Re: [RFC PATCH] kmemleak: Scan all thread stacks

Peter Zijlstra
2009-07-17T17:01:28Z

On Fri, 2009-07-17 at 17:57 +0100, Catalin Marinas wrote:
> On Fri, 2009-07-17 at 18:43 +0200, Ingo Molnar wrote:
> > * Catalin Marinas <catalin.marinas@arm.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?

No.