On Fri, Oct 9, 2020 at 4:14 PM Frederic Weisbecker <[email protected]> wrote: > > On Wed, Sep 23, 2020 at 11:22:08AM -0400, Joel Fernandes (Google) wrote: > > Currently, rcu_do_batch() depends on the unsegmented callback list's len > > field > > to know how many CBs are executed. This fields counts down from 0 as CBs are > > dequeued. It is possible that all CBs could not be run because of reaching > > limits in which case the remaining unexecuted callbacks are requeued in the > > CPU's segcblist. > > > > The number of callbacks that were not requeued are then the negative count > > (how > > many CBs were run) stored in the rcl->len which has been counting down on > > every > > dequeue. This negative count is then added to the per-cpu segmented callback > > list's to correct its count. > > > > Such a design works against future efforts to track the length of each > > segment > > of the segmented callback list. The reason is because > > rcu_segcblist_extract_done_cbs() will be populating the unsegmented callback > > list's length field (rcl->len) during extraction. > > Also, the design of counting down from 0 is confusing and error-prone IMHO. > > Right :)
:) > > This commit therefore explicitly counts have many callbacks were executed in > > s/have/how > > > rcu_do_batch() itself, and uses that to update the per-CPU segcb list's > > ->len > > field, without relying on the negativity of rcl->len. > > > > Signed-off-by: Joel Fernandes (Google) <[email protected]> > > Reviewed-by: Frederic Weisbecker <[email protected]> Thanks! Paul would be Ok to make the minor fixup s/have/how/ that Frederic pointed? - Joel (Due to COVID issues at home, I'm intermittently working so advance apologies for slow replies.)
