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A question about the notification in Mach

From: Da Zheng
Subject: A question about the notification in Mach
Date: Mon, 01 Jun 2009 08:12:28 +0800
User-agent: Thunderbird (Macintosh/20090302)


All the notification RPCs (in notify.defs) are simple routines, i.e., the client (the kernel) doesn't expect the replies.
Then what is the meaning of the return values of their server code?
Take the function below as an example (it is in proc/notify.c).

If the task port becomes a dead name, the function returns 0; otherwise, it return EINVAL. If the kernel doesn't care the return value, why does do_mach_notify_dead_name handler return different values?

Thank you,
Zheng Da

do_mach_notify_dead_name (mach_port_t notify,
                         mach_port_t deadport)
 struct proc *p;

 /* Drop gratuitous extra reference that the notification creates. */
 mach_port_deallocate (mach_task_self (), deadport);

 if (notify == generic_port)
     check_dead_execdata_notify (deadport);
     return 0;

 p = ports_lookup_port (proc_bucket, notify, proc_class);

 if (!p)
   return EOPNOTSUPP;

 if (p->p_task == deadport)
     process_has_exited (p);
     ports_port_deref (p);
     return 0;
     ports_port_deref (p);
     return EINVAL;

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