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

10 files changed, 197 insertions, 15 deletions

diff --git a/nuttx/sched/Kconfig b/nuttx/sched/Kconfig
index bfaec3b5d..69621a1fa 100644
--- a/nuttx/sched/Kconfig
+++ b/nuttx/sched/Kconfig
@@ -38,6 +38,16 @@ config TASK_NAME_SIZE
 		Useful if scheduler instrumentation is selected.  Set to zero to
 		disable.
 
+config SCHED_HAVE_PARENT
+	bool "Remember Parent"
+	default n
+	---help---
+		Remember the ID of the parent thread when a new child thread is
+		created.  This support enables a few minor features (such as
+		SIGCHLD) and slightly increases the size of the Task Control Block
+		(TCB) of every task to hold the ID of the parent thread.  Default:
+		disabled.
+
 config JULIAN_TIME
 	bool "Enables Julian time conversions"
 	default n
@@ -127,6 +137,7 @@ config SDCLONE_DISABLE
 config SCHED_WORKQUEUE
 	bool "Enable worker thread"
 	default n
+	depends on !DISABLE_SIGNALS
 	---help---
 		Create a dedicated "worker" thread to handle delayed processing from interrupt
 		handlers.  This feature is required for some drivers but, if there are no
@@ -158,14 +169,6 @@ config SCHED_WORKSTACKSIZE
 	---help---
 		The stack size allocated for the worker thread.  Default: 2K.
 
-config SIG_SIGWORK
-	int "Worker thread wakeup signal"
-	default 4
-	depends on SCHED_WORKQUEUE
-	---help---
-		The signal number that will be used to wake-up the worker thread.
-		Default: 4
-
 config SCHED_LPWORK
 	bool "Enable a lower priority worker thread"
 	default n
@@ -310,6 +313,56 @@ config DISABLE_POLL
 	depends on DISABLE_OS_API
 	default n
 
+if !DISABLE_SIGNALS
+comment "Signal Numbers"
+
+config SIG_SIGUSR1
+	int "SIGUSR1"
+	default 1
+	---help---
+		Value of standard user signal 1 (SIGUSR1). Default: 1
+
+config SIG_SIGUSR2
+	int "SIGUSR2"
+	default 2
+	---help---
+		Value of standard user signal 2 (SIGUSR2). Default: 2
+
+config SIG_SIGALARM
+	int "SIGALRM"
+	default 3
+	---help---
+		Default the signal number used with POSIX timers (SIGALRM).
+		Default: 3
+
+config SIG_SIGCHLD
+	int "SIGCHLD"
+	default 4
+	depends on SCHED_HAVE_PARENT
+	---help---
+		The SIGCHLD signal is sent to the parent of a child process when it
+		exits, is interrupted (stopped), or resumes after being interrupted.
+		Default: 4
+
+config SIG_SIGCONDTIMEDOUT
+	int "SIGCONDTIMEDOUT"
+	default 16
+	depends on !DISABLE_PTHREAD
+	---help---
+		This non-standard signal number is used the implementation of
+		pthread_cond_timedwait(). Default 16.
+
+config SIG_SIGWORK
+	int "SIGWORK"
+	default 17
+	depends on SCHED_WORKQUEUE
+	---help---
+		SIGWORK is a non-standard signal used to wake up the internal NuttX
+		worker thread.  This setting specifies the signal number that will be
+		used for SIGWORK.  Default: 17
+
+endif
+
 comment "Sizes of configurable things (0 disables)"
 
 config MAX_TASKS
diff --git a/nuttx/sched/sched_unlock.c b/nuttx/sched/sched_unlock.c
index 9a52e8358..5eafcfc9e 100644
--- a/nuttx/sched/sched_unlock.c
+++ b/nuttx/sched/sched_unlock.c
@@ -126,5 +126,6 @@ int sched_unlock(void)
 
       irqrestore(flags);
     }
+
   return OK;
 }
diff --git a/nuttx/sched/sig_kill.c b/nuttx/sched/sig_kill.c
index 17921015f..b3d74d8a1 100644
--- a/nuttx/sched/sig_kill.c
+++ b/nuttx/sched/sig_kill.c
@@ -84,6 +84,9 @@
 
 int kill(pid_t pid, int signo)
 {
+#ifdef CONFIG_SCHED_HAVE_PARENT
+  FAR _TCB *rtcb = (FAR _TCB *)g_readytorun.head;
+#endif
   FAR _TCB *stcb;
   siginfo_t info;
   int       ret = ERROR;
@@ -124,6 +127,10 @@ int kill(pid_t pid, int signo)
   info.si_signo           = signo;
   info.si_code            = SI_USER;
   info.si_value.sival_ptr = NULL;
+#ifdef CONFIG_SCHED_HAVE_PARENT
+  info.si_pid             = rtcb->pid;
+  info.si_status          = OK;
+#endif
 
