On 04/25/2011 09:48 PM, Paul E. McKenney wrote: > On Mon, Apr 25, 2011 at 04:20:37PM +0800, Lai Jiangshan wrote: >> I read the code and comments written by Nick Piggin(mainly from e286781d), >> page_cache_get_speculative() is protected by rcu_read_lock(), >> it may be preempted when preemptible RCU, so we must use >> get_page_unless_zero() >> in this situation. >> >> In the days of e286781d, we only have CLASSIC_RCU and (old)PREEMPT_RCU, >> so "defined(CONFIG_CLASSIC_RCU)" means non-preemptible RCU and the code is >> correct. >> >> In the days of b560d8ad, we only have TREE_RCU and TREE_PREEMPT_RCU, >> so "defined(CONFIG_TREE_RCU)" means non-preemptible RCU and the code is >> correct. >> >> But in nowadays, we have TREE_RCU, TREE_PREEMPT_RCU, TINY_RCU and >> TINY_PREEMPT_RCU, >> so the "defined(CONFIG_TREE_RCU)" for non-preemptible RCU is incorrect, and >> it may causes bugs. >> we should use "!defined(CONFIG_PREEMPT_RCU)" for non-preemptible RCU code >> block. >> >> CC: Nick Piggin <[email protected]> >> Cc: Paul E. McKenney <[email protected]> >> Reported-by: WANG Cong <[email protected]> >> Signed-off-by: Lai Jiangshan <[email protected]> > > Good catch!!! > > Acked-by: Paul E. McKenney <[email protected]> >
Sorry, I forgot to CC it to LKML. Added it. Hi, Nick Piggin, Could you review it? Thanks, Lai _______________________________________________ stable mailing list [email protected] http://linux.kernel.org/mailman/listinfo/stable
