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Date: Wed, 29 Jun 2016 09:15:52 -0400
From: Tejun Heo <tj@kernel.org>
To: Petr Mladek <pmladek@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Oleg Nesterov <oleg@redhat.com>, Ingo Molnar <mingo@redhat.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Josh Triplett <josh@joshtriplett.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Jiri Kosina <jkosina@suse.cz>, Borislav Petkov <bp@suse.de>,
        Michal Hocko <mhocko@suse.cz>, linux-mm@kvack.org,
        Vlastimil Babka <vbabka@suse.cz>, linux-api@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v9 06/12] kthread: Add kthread_drain_worker()
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Hello,

On Wed, Jun 29, 2016 at 10:17:48AM +0200, Petr Mladek wrote:
> > Ah, okay, I don't think we need to change this.  I was suggesting to
> > simplify it by dropping the draining and just do flush from destroy.
> 
> I see. But then it does not address the original concern from Peter
> Zijlstra. He did not like that the caller was responsible for blocking
> further queueing. It still will be needed. Or did I miss something,
> please?

You can only protect against so much.  Let's say we make the worker
struct to be allocated by the user, what then prevents it prematurely
from user side?  Use-after-free is use-after-free.  If we can trivally
add some protection against it, great, but no need to contort the
design to add marginal protection.

Thanks.

-- 
tejun