Messages in this thread | | | Date | Tue, 15 Oct 2019 16:43:57 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 1/2] pidfd: verify task is alive when printing fdinfo |
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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.
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