Re: [PATCH 1/2] pidfd: verify task is alive when printing fdinfo

On 10/15, Christian Brauner wrote:

+static inline bool task_alive(struct pid *pid) +{

• bool alive = true;
• rcu_read_lock();
• if (!pid_task(pid, PIDTYPE_PID))

• alive = false;
  

• rcu_read_unlock();
• return alive;

+}

Well, the usage of rcu_read_lock/unlock looks confusing to me...

I mean, this helper does not need rcu lock at all. Except rcu_dereference_check() will complain.

static inline bool task_alive(struct pid *pid) { bool alive;

/* shut up rcu_dereference_check() */ rcu_lock_acquire(&rcu_lock_map); alive = !!pid_task(pid, PIDTYPE_PID)); rcu_lock_release(&rcu_lock_map);

return alive; }

looks more clear imo.

But in fact I'd suggest to simply use !hlist_empty(&pid->tasks[PIDTYPE_PID]) in pidfd_show_fdinfo() and do not add a new helper.

Oleg.