Re: [PATCH] selftests/proc: proc-empty-vm: wait for child's SIGSEGV instead of sleep(1)

[Alexey Dobriyan]

On Fri, Oct 23, 2026 at 07:34:33PM +0100, Drif Abdelmalek Mohamed Said wrote:
> The test had a TODO asking for a reliable way to know when the child's
> munmap() has finished, and used sleep(1) in the meantime.
> 
> Unmapping the whole address space leaves the child with no code to run,
> so it segfaults. Since it is traced, the SIGSEGV stop is reported to
> the parent through waitpid(), which is exactly the signal the TODO
> wanted. Wait for it there and drop the sleep and the TODO.
> 
> The stop is now consumed up front, so SIGKILL the child before the
> final reap.

OK I recall what's going on here.

The only thing to worry is child pid reuse but child is under ptrace
so it should be fine.

Reviewed-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>

> +		for (;;) {
> +			p = waitpid(pid, &wstatus, 0);
> +			if (p == -1 && errno == EINTR)
> +				continue;
> +			break;
> +		}

do/while EINTR loops are shorter:

	do {
		rv = f();
	} while (rv == -1 && errno == EINTR);