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

Jens Axboe
2021-03-26T15:52:44Z

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.

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);
}

/*
--
2.31.0