On Tue, Mar 31, 2020 at 02:11:54PM +0100, Will Deacon wrote: > On Mon, Mar 30, 2020 at 04:25:05PM -0700, Paul E. McKenney wrote: > > On Tue, Mar 24, 2020 at 03:36:30PM +0000, Will Deacon wrote: > > > This reverts commit 2f073848c3cc8aff2655ab7c46d8c0de90cf4e50. > > > > > > There is no need to use WRITE_ONCE() to initialise a non-RCU 'list_head'. > > > > > > Cc: Paul E. McKenney <paulmck@xxxxxxxxxx> > > > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > > > Signed-off-by: Will Deacon <will@xxxxxxxxxx> > > > > And attention to lockless uses of list_empty() here, correct? > > > > Depending on the outcome of discussions on 3/21, I should have added in > > all three cases. > > Yes, patch 3 is where this will get sorted. It looks like we'll have to > disable KCSAN around the READ_ONCE() over there, but I also need to finish > wrapping my head around list_empty_careful() because I'm deeply suspicious! At the very least, it does have the disadvantage of touching an additional cache line, and up to two additional cache lines in the non-empty case. :-( Thanx, Paul
