Messages in this thread | | | Date | Tue, 27 Feb 2007 12:25:17 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] adapt page_lock_anon_vma() to PREEMPT_RCU |
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> On Sun, 25 Feb 2007 23:06:21 +0300 Oleg Nesterov <oleg@tv-sign.ru> wrote: > page_lock_anon_vma() uses spin_lock() to block RCU. This doesn't work with > PREEMPT_RCU, we have to do rcu_read_lock() explicitely. Otherwise, it is > theoretically possible that slab returns anon_vma's memory to the system > before we do spin_unlock(&anon_vma->lock). > > ... > > +static void page_unlock_anon_vma(struct anon_vma *anon_vma) > +{ > + spin_unlock(&anon_vma->lock); > + rcu_read_unlock(); > }
It's a bit sad doing a double preempt_disable() for non-PREEMPT_RCU builds.
Perhaps we would benefit from a new rcu_read_lock_preempt_rcu() which is a no-op if !PREEMPT_RCU.
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