On Tue, 2017-05-30 at 08:22 +0800, Ming Lei wrote: > On Sun, May 28, 2017 at 04:10:09PM +0000, Bart Van Assche wrote: > > I really would like to see the blk_queue_quiesced() tests as close as > > possible to > > the blk_mq_hctx_stopped() tests. But I agree that we need a way to document > > and/or > > Could you explain why we have to do that? And checking on stopped state > doesn't need to hold RCU/SRCU read lock, and that two states are really > different.
I'm really surprised that you ask me why ... It's because the purpose of the "stopped" and "quiesced" flags is similar, namely preventing that dispatching requests happens. It doesn't matter that with your patches applied it is no longer needed to hold an RCU / SRCU lock when testing the stopped flag. > > verify that these tests occur with an RCU read-side lock held. Have you > > considered > > to use rcu_read_lock_held() to document this? > > Then we need to check if it is RCU or SRCU, and make code ugly as > current check on BLOCKING. How about introducing a macro or inline function in the block layer that tests whether either the RCU read lock or an SRCU read lock is held depending on the value of the BLK_MQ_F_BLOCKING flag? Bart.
