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Fix separate USR1 handling & time display logic

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Make remaining_time() more atomic, in order to avoid receiving a signal
during execution of this function.

Receiving a signal during a signal handler is an undefined behavior.
This commit is contained in:
Simon Lieb 2016-10-25 20:23:05 +02:00 committed by Ivan Tham
parent 50ed6952f2
commit 3678854ad1
1 changed files with 24 additions and 12 deletions
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36
spt.c
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@ -24,14 +24,15 @@ typedef struct {
#include "config.h"
static int i, timecount, suspend;
volatile static sig_atomic_t display, suspend;
/* function declarations */
static void die(const char *errstr, ...);
static void spawn(char *cmd, char *cmt);
static void notify_send(char *cmt);
static void remaining_time(int sigint);
static void toggle(int sigint);
static void display_time(int timecount);
static void toggle_display(int sigint);
static void toggle_suspend(int sigint);
static void usage(void);
/* functions implementations */
@ -78,21 +79,27 @@ notify_send(char *cmt)
}
void
remaining_time(int sigint)
display_time(int timecount)
{
char buf[17];
// FIXME: signal handlers should only do very few things, like
// setting volatile sig_atomic_t
snprintf(buf, 17, "Remaining: %02d:%02d\n",
(timers[i].tmr - timecount) / 60,
(timers[i].tmr - timecount) % 60);
timecount / 60,
timecount % 60);
notify_send(buf);
display = 0;
}
void
toggle(int sigint) {
toggle_display(int sigint)
{
display = 1;
}
void
toggle_suspend(int sigint)
{
suspend ^= 1;
}
@ -107,6 +114,7 @@ main(int argc, char *argv[])
{
struct sigaction sa;
sigset_t emptymask;
int i, timecount;
ARGBEGIN {
case 'e':
@ -124,7 +132,7 @@ main(int argc, char *argv[])
} ARGEND;
/* add SIGUSR1 handler: remaining_time */
sa.sa_handler = remaining_time;
sa.sa_handler = toggle_display;
sigemptyset(&sa.sa_mask);
sa.sa_flags = 0;
@ -132,7 +140,7 @@ main(int argc, char *argv[])
die("cannot associate SIGUSR1 to handler\n");
/* add SIGUSR2 handler: toggle */
sa.sa_handler = toggle;
sa.sa_handler = toggle_suspend;
sigemptyset(&sa.sa_mask);
sa.sa_flags = 0;
@ -142,7 +150,10 @@ main(int argc, char *argv[])
for (i = 0; ; i = (i + 1) % LEN(timers)) {
notify_send(timers[i].cmt);
timecount = 0;
while (timecount < timers[i].tmr)
while (timecount < timers[i].tmr) {
if (display)
display_time(timecount);
if (suspend)
sigsuspend(&emptymask);
else {
@ -150,6 +161,7 @@ main(int argc, char *argv[])
timecount++;
}
}
}
return 0;
}