Re: [PATCH] selftests/mm: handle fork() failure in migration tests

["David Hildenbrand (Arm)" <david@kernel.org>]

On 5/11/26 11:34, Hu Song wrote:
> From: Song Hu <husong@kylinos.cn>
> 
> When fork() fails and returns -1, the code falls into the else branch
> and stores -1 into self->pids[i]. Later, kill(-1, SIGTERM) is called
> which sends SIGTERM to every process the user has permission to signal,
> potentially killing the entire user session.
> 
> Add an explicit check for fork() returning -1 (pid < 0). On failure,
> clean up any already-forked children before failing the test via
> ASSERT_GE(pid, 0). This fix is applied to all three fork() call sites
> in shared_anon, shared_anon_thp, and shared_anon_htlb tests.
> 
> Signed-off-by: Hu Song <husong@kylinos.cn>
> ---
>  tools/testing/selftests/mm/migration.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/tools/testing/selftests/mm/migration.c b/tools/testing/selftests/mm/migration.c
> index 60e78bbfc0e3..f433e4f195ad 100644
> --- a/tools/testing/selftests/mm/migration.c
> +++ b/tools/testing/selftests/mm/migration.c
> @@ -163,6 +163,11 @@ TEST_F_TIMEOUT(migration, shared_anon, 2*RUNTIME)
>  	memset(ptr, 0xde, TWOMEG);
>  	for (i = 0; i < self->nthreads - 1; i++) {
>  		pid = fork();
> +		if (pid < 0) {
> +			while (--i >= 0)
> +				kill(self->pids[i], SIGTERM);



> +			ASSERT_GE(pid, 0);
> +		}
>  		if (!pid) {

I think "else if" reads nicer here.

But why do we care about cleaning up the other processes? IIUC, we don't do that
explicitly if e.g.,

	ASSERT_EQ(migrate(ptr, self->n1, self->n2), 0);

fails?


-- 
Cheers,

David