On 10/04, Peter Zijlstra wrote: > > On Thu, Oct 03, 2013 at 11:10:09PM +0200, Oleg Nesterov wrote: > > On 10/03, Oleg Nesterov wrote: > > > > > > So unless Peter objects I'll write the changelogs (always nontrivial > > > task), > > > test, and send these 2 patches + "add ops->barr() / rcu_sync_wait_for_cb" > > > tomorrow. > > > > And, can't resist, probably another patch below (incomplete, needs the > > obvious change in cpu.c and the new trivial __complete_locked() helper). > > > > Hmm. But when I look at wait_for_completion() I think it is buggy.
No, sorry for noise, it is fine. > > rcusync: introduce rcu_sync_struct->exclusive mode > > What's exclusive to mean? One writer at a time? Yes, > Why don't use use the > waitqueue in exclusive mode and use a single wake_up instead of > wake_up_all()? But this won't work, wait_event_exclusive(wq, CONDITION)-like code obviously can't guarantee that only a single thread sees CONDITION, even if "unlock" does __wake_up(nr_exclusive => 1). Of course we can fix this, but wait_for_completion/complete already does the necessary work: x->done acts as a resource counter which is always checked/incremented/decremented under the same lock. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
