libhsakmt: Improve error handling in child process

Check for errno == EBADF in kmtIoctl to detect misuse of the kfd_fd
in a forked child process.

Detect being in a forked child process pro-actively by implementing
a pthread_atfork callback.

Make sure all mutexes get reinitialized in the child process to avoid
deadlocks.

Check for being in a forked child process in CHECK_KFD_OPENED so that
all hsaKmt functions will return the appropriate status
HSAKMT_STATUS_KERNEL_IO_CHANNEL_NOT_OPENED.

Update InvalidKFDHandleTest to expect that error code.

Change-Id: I0238e5fba344dcaa454e97a35db2e2dcc8d1f607
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>

src/libhsakmt.c

@@ -1,3 +1,4 @@
+#include <stdio.h>
 #include <errno.h>
 #include <sys/ioctl.h>
 
@@ -12,5 +13,13 @@ int kmtIoctl(int fd, unsigned long request, void *arg)
 		ret = ioctl(fd, request, arg);
 	} while (ret == -1 && (errno == EINTR || errno == EAGAIN));
 
+	if (errno == EBADF) {
+		/* In case pthread_atfork didn't catch it, this will
+		 * make any subsequent hsaKmt calls fail in CHECK_KFD_OPEN.
+		 */
+		pr_err("KFD file descriptor not valid in this process\n");
+		hsakmt_forked = true;
+	}
+
 	return ret;
 }