On Thu, Jun 21, 2018 at 01:27:12PM -0400, Alan Stern wrote: > More than one kernel developer has expressed the opinion that the LKMM > should enforce ordering of writes by release-acquire chains and by > locking. In other words, given the following code: > > WRITE_ONCE(x, 1); > spin_unlock(&s): > spin_lock(&s); > WRITE_ONCE(y, 1); > > or the following: > > smp_store_release(&x, 1); > r1 = smp_load_acquire(&x); // r1 = 1 > WRITE_ONCE(y, 1); > > the stores to x and y should be propagated in order to all other CPUs, > even though those other CPUs might not access the lock s or be part of > the release-acquire chain. In terms of the memory model, this means > that rel-rf-acq-po should be part of the cumul-fence relation. > > All the architectures supported by the Linux kernel (including RISC-V) > do behave this way, albeit for varying reasons. Therefore this patch > changes the model in accordance with the developers' wishes. > > Signed-off-by: Alan Stern <st...@rowland.harvard.edu>
Thanks for that Alan! Acked-by: Peter Zijlstra (Intel) <pet...@infradead.org>
