Re: [PATCH] fix tasklist + find_pid() with CONFIG_PREEMPT_RCU

[Ingo Molnar]

* Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:

> On Tue, 29 Jan 2008 19:40:19 +0300
> Oleg Nesterov <oleg@xxxxxxxxxx> wrote:
> 
> > With CONFIG_PREEMPT_RCU read_lock(tasklist_lock) doesn't imply 
> > rcu_read_lock(),
> 
> I'm suspecting that we have other code which assumes that read_lock, 
> write_lock and spin_lock imply rcu_read_lock().
> 
> I wonder if there are any sane runtime checks we can put in there to 
> find such problems.

we usually caught them via the DEBUG_PREEMPT checks on PREEMPT_RT: stuff 
that has such implicit reliance tends to use smp_processor_id() along 
the way and that gets flagged if the non-preemptability guarantee of 
spin_lock() vanishes.

	Ingo
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