   /* Send the signal */
 
diff --git a/nuttx/sched/sig_mqnotempty.c b/nuttx/sched/sig_mqnotempty.c
index 9a1fd7243..f7ae6fd0d 100644
--- a/nuttx/sched/sig_mqnotempty.c
+++ b/nuttx/sched/sig_mqnotempty.c
@@ -88,6 +88,9 @@ int sig_mqnotempty (int pid, int signo, union sigval value)
 int sig_mqnotempty (int pid, int signo, void *sival_ptr)
 #endif
 {
+#ifdef CONFIG_SCHED_HAVE_PARENT
+  FAR _TCB *rtcb = (FAR _TCB *)g_readytorun.head;
+#endif
   FAR _TCB *stcb;
   siginfo_t info;
   int       ret = ERROR;
@@ -113,6 +116,10 @@ int sig_mqnotempty (int pid, int signo, void *sival_ptr)
 #else
   info.si_value.sival_ptr = sival_ptr;
 #endif
+#ifdef CONFIG_SCHED_HAVE_PARENT
+  info.si_pid             = rtcb->pid;
+  info.si_status          = OK;
+#endif
 
   /* Verify that we can perform the signalling operation */
 
diff --git a/nuttx/sched/sig_queue.c b/nuttx/sched/sig_queue.c
index dee1c798a..db404238e 100644
--- a/nuttx/sched/sig_queue.c
+++ b/nuttx/sched/sig_queue.c
@@ -111,6 +111,9 @@ int sigqueue (int pid, int signo, union sigval value)
 int sigqueue(int pid, int signo, void *sival_ptr)
 #endif
 {
+#ifdef CONFIG_SCHED_HAVE_PARENT
+  FAR _TCB *rtcb = (FAR _TCB *)g_readytorun.head;
+#endif
   FAR _TCB *stcb;
   siginfo_t info;
   int       ret = ERROR;
@@ -142,13 +145,17 @@ int sigqueue(int pid, int signo, void *sival_ptr)
 
   /* Create the siginfo structure */
 
-  info.si_signo = signo;
-  info.si_code  = SI_QUEUE;
+  info.si_signo           = signo;
+  info.si_code            = SI_QUEUE;
 #ifdef CONFIG_CAN_PASS_STRUCTS
-  info.si_value = value;
+  info.si_value           = value;
 #else
   info.si_value.sival_ptr = sival_ptr;
 #endif
+#ifdef CONFIG_SCHED_HAVE_PARENT
+  info.si_pid             = rtcb->pid;
+  info.si_status          = OK;
+#endif
 
   /* Send the signal */
 
diff --git a/nuttx/sched/sig_timedwait.c b/nuttx/sched/sig_timedwait.c
index d7610cd49..b07b8f2a1 100644
--- a/nuttx/sched/sig_timedwait.c
+++ b/nuttx/sched/sig_timedwait.c
@@ -120,6 +120,10 @@ static void sig_timeout(int argc, uint32_t itcb)
       u.wtcb->sigunbinfo.si_signo           = SIG_WAIT_TIMEOUT;
       u.wtcb->sigunbinfo.si_code            = SI_TIMER;
       u.wtcb->sigunbinfo.si_value.sival_int = 0;
+#ifdef CONFIG_SCHED_HAVE_PARENT
+      u.wtcb->sigunbinfo.si_pid             = 0;  /* Not applicable */
+      u.wtcb->sigunbinfo.si_status          = OK;
+#endif
       up_unblock_task(u.wtcb);
     }
 }
diff --git a/nuttx/sched/task_deletecurrent.c b/nuttx/sched/task_deletecurrent.c
index 77025f5e0..7ecfb26cc 100644
--- a/nuttx/sched/task_deletecurrent.c
+++ b/nuttx/sched/task_deletecurrent.c
@@ -90,6 +90,9 @@
  * Return Value:
  *   OK on success; or ERROR on failure
  *
+ * Assumeptions:
+ *   Interrupts are disabled.
+ *
  ****************************************************************************/
 
 int task_deletecurrent(void)
@@ -108,7 +111,7 @@ int task_deletecurrent(void)
   (void)sched_removereadytorun(dtcb);
   rtcb = (FAR _TCB*)g_readytorun.head;
 
-  /* We are not in a bad state -- the head of the ready to run task list
+  /* We are now in a bad state -- the head of the ready to run task list
    * does not correspond to the thread that is running.  Disabling pre-
    * emption on this TCB and marking the new ready-to-run task as not
    * running (see, for example, get_errno_ptr()).
@@ -132,9 +135,16 @@ int task_deletecurrent(void)
       (void)sched_mergepending();
     }
 
-  /* Now calling sched_unlock() should have no effect */
+  /* We can't use sched_unlock() to decrement the lock count because the
+   * sched_mergepending() call above might have changed the task at the
+   * head of the ready-to-run list.  Furthermore, we should not need to
+   * perform the unlock action anyway because we know that the pending
+   * task list is empty.  So all we really need to do is to decrement
+   * the lockcount on rctb.
+   */
 
-  sched_unlock();
+  DEBUGASSERT(rtcb->lockcount > 0);
+  rtcb->lockcount--;
   return OK;
 }
 
diff --git a/nuttx/sched/task_exithook.c b/nuttx/sched/task_exithook.c
index 3bde8fb7a..9ce2e5899 100644
--- a/nuttx/sched/task_exithook.c
+++ b/nuttx/sched/task_exithook.c
@@ -41,6 +41,7 @@
 
