Re: [2.6.33-rc5] starting emacs makes lockdep warning

From: KOSAKI Motohiro
Date: Tue Jan 26 2010 - 02:45:56 EST


> On Tue, Jan 26, 2010 at 02:01:12PM +0800, Am??rico Wang wrote:
> > I agree, it seems that patch is useless, since we already
> > do lock_kernel() before calling __f_setown()...
> What's to prevent pid from being freed under us? BKL won't...

I don't understand this issue at all. so, this is stupid dumb question.
Why can't we write following code?

enum pid_type type;
struct pid *pid;
if (!waitqueue_active(&tty->read_wait))
tty->minimum_to_wake = 1;
spin_lock_irqsave(&tty->ctrl_lock, flags);
if (tty->pgrp) {
pid = tty->pgrp;
} else {
pid = task_pid(current);
get_pid(pid) // insert here
spin_unlock_irqrestore(&tty->ctrl_lock, flags);
retval = __f_setown(filp, pid, type, 0);
put_pid(pid) // insert here

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