JackControlAPI: Replacing sigwait with signalfd and poll

This would be required so that the polling concept can be used to wait
on signals as well as wait for events from the other threads.

Signed-off-by: Laxmi Devi <Laxmi.Devi@in.bosch.com>

common/JackControlAPI.cpp

@@ -26,6 +26,11 @@
 #include <pthread.h>
 #endif
 
+#ifdef __linux__
+#include <poll.h>
+#include <sys/signalfd.h>
+#endif
+
 #include "types.h"
 #include <string.h>
 #include <errno.h>
@@ -677,16 +682,56 @@ jackctl_setup_signals(
 SERVER_EXPORT void
 jackctl_wait_signals(jackctl_sigmask_t * sigmask)
 {
-    int sig;
+    int sig = 0;
     bool waiting = true;
+#ifdef __linux__
+    int err;
+    struct pollfd pfd;
+    struct signalfd_siginfo si;
+
+    /* Block the signals in order for signalfd to receive them */
+    sigprocmask(SIG_BLOCK, &sigmask->signals, NULL);
+
+    pfd.fd = signalfd(-1, &sigmask->signals, 0);
+    if(pfd.fd == -1) {
+        fprintf(stderr, "Jack : signalfd() failed with errno %d\n", -errno);
+        return;
+    }
+    pfd.events = POLLIN;
+#endif
 
     while (waiting) {
     #if defined(sun) && !defined(__sun__) // SUN compiler only, to check
         sigwait(&sigmask->signals);
+        fprintf(stderr, "Jack main caught signal\n");
+    #elif defined(__linux__)
+        err = poll(&pfd, 1, -1);
+        if (err < 0) {
+            if (errno == EINTR) {
+                continue;
+            } else {
+                fprintf(stderr, "Jack : poll() failed with errno %d\n", -errno);
+                break;
+            }
+        } else {
+            if (pfd.revents & (POLLERR | POLLHUP | POLLNVAL)) {
+                fprintf(stderr, "Jack : poll() exited with errno %d\n", -errno);
+                break;
+            } else if ((pfd.revents & POLLIN) == 0) {
+                continue;
+            }
+            err = read (pfd.fd, &si, sizeof(si));
+            if (err < 0) {
+                fprintf(stderr, "Jack : read() on signalfd failed with errno %d\n", -errno);
+                goto fail;
+            }
+            sig = si.ssi_signo;
+            fprintf(stderr, "Jack main caught signal %d\n", sig);
+        }
     #else
         sigwait(&sigmask->signals, &sig);
-    #endif
         fprintf(stderr, "Jack main caught signal %d\n", sig);
+    #endif
 
         switch (sig) {
             case SIGUSR1:
@@ -710,6 +755,12 @@ jackctl_wait_signals(jackctl_sigmask_t * sigmask)
         // bugs that cause segfaults etc. during shutdown.
         sigprocmask(SIG_UNBLOCK, &sigmask->signals, 0);
     }
+
+#ifdef __linux__
+fail:
+    close(pfd.fd);
+#endif
+
 }
 #endif