On Thu, Jun 08, 2017 at 04:47:43PM -0700, Paul E. McKenney wrote: > On Thu, Jun 08, 2017 at 02:28:14PM -0700, Krister Johansen wrote: > > On Thu, Jun 08, 2017 at 01:55:00PM -0700, Paul E. McKenney wrote: > > > Interesting! This is the first that I have heard that this was anything > > > other than a theoretical bug. To the comment in your second URL, it is > > > wise to recall that a seismologist was in fact arrested for failing to > > > predict an earthquake. Later acquitted/pardoned/whatever, but arrested > > > nonetheless. ;-) > > > > Point taken. I do realize that we all make mistakes, and certainly I do > > too. > > Indeed! Let's just say that the author of that email will have no > trouble returning the favor, and sooner rather than later. ;-) No doubt he's polishing up an extra small extra tight pair of handcuffs with my name on them. > > Perhaps I should have said that my survey of current callers of > > swake_up() was enough to convince me that I didn't have an immediate > > problem elsewhere, but that I'm not familiar enough with the code base > > to make that statement with a lot of authority. The concern being that if > > the patch came from RT-linux where the barrier was present in > > swake_up(), are there other places where swake_up() callers still assume > > this is being handled on their behalf? > > > > As part of this, I also pondered whether I should add a comment around > > swake_up(), similar to what's already there for waitqueue_active. > > I wasn't sure how subtle this is for other consumers, though. > > In my case, I assume I need barriers for swake_up(), which is why I > found this bug by inspection. Still, I wouldn't mind a comment. > Others might have other opinions. Since you don't mind, I've prepared a small patch for those comments. I'll send that in a separate thread. Thanks again, -K