waitpid(): Move some logic inside of a critical section

git-svn-id: https://nuttx.svn.sourceforge.net/svnroot/nuttx/trunk@5054 7fd9a85b-ad96-42d3-883c-3090e2eb8679

nuttx/ChangeLog

@@ -3183,3 +3183,5 @@
 	  Fix some strange (and probably wrong) list handling when
 	  CONFIG_PRIORITY_INHERITANCE and CONFIG_SEM_PREALLOCHOLDERS are defined.
 	  This list handling was probably causing errors reported by Mike Smith
+	* sched/sched_waitpid.c: Fix a possible issue with logic logic that
+	  should be brought into a critical section (suggested by Mike Smith)

nuttx/sched/sched_waitpid.c

@@ -178,7 +178,7 @@
 
 pid_t waitpid(pid_t pid, int *stat_loc, int options)
 {
-  _TCB *tcb = sched_gettcb(pid);
+  _TCB *tcb;
   bool mystat;
   int err;
   int ret;
@@ -186,6 +186,7 @@ pid_t waitpid(pid_t pid, int *stat_loc, int options)
   /* Disable pre-emption so that nothing changes in the following tests */
 
   sched_lock();
+  tcb = sched_gettcb(pid);
   if (!tcb)
     {
       err = ECHILD;