use sigtimedwait instead of pthread_cond_timedwait

pthread mutexes should not be used inside signal handlers

diff --git a/configure.ac b/configure.ac
index 4630c7c..b2c71c9 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -12,9 +12,6 @@ AC_CONFIG_HEADERS([config.h])
 AC_PROG_CC
 AC_PROG_INSTALL
 
-# FIXME: Replace `main' with a function in `-lpthread':
-AC_CHECK_LIB([pthread], [main], ,
-            AC_MSG_ERROR([libpthread is required but was not found]))
 # FIXME: Replace `main' with a function in `-lrt':
 AC_CHECK_LIB([rt], [main], ,
             AC_MSG_ERROR([librt is required but was not found]))

diff --git a/src/main.c b/src/main.c
index 49e2d43..f14b5fd 100644 (file)
--- a/src/main.c
+++ b/src/main.c
@@ -22,8 +22,9 @@
 #include <stdlib.h>
 #include <string.h>
 #include <signal.h>
-#include <pthread.h>
 #include <string.h>
+#include <time.h>
+#include <assert.h>
 #include <linux/limits.h>
 #include <linux/vt.h>
 #include <linux/kd.h>
@@ -33,23 +34,8 @@
 #include <systemd/sd-daemon.h>
 
 
-static pthread_mutex_t notify_mutex = PTHREAD_MUTEX_INITIALIZER;
-static pthread_cond_t notify_condition = PTHREAD_COND_INITIALIZER;
-
 static int xpid;
 
-static void usr1handler(int foo)
-{
-       /* Got the signal from the X server that it's ready */
-       if (foo++) foo--;
-
-       sd_notify(0, "READY=1");
-
-       pthread_mutex_lock(&notify_mutex);
-       pthread_cond_signal(&notify_condition);
-       pthread_mutex_unlock(&notify_mutex);
-}
-
 static void termhandler(int foo)
 {
        if (foo++) foo--;
@@ -57,10 +43,8 @@ static void termhandler(int foo)
        kill(xpid, SIGTERM);
 }
 
-
 int main(int argc, char **argv)
 {
-       struct sigaction usr1;
        struct sigaction term;
        char *xserver = NULL;
        char *ptrs[32];
@@ -68,34 +52,63 @@ int main(int argc, char **argv)
        pid_t pid;
        char all[PATH_MAX] = "";
        int i;
-
-       /* Step 1: arm the signal */
-       memset(&usr1, 0, sizeof(struct sigaction));
-       usr1.sa_handler = usr1handler;
-       sigaction(SIGUSR1, &usr1, NULL);
+       sigset_t mask;
+       sigset_t oldmask;
+       /* Step 1: block sigusr1 until we wait for it */
+       sigemptyset(&mask);
+       sigaddset(&mask, SIGUSR1);
+       sigprocmask(SIG_BLOCK, &mask, &oldmask);
 
        /* Step 2: fork */
        pid = fork();
        if (pid) {
-               struct timespec tv;
-               int err;
+               struct timespec starttime;
+               struct timespec timeout;
                int status;
 
                xpid = pid;
 
-               /* setup sighandler for main thread */
-               clock_gettime(CLOCK_REALTIME, &tv);
-               tv.tv_sec += 10;
-
-               pthread_mutex_lock(&notify_mutex);
-               err = pthread_cond_timedwait(&notify_condition, &notify_mutex, &tv);
-               pthread_mutex_unlock(&notify_mutex);
-
-               if (err == ETIMEDOUT) {
-                       fprintf(stderr, "X server startup timed out (10secs). This indicates an"
-                               "an issue in the server configuration or drivers.\n");
-                       exit(EXIT_FAILURE);
-               }
+               /* wait up to 10 seconds for X server to start */
+               clock_gettime(CLOCK_REALTIME, &starttime);
+               timeout.tv_sec = 10;
+               timeout.tv_nsec = 0;
+               do {
+                       int ret =  sigtimedwait(&mask, NULL, &timeout);
+                       if (ret > 0) {
+                               assert(ret == SIGUSR1);
+                               /* got SIGUSR1, X server has started */
+                               sd_notify(0, "READY=1");
+                               break;
+                       }
+                       else if (errno == EINTR) {
+                               struct timespec currenttime;
+                               /* interrupted by other signal, update timeout and retry */
+                               clock_gettime(CLOCK_REALTIME, &currenttime);
+                               timeout.tv_sec = (starttime.tv_sec + 10) - currenttime.tv_sec;
+                               if (currenttime.tv_nsec > starttime.tv_nsec) {
+                                       timeout.tv_nsec = starttime.tv_nsec + 1000000000L - currenttime.tv_nsec;
+                                       timeout.tv_sec--;
+                               }
+                               else {
+                                       timeout.tv_nsec = currenttime.tv_nsec - starttime.tv_nsec ;
+                               }
+                               /* printf("New timeout: %d s, %d ns\n",
+                                       (int)timeout.tv_sec, (int)timeout.tv_nsec); */
+                               if (timeout.tv_sec < 0 || timeout.tv_nsec < 0) {
+                                       timeout.tv_sec = 0;
+                                       timeout.tv_nsec = 0;
+                               }
+                       }
+                       else if (errno == EAGAIN) {
+                               fprintf(stderr, "X server startup timed out (10secs). This "
+                                       "indicates an issue in the server configuration or drivers.\n");
+                               exit(EXIT_FAILURE);
+                       }
+                       else {
+                               perror("sigtimedwait");
+                               exit(EXIT_FAILURE);
+                       }
+               } while (1);
 
                /* handle TERM gracefully and pass it on to xpid */
                memset(&term, 0, sizeof(struct sigaction));
@@ -112,9 +125,10 @@ int main(int argc, char **argv)
        /* if we get here we're the child */
 
        /*
-        * set the X server sigchld to SIG_IGN, that's the
-         * magic to make X send the parent the signal.
+        * reset signal mask and set the X server sigchld to SIG_IGN, that's the
+        * magic to make X send the parent the signal.
         */
+       sigprocmask(SIG_SETMASK, &oldmask, NULL);
        signal(SIGUSR1, SIG_IGN);
 
        /* Step 3: find the X server */
@@ -143,9 +157,8 @@ int main(int argc, char **argv)
                        strncat(all, " ", PATH_MAX - strlen(all) - 1);
        }
 
-       fprintf(stderr, "Starting Xorg server with: \"%s\"", all);
+       fprintf(stderr, "Starting Xorg server with: \"%s\"\n", all);
        execv(ptrs[0], ptrs);
        fprintf(stderr, "Failed to execv() the X server.\n");
-
        exit(EXIT_FAILURE);
 }