-          wins_calendar_lock();
+          WINS_CALENDAR_LOCK;
           if (highlight)
             custom_apply_attr(cwin->p, attr);
           wattron(cwin->p, A_REVERSE);
@@ -525,7 +525,7 @@ draw_weekly_view(struct window *cwin, struct date *current_day,
           wattroff(cwin->p, A_REVERSE);
           if (highlight)
             custom_remove_attr(cwin->p, attr);
-          wins_calendar_unlock();
+          WINS_CALENDAR_UNLOCK;
         }
       }
     }
@@ -535,13 +535,13 @@ draw_weekly_view(struct window *cwin, struct date *current_day,
   }
 
   /* Draw marks to indicate midday on the sides of the calendar. */
-  wins_calendar_lock();
+  WINS_CALENDAR_LOCK;
   custom_apply_attr(cwin->p, ATTR_HIGHEST);
   mvwhline(cwin->p, OFFY + 1 + DAYSLICESNO / 2, OFFX, ACS_S9, 1);
   mvwhline(cwin->p, OFFY + 1 + DAYSLICESNO / 2,
            OFFX + WCALWIDTH - 3, ACS_S9, 1);
   custom_remove_attr(cwin->p, ATTR_HIGHEST);
-  wins_calendar_unlock();
+  WINS_CALENDAR_UNLOCK;
 
 #undef DAYSLICESNO
 }
@@ -554,10 +554,10 @@ void calendar_update_panel(struct window *cwin)
 
   calendar_store_current_date(&current_day);
 
-  wins_calendar_lock();
+  WINS_CALENDAR_LOCK;
   erase_window_part(cwin->p, 1, 3, cwin->w - 2, cwin->h - 2);
   mvwhline(cwin->p, 2, 1, ACS_HLINE, cwin->w - 2);
-  wins_calendar_unlock();
+  WINS_CALENDAR_UNLOCK;
 
   sunday_first = calendar_week_begins_on_monday()? 0 : 1;
 
diff --git a/src/notify.c b/src/notify.c
index 6ac94b9..ebc9728 100644
--- a/src/notify.c
+++ b/src/notify.c
@@ -240,13 +240,13 @@ void notify_update_bar(void)
   app_pos = file_pos + strlen(notify.apts_file) + 2 + space;
   txt_max_len = col - (app_pos + 12 + space);
 
-  wins_nbar_lock();
+  WINS_NBAR_LOCK;
   custom_apply_attr(notify.win, ATTR_HIGHEST);
   wattron(notify.win, A_UNDERLINE | A_REVERSE);
   mvwhline(notify.win, 0, 0, ACS_HLINE, col);
   mvwprintw(notify.win, 0, date_pos, "[ %s | %s ]", notify.date, notify.time);
   mvwprintw(notify.win, 0, file_pos, "(%s)", notify.apts_file);
-  wins_nbar_unlock();
+  WINS_NBAR_UNLOCK;
 
   pthread_mutex_lock(&notify_app.mutex);
   if (notify_app.got_app) {
@@ -273,7 +273,7 @@ void notify_update_bar(void)
       else
         blinking = 0;
 
-      wins_nbar_lock();
+      WINS_NBAR_LOCK;
       if (blinking)
         wattron(notify.win, A_BLINK);
       if (too_long)
@@ -284,7 +284,7 @@ void notify_update_bar(void)
                   hours_left, minutes_left, notify_app.txt);
       if (blinking)
         wattroff(notify.win, A_BLINK);
-      wins_nbar_unlock();
+      WINS_NBAR_UNLOCK;
 
       if (blinking)
         notify_launch_cmd();
@@ -299,10 +299,10 @@ void notify_update_bar(void)
   }
   pthread_mutex_unlock(&notify_app.mutex);
 
-  wins_nbar_lock();
+  WINS_NBAR_LOCK;
   wattroff(notify.win, A_UNDERLINE | A_REVERSE);
   custom_remove_attr(notify.win, ATTR_HIGHEST);
-  wins_nbar_unlock();
+  WINS_NBAR_UNLOCK;
   wins_wrefresh(notify.win);
 
   pthread_mutex_unlock(&notify.mutex);
diff --git a/src/wins.c b/src/wins.c
index 64dd962..249610c 100644
--- a/src/wins.c
+++ b/src/wins.c
@@ -40,6 +40,14 @@
 
 #include "calcurse.h"
 
+#define SCREEN_ACQUIRE \
+  pthread_cleanup_push(screen_cleanup, (void *)NULL); \
+  screen_acquire();
+
+#define SCREEN_RELEASE \
+  screen_release(); \
+  pthread_cleanup_pop(0);
+
 /* Variables to handle calcurse windows. */
 struct window win[NBWINS];
 
@@ -76,6 +84,11 @@ static void screen_release(void)
   pthread_mutex_unlock(&screen_mutex);
 }
 
+static void screen_cleanup(void *arg)
+{
+  screen_release();
+}
+
 /*
  * FIXME: The following functions currently lock the whole screen. Use both
  * window-level and screen-level mutexes (or use use_screen() and use_window(),
@@ -92,6 +105,11 @@ void wins_nbar_unlock(void)
   screen_release();
 }
 
+void wins_nbar_cleanup(void *arg)
+{
+  wins_nbar_unlock();
+}
+
 unsigned wins_calendar_lock(void)
 {
   return screen_acquire();
@@ -102,14 +120,18 @@ void wins_calendar_unlock(void)
   screen_release();
 }
 
+void wins_calendar_cleanup(void *arg)
+{
+  wins_calendar_unlock();
+}
+
 int wins_refresh(void)
 {
   int rc;
 
-  if (!screen_acquire())
-    return ERR;
+  SCREEN_ACQUIRE;
   rc = refresh();
-  screen_release();
+  SCREEN_RELEASE;
 
   return rc;
 }
@@ -118,10 +140,11 @@ int wins_wrefresh(WINDOW * win)
 {
   int rc;
 
-  if (!win || !screen_acquire())
+  if (!win)
     return ERR;
+  SCREEN_ACQUIRE;
   rc = wrefresh(win);
-  screen_release();
+  SCREEN_RELEASE;
 
   return rc;
 }
@@ -130,10 +153,9 @@ int wins_doupdate(void)
 {
   int rc;
 
-  if (!screen_acquire())
-    return ERR;
+  SCREEN_ACQUIRE;
   rc = doupdate();
-  screen_release();
+  SCREEN_RELEASE;
 
   return rc;
 }
@@ -502,12 +524,12 @@ static void border_nocolor(WINDOW * window)
 void wins_update_border(int flags)
 {
   if (flags & FLAG_CAL) {
-    wins_calendar_lock();
+    WINS_CALENDAR_LOCK;
     if (slctd_win == CAL)
       border_color(win[CAL].p);
     else
       border_nocolor(win[CAL].p);
-    wins_calendar_unlock();
+    WINS_CALENDAR_UNLOCK;
   }
   if (flags & FLAG_APP) {
     if (slctd_win == APP)