On Wed, Apr 27, 2011 at 12:03 PM, Lai Jiangshan <[email protected]> wrote: > 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. >
Thanks for fixing this! The description explains quite well, so I am okay with this patch, Reviewed-by: WANG Cong <[email protected]> BTW, you added my company email in Reported-by, but Cc'ed my gmail. ;-) _______________________________________________ stable mailing list [email protected] http://linux.kernel.org/mailman/listinfo/stable
