On Mon, May 24, 2021 at 12:24:00PM +0800, Xiongwei Song wrote: > On Fri, May 21, 2021 at 11:17 PM Waiman Long <llong@xxxxxxxxxx> wrote: > > > > On 5/21/21 2:29 AM, Xiongwei Song wrote: > > > From: Xiongwei Song <sxwjean@xxxxxxxxx> > > > > > > The block condition matrix is using 'E' as the writer noation here, so it > > > would be better to use 'E' as the reminder rather than 'W'. > > > > > > Signed-off-by: Xiongwei Song <sxwjean@xxxxxxxxx> > > > --- > > > Documentation/locking/lockdep-design.rst | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/Documentation/locking/lockdep-design.rst b/Documentation/locking/lockdep-design.rst > > > index 9f3cfca..c3b923a 100644 > > > --- a/Documentation/locking/lockdep-design.rst > > > +++ b/Documentation/locking/lockdep-design.rst > > > @@ -462,7 +462,7 @@ Block condition matrix, Y means the row blocks the column, and N means otherwise > > > | R | Y | Y | N | > > > +---+---+---+---+ > > > > > > - (W: writers, r: non-recursive readers, R: recursive readers) > > > + (E: writers, r: non-recursive readers, R: recursive readers) > > > > > > > > > acquired recursively. Unlike non-recursive read locks, recursive read locks > > > > I would say it should be the other way around. Both W and E refer to the > > same type of lockers. W emphasizes writer aspect of it and E for > > exclusive. I think we should change the block condition matrix to use W > > instead of E. > > The doc uses 'E' to describe dependency egdes too. Should we change them > to 'W'? Personally, both 'W' and 'E' are fine. > I also think Waiman's suggestion is solid, there are two ways to classify locks: 1. W (Writers), R (Recursive Readers), r (Non-recursive Readers) 2. E (Exclusive locks), S (Shared locks), R (Recursive Readers), N (Non-recursive locks) And the relations between them are as follow: E = W R = R N = W \/ r S = R \/ r , where "\/" is the set union. The story is that I used the way #1 at first, and later on realized way #2 is better for BFS implementation, also for reasoning, so here came this leftover.. If you are interested, go ahead sending a patch fixing this, otherwise, I will fix this. Regards, Boqun > Thanks, > Xiongwei > > > > Cheers, > > Longman > >