 #include <stdlib.h>
 #include <unistd.h>
+#include <signal.h>
 #include <debug.h>
 #include <errno.h>
 
@@ -188,6 +189,56 @@ static inline void task_onexit(FAR _TCB *tcb, int status)
 #endif
 
 /****************************************************************************
+ * Name: task_sigchild
+ *
+ * Description:
+ *   Send the SIGCHILD signal to the parent thread
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_SCHED_HAVE_PARENT
+static inline void task_sigchild(FAR _TCB *tcb, int status)
+{
+  FAR _TCB *ptcb;
+  siginfo_t info;
+
+  /* Keep things stationary through the following */
+
+  sched_lock();
+
+  /* Get the TCB of the receiving task */
+
+  ptcb = sched_gettcb(tcb->parent);
+  if (!ptcb)
+    {
+      /* The parent no longer exists... bail */
+
+      sched_unlock();
+      return;
+    }
+
+  /* Create the siginfo structure.  We don't actually know the cause.  That
+   * is a bug. Let's just say that the child task just exit-ted for now.
+   */
+
+  info.si_signo           = SIGCHLD;
+  info.si_code            = CLD_EXITED;
+  info.si_value.sival_ptr = NULL;
+  info.si_pid             = tcb->pid;
+  info.si_status          = status;
+
+  /* Send the signal.  We need to use this internal interface so that we can
+   * provide the correct si_code value with the signal.
+   */
+
+  (void)sig_received(ptcb, &info);
+  sched_unlock();
+}
+#else
+#  define task_sigchild(tcb,status)
+#endif
+
+/****************************************************************************
  * Name: task_exitwakeup
  *
  * Description:
@@ -259,6 +310,10 @@ void task_exithook(FAR _TCB *tcb, int status)
 
   task_atexit(tcb);
 
+  /* Send SIGCHLD to the parent of the exiting task */
+
+  task_sigchild(tcb, status);
+
   /* Call any registered on_exit function(s) */
 
   task_onexit(tcb, status);
diff --git a/nuttx/sched/task_setup.c b/nuttx/sched/task_setup.c
index 8721b39ec..c5dd8ca3a 100644
--- a/nuttx/sched/task_setup.c
+++ b/nuttx/sched/task_setup.c
@@ -147,6 +147,34 @@ static int task_assignpid(FAR _TCB *tcb)
 }
 
 /****************************************************************************
+ * Name: task_saveparent
+ *
+ * Description:
+ *   Save the task ID of the parent task in the child task's TCB.
+ *
+ * Parameters:
+ *   tcb - The TCB of the new, child task.
+ *
+ * Returned Value:
+ *   None
+ *
+ * Assumptions:
+ *   The parent of the new task is the task at the head of the ready-to-run
+ *   list.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_SCHED_HAVE_PARENT
+static inline void task_saveparent(FAR _TCB *tcb)
+{
+  FAR _TCB *rtcb = (FAR _TCB*)g_readytorun.head;
+  tcb->parent = rtcb->pid;
+}
+#else
+#  define task_saveparent(tcb)
+#endif
+
+/****************************************************************************
  * Name: task_dupdspace
  *
  * Description:
@@ -161,6 +189,8 @@ static int task_assignpid(FAR _TCB *tcb)
  *   None
  *
  * Assumptions:
+ *   The parent of the new task is the task at the head of the ready-to-run
+ *   list.
  *
  ****************************************************************************/
 
@@ -231,6 +261,10 @@ int task_schedsetup(FAR _TCB *tcb, int priority, start_t start, main_t main)
       tcb->start          = start;
       tcb->entry.main     = main;
 
+      /* Save the task ID of the parent task in the TCB */
+
+      task_saveparent(tcb);
+
       /* exec(), pthread_create(), task_create(), and vfork() all
        * inherit the signal mask of the parent thread.
        */
@@ -243,7 +277,7 @@ int task_schedsetup(FAR _TCB *tcb, int priority, start_t start, main_t main)
        * until it is activated.
        */
 
-      tcb->task_state   = TSTATE_TASK_INVALID;
+      tcb->task_state = TSTATE_TASK_INVALID;
 
       /* Clone the parent tasks D-Space (if it was running PIC).  This
        * must be done before calling up_initial_state() so that the
diff --git a/nuttx/sched/timer_settime.c b/nuttx/sched/timer_settime.c
index 1814ba898..f09842ad4 100644
--- a/nuttx/sched/timer_settime.c
+++ b/nuttx/sched/timer_settime.c
@@ -113,6 +113,10 @@ static void inline timer_sigqueue(FAR struct posix_timer_s *timer)
 #else
        info.si_value.sival_ptr = timer->pt_value.sival_ptr;
 #endif
+#ifdef CONFIG_SCHED_HAVE_PARENT
+       info.si_pid             = 0;  /* Not applicable */
+       info.si_status          = OK;
+#endif
 
        /* Send the signal */