Re: while_each_thread() under rcu_read_lock() is broken?

[Roland McGrath]

> We can't do call_rcu(release_task),
> we can't take tasklist for writing in the softirq context. But even
> if we could, this can't help in fact or I missed something.

Ah, I had missed that constraint of call_rcu.  (It's not mentioned in the
kerneldoc comment directly, and is only buried in a couple of brief
mentions in Documentation/RCU/.)  I was thinking that would suffice because
it does it between rcu_read_lock critical sections, but I guess it actually
only does it after the last one and doesn't prevent a new one from having
started on another CPU.  (And we can't use it anyway.)


Thanks,
Roland
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