Date: Tue, 27 Jan 2009 14:26:26 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Mandeep Singh Baines <msb@google.com>
Cc: linux-kernel@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>,
       =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker <fweisbec@gmail.com>,
       rientjes@google.com, mbligh@google.com, thockin@google.com,
       Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v4] softlockup: remove hung_task_check_count
Message-ID: <20090127132626.GH23121@elte.hu>
References: <1232991701.4863.222.camel@laptop> <20090127003055.GA21269@google.com>
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* Mandeep Singh Baines <msb@google.com> wrote:

> The design was proposed by Fr?d?ric Weisbecker. Peter Zijlstra suggested 
> the use of RCU.

ok, this looks _much_ cleaner.

One question:

> -	read_lock(&tasklist_lock);
> +	rcu_read_lock();
>  	do_each_thread(g, t) {
> -		if (!--max_count)
> +		if (need_resched())
>  			goto unlock;

Isnt it dangerous to skip a check just because we got marked for 
reschedule? Since it runs so rarely it could by accident be preempted and 
we'd not get any checking done for a long time.

	Ingo
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