[LTP] Make userfaultfd0{1, 3, 4} LTP tests valgrind compatible

[linuxtestproject.agent@gmail.com]

Hi Martin,

On Tue, 21 Apr 2026, Martin Cermak wrote:
> Make userfaultfd0{1, 3, 4} LTP tests valgrind compatible

The commit message is missing a Signed-off-by: tag.

> -static void *handle_thread(void)
> +static void *pagefault_handler(void)

Since this is no longer a thread entry point, change the return type to
void and drop the return NULL.

> /*\
>  * Force a pagefault event and handle it using :manpage:`userfaultfd(2)`
>  * from a different thread.
>  */

The handler now runs in a forked child, not a thread. Update the doc
comment in all three files.

[...]

> +	pid = SAFE_FORK();
> +		if (pid == 0) {
> +		pagefault_handler();

userfaultfd03.c: extra leading tab on the `if` line.

[...]

> +	SAFE_WAITPID(pid, NULL, 0);
>  	reset_pages();

In the original code the thread closed uffd for the whole process (threads
share the fd table). With fork, the child closes only its own copy; the
parent's uffd is never closed. Add SAFE_CLOSE(uffd) before reset_pages()
in all three tests.

Also, tst_safe_pthread.h is no longer used in userfaultfd03.c and
userfaultfd04.c after this change; remove the include.

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