Re: [PATCH 3/7] kernel: stop masking signals in create_io_thread()

Eric W. Biederman
2021-03-26T20:46:30Z

Jens Axboe <axboe@kernel.dk> writes:

> This is racy - move the blocking into when the task is created and
> we're marking it as PF_IO_WORKER anyway. The IO threads are now
> prepared to handle signals like SIGSTOP as well, so clear that from
> the mask to allow proper stopping of IO threads.

Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>

>
> Reported-by: Oleg Nesterov <oleg@redhat.com>
> Signed-off-by: Jens Axboe <axboe@kernel.dk>
> ---
> kernel/fork.c | 16 ++++++++--------
> 1 file changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/kernel/fork.c b/kernel/fork.c
> index d3171e8e88e5..ddaa15227071 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -1940,8 +1940,14 @@ static __latent_entropy struct task_struct *copy_process(
> p = dup_task_struct(current, node);
> if (!p)
> goto fork_out;
> - if (args->io_thread)
> + if (args->io_thread) {
> + /*
> + * Mark us an IO worker, and block any signal that isn't
> + * fatal or STOP
> + */
> p->flags |= PF_IO_WORKER;
> + siginitsetinv(&p->blocked, sigmask(SIGKILL)|sigmask(SIGSTOP));
> + }
>
> /*
> * This _must_ happen before we call free_task(), i.e. before we jump
> @@ -2430,14 +2436,8 @@ struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node)
> .stack_size = (unsigned long)arg,
> .io_thread = 1,
> };
> - struct task_struct *tsk;
>
> - tsk = copy_process(NULL, 0, node, &args);
> - if (!IS_ERR(tsk)) {
> - sigfillset(&tsk->blocked);
> - sigdelsetmask(&tsk->blocked, sigmask(SIGKILL));
> - }
> - return tsk;
> + return copy_process(NULL, 0, node, &args);
> }
>
> /*