POSIX: px4_getpid() fix

Since the PX4 code uses both px4_task and pthread APIs,
px4_getpid() must be save to call from either context.

On posix, this means we have to always return the pthread ID.

Reverted simulator change of pthread to px4_task

There may have been side effects if this was build for a target that
has process/task scoped file descriptors. It is now safe to call
px4_getpid() from this pthread context with this change for the
posix build for px4_getpid().

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

src/platforms/posix/px4_layer/px4_posix_tasks.cpp

@@ -278,21 +278,9 @@ void px4_show_tasks()
 
 __BEGIN_DECLS
 
-int px4_getpid()
+unsigned long px4_getpid()
 {
-	pthread_t pid = pthread_self();
-
-	if (pid == _shell_task_id)
-		return SHELL_TASK_ID;
-
-	// Get pthread ID from the opaque ID
-	for (int i=0; i<PX4_MAX_TASKS; ++i) {
-		if (taskmap[i].isused && taskmap[i].pid == pid) {
-			return i;
-		}
-	}
-	PX4_ERR("px4_getpid() called from unknown thread context!");
-	return -EINVAL;
+	return (unsigned long)pthread_self();
 }
 
 const char *getprogname();

src/platforms/px4_posix.h

@@ -99,7 +99,7 @@ __EXPORT int		px4_ioctl(int fd, int cmd, unsigned long arg);
 __EXPORT int		px4_poll(px4_pollfd_struct_t *fds, nfds_t nfds, int timeout);
 __EXPORT int		px4_fsync(int fd);
 __EXPORT int		px4_access(const char *pathname, int mode);
-__EXPORT int		px4_getpid(void);
+__EXPORT unsigned long	px4_getpid(void);
 
 __END_DECLS
 #else