linux-kernel - Re: [RFC PATCH] kmemleak: Scan all thread stacks

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Message-Id: <1247849826.6313.64.camel@pc1117.cambridge.arm.com>
Date:	Fri, 17 Jul 2009 17:57:06 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"Paul E. McKenney" <paulmck@...ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] kmemleak: Scan all thread stacks

On Fri, 2009-07-17 at 18:43 +0200, Ingo Molnar wrote:
> * Catalin Marinas <catalin.marinas@....com> wrote:
> > 2. Is it safe to use rcu_read_lock() and task_lock() when scanning the
> >    corresponding kernel stack (thread_info structure)? The loop doesn't
> >    do any modification to the task list. The reason for this is to
> >    allow kernel preemption when scanning the stacks.
> 
> you cannot generally preempt while holding the RCU read-lock.

This may work with rcupreempt enabled. But, with classic RCU is it safe
to call schedule (or cond_resched) while holding the RCU read-lock?

Thanks.

-- 
Catalin

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