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calcurse-edge/src/vars.c
Lars Henriksen 5e53708648 Solve deadlock in notification bar 
calcurse deadlocks when

1) an upcoming appointment is on display in the notification bar,
2) an external command (like help) is started,
3) the time for the upcoming appointment arrives, and
4) the external command is exited.

The notification bar thread is stopped while the external command is
running. Upon exit from the external command, the n-bar thread is
restarted and calcurse locks.

The cause is the way in which the main notification bar thread is
stopped:

static pthread_t notify_t_main;
void notify_stop_main_thread(void)
{
	if (notify_t_main) {
		pthread_cancel(notify_t_main);
		pthread_join(notify_t_main, NULL);
	}
}

Objects of type pthread_t are opaque and should not be accessed
directly.  Initially notify_t_main is an uninitialised static variable
(0), but later it has a value, which may or may not be the thread id of
the notification main thread.

Note that the thread id after exit of a thread may become the thread id
of a new thread. Thus the variable set when the thread is created, is
invalid after exit of the thread.

Specifically, the first time notify_stop_main_thread() is called (by
notify_start_main_thread() before the thread is created) is harmless
(because notify_t_main is 0). Calling notify_stop_main_thread() later
may be either

OK
    because the main thread is running, or
harmless
    because no thread with id notify_t_main is running: the two
    functions will fail with return value ESRCH (no such process), or
fatal
    because an unrelated thread with this thread id is running: it will
    be cancelled, and the join may or may not succeed depending on
    whether the thread is joinable or detached.

The "unrelated thread" could be the next-appointment thread,
notify_thread_app, launched by notify_check_next_app().

Always calling notify_stop_main_thread() before starting the main thread
becomes fatal when notify_check_next_app() is called shortly before
notify_start_main_thread(). This is the case in the scenario described.
The next-app-thread is then running when notify_stop_main_thread() is
called, and apparently it has the thread id of the old main thread
(confirmed by logging the return values from pthread_cancel() and
pthread_join(); the first succeeds while the second fails with EINVALID
which means that the thread is not joinable). The next-app-thread will
therefore exit without unlocking mutexes.

Ensure that notify_t_main, in case the notify main thread is not
running, has a value that it will never have when it is running. A
possibility is the thread id of the main() calcurse process (returned by
pthread_self()).

Check for this condition in notify_stop_main_thread() and set
notify_t_main when the thread is stopped.

Similar changes have been introduced for the periodic save thread and
the calendar date thread.

Signed-off-by: Lars Henriksen <LarsHenriksen@get2net.dk>
Signed-off-by: Lukas Fleischer <lfleischer@calcurse.org>
2018-07-28 14:06:15 +02:00

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/*
* Calcurse - text-based organizer
*
* Copyright (c) 2004-2017 calcurse Development Team <misc@calcurse.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above
* copyright notice, this list of conditions and the
* following disclaimer.
*
* - Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the
* following disclaimer in the documentation and/or other
* materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Send your feedback or comments to : misc@calcurse.org
* Calcurse home page : http://calcurse.org
*
*/
#include <stdlib.h>
#include <string.h>
#include "calcurse.h"
/*
* variables to store window size
*/
int col = 0, row = 0;
int resize = 0;
/* variable to tell if the terminal supports color */
unsigned colorize = 0;
/* Default background and foreground colors. */
int foreground, background;
/*
* To tell if curses interface was launched already or not (in that case
* calcurse is running in command-line mode).
* This is useful to konw how to display messages on the screen.
*/
enum ui_mode ui_mode = UI_CMDLINE;
/* Don't save anything if this is set. */
int read_only = 0;
/* Hide system dialogs if set. */
int quiet = 0;
/* Applications can trigger a reload by sending SIGUSR1. */
int want_reload = 0;
/* Strings describing each input date format. */
const char *datefmt_str[DATE_FORMATS];
/*
* variable to store month lengths
*/
int days[12] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
/*
* variables to store data path names, which are initialized in
* io_init()
*/
char path_dir[] = "";
char path_todo[] = "";
char path_apts[] = "";
char path_conf[] = "";
char path_notes[] = "";
char path_keys[] = "";
char path_cpid[] = "";
char path_dpid[] = "";
char path_dmon_log[] = "";
char path_hooks[] = "";
/* Variable to store global configuration. */
struct conf conf;
/* Variable to handle pads. */
struct pad apad;
/* Variable to store notify-bar settings. */
struct nbar nbar;
/* Variable to store daemon configuration. */
struct dmon_conf dmon;
/*
* Thread id variables for threads that never exit.
*
* Each variable either carries the identifier of the corresponding thread. If
* one of the threads is not running, the corresponding variable is assigned
* the identifier of the main thread instead.
*/
pthread_t notify_t_main, io_t_psave, ui_calendar_t_date;
/*
* Variables init
*/
void vars_init(void)
{
const char *ed, *pg, *mt;
/* Variables for user configuration */
conf.confirm_quit = 1;
conf.confirm_delete = 1;
conf.auto_save = 1;
conf.auto_gc = 0;
conf.periodic_save = 0;
conf.default_panel = CAL;
conf.compact_panels = 0;
conf.system_dialogs = 1;
conf.progress_bar = 1;
strncpy(conf.output_datefmt, "%D", 3);
conf.input_datefmt = 1;
conf.heading_pos = RIGHT;
strcpy(conf.day_heading, DAY_HEADING_DEFAULT);
datefmt_str[0] = _("mm/dd/yyyy");
datefmt_str[1] = _("dd/mm/yyyy");
datefmt_str[2] = _("yyyy/mm/dd");
datefmt_str[3] = _("yyyy-mm-dd");
/* Default external editor and pager */
ed = getenv("CALCURSE_EDITOR");
if (ed == NULL || ed[0] == '\0')
ed = getenv("VISUAL");
if (ed == NULL || ed[0] == '\0')
ed = getenv("EDITOR");
if (ed == NULL || ed[0] == '\0')
ed = DEFAULT_EDITOR;
conf.editor = ed;
pg = getenv("CALCURSE_PAGER");
if (pg == NULL || pg[0] == '\0')
pg = getenv("PAGER");
if (pg == NULL || pg[0] == '\0')
pg = DEFAULT_PAGER;
conf.pager = pg;
mt = getenv("CALCURSE_MERGETOOL");
if (mt == NULL || mt[0] == '\0')
mt = getenv("MERGETOOL");
if (mt == NULL || mt[0] == '\0')
mt = DEFAULT_MERGETOOL;
conf.mergetool = mt;
wins_set_layout(1);
ui_calendar_set_first_day_of_week(MONDAY);
/* Pad structure to scroll text inside the appointment panel */
apad.length = 1;
apad.first_onscreen = 0;
/* Attribute definitions for color and non-color terminals */
custom_init_attr();
/* Start at the current date */
ui_calendar_init_slctd_day();
/* Threads not yet running. */
notify_t_main = io_t_psave = ui_calendar_t_date = pthread_self();
}
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