From mboxrd@z Thu Jan  1 00:00:00 1970
From: joel@joelfernandes.org (Joel Fernandes)
Date: Mon, 29 Apr 2019 10:07:43 -0400
Subject: [PATCH v1 1/2] Add polling support to pidfd
In-Reply-To: <20190429140245.GB233442@google.com>
References: <20190425190010.46489-1-joel@joelfernandes.org>
 <20190425222359.sqhboc4x4daznr6r@brauner.io>
 <20190428162405.GA6757@redhat.com>
 <20190429140245.GB233442@google.com>
Message-ID: <20190429140743.GB173743@google.com>
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Message-ID: <20190429140743.HcI12Re6p2r7NQqRblh3WVz3p6UNEGbjQ2YdmdlZB0E@z>

On Mon, Apr 29, 2019@10:02:45AM -0400, Joel Fernandes wrote:
> On Sun, Apr 28, 2019@06:24:06PM +0200, Oleg Nesterov wrote:
[snip]
> > > > +{
> > > > +	struct pid *pid;
> > > > +
> > > > +	lockdep_assert_held(&tasklist_lock);
> > > > +
> > > > +	pid = get_task_pid(task, PIDTYPE_PID);
> > > > +	wake_up_all(&pid->wait_pidfd);
> > > > +	put_pid(pid);
> > 
> > Why get/put?
> 
> Yes, pid_task() should do it. Will update it. Thanks!

I spoke too soon. We need the task's pid of type PIDTYPE_PID. How else can we
get it? This does an atomic_inc on the pid->count, so we need to put_pid()
after we are done with it. Did I miss something?

thanks,

 - Joel