Fix a *critical* bug in the task exit logic. Implements SIGCHILD

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@5513 42af7a65-404d-4744-a932-0658087f49c3

2 files changed, 60 insertions, 0 deletions

diff --git a/apps/ChangeLog.txt b/apps/ChangeLog.txt
index 6b63527a7..65d4d6134 100644
--- a/apps/ChangeLog.txt
+++ b/apps/ChangeLog.txt
@@ -462,4 +462,6 @@
 	* apps/examples/wlan: Remove non-functional example.
 	* apps/examples/ostest/vfork.c:  Added a test of vfork().
 	* apps/exampes/posix_spawn: Added a test of poxis_spawn().
+	* apps/examples/ostest:  Extend signal handler test to catch
+	  death-of-child signals (SIGCHLD).
 
diff --git a/apps/examples/ostest/sighand.c b/apps/examples/ostest/sighand.c
index eabfe5646..63d9590d9 100644
--- a/apps/examples/ostest/sighand.c
+++ b/apps/examples/ostest/sighand.c
@@ -54,12 +54,32 @@ static sem_t sem;
 static bool sigreceived = false;
 static bool threadexited = false;
 
+#ifdef CONFIG_SCHED_HAVE_PARENT
+static void death_of_child(int signo, siginfo_t *info, void *ucontext)
+{
+  /* Use of printf in a signal handler is NOT safe! It can cause deadlocks! */
+
+  if (info)
+    {
+      printf("death_of_child: PID %d received signal=%d code=%d pid=%d status=%d\n",
+             getpid(), signo, info->si_code, info->si_pid, info->si_status);
+    }
+  else
+    {
+      printf("death_of_child: PID %d received signal=%d (no info?)\n",
+             getpid(), signo);
+    }
+}
+#endif
+
 static void wakeup_action(int signo, siginfo_t *info, void *ucontext)
 {
   sigset_t oldset;
   sigset_t allsigs;
   int status;
 
+  /* Use of printf in a signal handler is NOT safe! It can cause deadlocks! */
+
   printf("wakeup_action: Received signal %d\n" , signo);
 
   sigreceived = true;
@@ -186,6 +206,11 @@ static int waiter_main(int argc, char *argv[])
 
 void sighand_test(void)
 {
+#ifdef CONFIG_SCHED_HAVE_PARENT
+  struct sigaction act;
+  struct sigaction oact;
+  sigset_t sigset;
+#endif
   struct sched_param param;
   union sigval sigvalue;
   pid_t waiterpid;
@@ -195,6 +220,32 @@ void sighand_test(void)
   printf("sighand_test: Initializing semaphore to 0\n" );
   sem_init(&sem, 0, 0);
 
+#ifdef CONFIG_SCHED_HAVE_PARENT
+  printf("sighand_test: Unmasking SIGCHLD\n");
+
+  (void)sigemptyset(&sigset);
+  (void)sigaddset(&sigset, SIGCHLD);
+  status = sigprocmask(SIG_UNBLOCK, &sigset, NULL);
+  if (status != OK)
+    {
+      printf("sighand_test: ERROR sigprocmask failed, status=%d\n",
+              status);
+    }
+
+  printf("sighand_test: Registering SIGCHLD handler\n" );
+  act.sa_sigaction = death_of_child;
+  act.sa_flags  = SA_SIGINFO;
+
+  (void)sigfillset(&act.sa_mask);
+  (void)sigdelset(&act.sa_mask, SIGCHLD);
+
+  status = sigaction(SIGCHLD, &act, &oact);
+  if (status != OK)
+    {
+      printf("waiter_main: ERROR sigaction failed, status=%d\n" , status);
+    }
+#endif
+
   /* Start waiter thread  */
 
   printf("sighand_test: Starting waiter task\n" );
@@ -262,6 +313,13 @@ void sighand_test(void)
       printf("sighand_test: ERROR signal handler did not run\n" );
     }
 
+  /* Detach the signal handler */
+
+#ifdef CONFIG_SCHED_HAVE_PARENT
+  act.sa_sigaction = SIG_DFL;
+  status = sigaction(SIGCHLD, &act, &oact);
+#endif
+
   printf("sighand_test: done\n" );
   FFLUSH();
 }