On Wed, 2017-10-04 at 09:06 +0200, Christoph Hellwig wrote: > > + /* > > + * Ensure that the effect of blk_set_preempt_only() is globally > > + * visible before unfreezing the queue. > > + */ > > + if (err == 0) > > + synchronize_rcu(); > > I don't understand why we'd need this. The flag is set both under > a spinlock and a mutex that are unlocked right after. That should > gurantee all the visibility we'll need. Hello Christoph, That synchronize_rcu() call follows the example in the third figure in https://lwn.net/Articles/573497/. I will verify whether that synchronize_rcu() call can be left out. Bart.
