On Mon, Nov 25, 2019 at 04:46:25PM -0500, Steven Rostedt wrote: > On Mon, 25 Nov 2019 12:37:09 -0500 > Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > > > On Sun, 24 Nov 2019 23:38:41 -0500 > > "Frank A. Cancio Bello" <frank@xxxxxxxxxxxxxxxxxxxxxx> wrote: > > > > > --- a/Documentation/trace/ring-buffer-design.txt > > > +++ b/Documentation/trace/ring-buffer-design.txt > > > @@ -37,7 +37,7 @@ commit_page - a pointer to the page with the last finished non-nested write. > > > > > > cmpxchg - hardware-assisted atomic transaction that performs the following: > > > > > > - A = B iff previous A == C > > > + A = B if previous A == C > > > > This wasn't a typo. "iff" means "if and only if" which is a standard > > notation. That is, this is shorthand for: > > > > A = B if previous A == C > > previous A == C if A = B > > Although thinking about this more, this may not be correct. If > previous A == B, then A = B, thus the "iff" notation is not actually > accurate. > > This wouldn't then be a typo fix, but a real fix to the logic ;-) > What are the odds ;) I knew about the concept https://en.wikipedia.org/wiki/If_and_only_if from school math but didn't remember the notation. For me was suspicious so, I looked in "the cmpxchg doc" and nothing referring to "iff" was there, then I decided to classified it as a typo. Now thinking more deeply, I agreed with you that was not a typo but a "logic mistake", even not for the same reason ;) Being not 100% sure of what I'm about to say, I will say it anyway because you have been kind enough to write the second email. "if and only if (shortened as iff) is a biconditional logical connective between statements" and A = B can't be considered a logical statement in the context of that definition (math/logic), even it could be in C. Thank you Steven one more time for such a quick reply! frank a.
