Subject: Re: more efficient current_is_keventd macro? [was Re: [lhcs-devel]
	Re: Kthread_create() never returns when called from worker_thread]
From: Rusty Russell <rusty@rustcorp.com.au>
To: Andrew Morton <akpm@osdl.org>
Cc: vatsa@in.ibm.com, mingo@redhat.com, linux-kernel@vger.kernel.org
In-Reply-To: <20040308143658.25c1d378.akpm@osdl.org>
References: <20040308123030.GA7428@in.ibm.com>
	 <20040308143658.25c1d378.akpm@osdl.org>
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Message-Id: <1078797038.18171.707.camel@bach>
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Date: Tue, 09 Mar 2004 12:50:39 +1100
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On Tue, 2004-03-09 at 09:36, Andrew Morton wrote:
> Srivatsa Vaddagiri <vatsa@in.ibm.com> wrote:
> > int current_is_keventd(void)
> > {
> > +       int cpu = smp_processor_id();
> > +	cwq = keventd_wq->cpu_wq + cpu;
> > +	if (current == cwq->thread)
> > +		return 1;
> > +	else
> > +		return 0;
> > }
> 
> Is racy in the presence of preemption.

Actually, it's not, because if current *is* keventd we're nailed to the
CPU, and if it's not, we're going to return false either way.

But it *should* be fixed, simply as an example to others.

Cheers,
Rusty.
-- 
Anyone who quotes me in their signature is an idiot -- Rusty Russell

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