Improved signal handling by implementing signal blocking

dwmblocks.c

@@ -29,7 +29,6 @@ typedef struct {
 
 static void buttonhandler(int signal, siginfo_t *si, void *ucontext);
 static void getcmd(Block *block, int sigval);
-static void setroot();
 static void setupsignals();
 static void sighandler(int signal, siginfo_t *si, void *ucontext);
 static void statusloop();
@@ -41,6 +40,7 @@ static int statuscontinue = 1;
 static char statusstr[STTLENGTH];
 static size_t delimlength;
 static Display *dpy;
+static sigset_t blocksigmask;
 
 void
 buttonhandler(int signal, siginfo_t *si, void *ucontext)
@@ -111,44 +111,45 @@ getcmd(Block *block, int sigval)
         }
 }
 
-void
-setroot()
-{
-        if (updatestatus()) {
-                XStoreName(dpy, DefaultRootWindow(dpy), statusstr);
-                XFlush(dpy);
-        }
-}
-
 void
 setupsignals()
 {
         struct sigaction sa;
 
-        sigemptyset(&sa.sa_mask);
+        /* to handle HUP, INT and TERM */
         sa.sa_flags = SA_RESTART;
-        /* to handle INT, HUP and TERM */
+        sigemptyset(&sa.sa_mask);
         sa.sa_handler = termhandler;
-        sigaction(SIGINT, &sa, NULL);
         sigaction(SIGHUP, &sa, NULL);
+        sigaction(SIGINT, &sa, NULL);
         sigaction(SIGTERM, &sa, NULL);
+
         /* to ignore unused realtime signals */
+        // sa.sa_flags = SA_RESTART;
+        // sigemptyset(&sa.sa_mask);
         sa.sa_handler = SIG_IGN;
-        for (int i = SIGRTMIN; i <= SIGRTMAX; i++)
+        for (int i = SIGRTMIN + 1; i <= SIGRTMAX; i++)
                 sigaction(i, &sa, NULL);
+
+        /* to prevent forked children from becoming zombies */
+        sa.sa_flags = SA_NOCLDSTOP | SA_NOCLDWAIT | SA_RESTART;
+        // sigemptyset(&sa.sa_mask);
+        sa.sa_handler = SIG_DFL;
+        sigaction(SIGCHLD, &sa, NULL);
+
         /* to handle signals generated by dwm on click events */
         sa.sa_flags = SA_RESTART | SA_SIGINFO;
+        // sigemptyset(&sa.sa_mask);
         sa.sa_sigaction = buttonhandler;
         sigaction(SIGRTMIN, &sa, NULL);
+
         /* to handle update signals for individual blocks */
+        sa.sa_flags |= SA_NODEFER;
+        sa.sa_mask = blocksigmask;
         sa.sa_sigaction = sighandler;
         for (Block *current = blocks; current->pathu; current++)
                 if (current->signal > 0)
                         sigaction(SIGRTMIN + current->signal, &sa, NULL);
-        /* to prevent forked children from becoming zombies */
-        sa.sa_flags = SA_NOCLDWAIT | SA_RESTART;
-        sa.sa_handler = SIG_DFL;
-        sigaction(SIGCHLD, &sa, NULL);
 }
 
 void
@@ -158,26 +159,40 @@ sighandler(int signal, siginfo_t *si, void *ucontext)
         for (Block *current = blocks; current->pathu; current++)
                 if (current->signal == signal)
                         getcmd(current, si->si_value.sival_int);
-        setroot();
+        if (updatestatus()) {
+                XStoreName(dpy, DefaultRootWindow(dpy), statusstr);
+                XSync(dpy, False);
+        }
 }
 
 void
 statusloop()
 {
-        int i;
+        int i = 0;
 
-        setupsignals();
+        /* first run */
         for (Block *current = blocks; current->pathu; current++)
-                if (current->interval >= 0)
+                if (current->interval >= 0) {
+                        sigprocmask(SIG_BLOCK, &blocksigmask, NULL);
                         getcmd(current, NILL);
-        setroot();
-        sleep(SLEEPINTERVAL);
-        i = SLEEPINTERVAL;
+                        sigprocmask(SIG_UNBLOCK, &blocksigmask, NULL);
+                }
+        goto enterloop;
+        /* main loop */
         while (statuscontinue) {
                 for (Block *current = blocks; current->pathu; current++)
-                        if (current->interval > 0 && i % current->interval == 0)
+                        if (current->interval > 0 && i % current->interval == 0) {
+                                sigprocmask(SIG_BLOCK, &blocksigmask, NULL);
                                 getcmd(current, NILL);
-                setroot();
+                                sigprocmask(SIG_UNBLOCK, &blocksigmask, NULL);
+                        }
+enterloop:
+                if (updatestatus()) {
+                        sigprocmask(SIG_BLOCK, &blocksigmask, NULL);
+                        XStoreName(dpy, DefaultRootWindow(dpy), statusstr);
+                        XSync(dpy, False);
+                        sigprocmask(SIG_UNBLOCK, &blocksigmask, NULL);
+                }
                 sleep(SLEEPINTERVAL);
                 i += SLEEPINTERVAL;
         }
@@ -295,6 +310,14 @@ main(int argc, char *argv[])
                 fputs("Error: could not open display.\n", stderr);
                 return 1;
         }
+        sigemptyset(&blocksigmask);
+        sigaddset(&blocksigmask, SIGHUP);
+        sigaddset(&blocksigmask, SIGINT);
+        sigaddset(&blocksigmask, SIGTERM);
+        for (Block *current = blocks; current->pathu; current++)
+                if (current->signal > 0)
+                        sigaddset(&blocksigmask, SIGRTMIN + current->signal);
+        setupsignals();
         statusloop();
         unlink(LOCKFILE);
         XStoreName(dpy, DefaultRootWindow(dpy), "");