Hey Steve, On Wed, Mar 15, 2023 at 4:28 PM Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > > On Wed, 15 Mar 2023 15:57:02 -0400 > Joel Fernandes <joel@xxxxxxxxxxxxxxxxx> wrote: > > > > I was going to suggest "kvfree_rcu_might_synchronize()" but that's just > > > getting ridiculous. > > > > No, synchronize() is incorrect. The code really can sleep for other > > reasons like memory allocation. It is not that simple of an > > implementation as one may imagine. mightsleep is really the correct > > wording IMHO. > > > > > Still, I will replace that code back to a kfree() and rcu_synchonize() than > > > to let that other name get in. > > > > I think it is too late for that for now, we already have conversions > > going into the other subsystems, that means we'll have to redo all > > that over again (even if it sounded like a good idea, which it is > > not). > > > > I would rather you just did: "#define kvfree_rcu_tracing > > #kvfree_rcu_mightsleep", or something like that, if it is really a > > problem. ;-) > > > > Also you are really the first person I know of who has a problem with that name. > > I guess you didn't read Jens's reply. Apologies, I am trying to keep up with email but this week is crazy. > The main issue I have with this, is that "might_sleep" is just an > implementation issue. It has *nothing* to do with what the call is about. > It is only about freeing something with RCU. It has nothing to do with > sleeping. I don't use it because it might sleep. I use it to free something. > > If you don't like kvfree_rcu_synchronization() then call it > kvfree_rcu_headless() and note that currently it can sleep. Because in > the future, if we come up with an implementation where we it doesn't sleep, > then we don't need to go and rename all the users in the future. > > See where I have the problem with the name "might_sleep"? I am doubtful there may be a future where it does not sleep. Why? Because you need an rcu_head *somewhere*. Unlike with debubojects, which involves a lock-free per-CPU pool and a locked global pool, and has the liberty to shutdown if it runs out of objects -- in RCU code it doesn't have that liberty and it has to just keep working. The kfree_rcu code does have pools of rcu_head as well, but that is not thought to be enough to prevent OOM when memory needs to be given back. AFAIK -- the synchronize_rcu() in there is a last resort and undesirable (supposed to happen only when running out of objects/memory). Also "mightsleep" means just that -- *might*. That covers the fact that sleeping may not happen ;-). This is just my opinion and I will defer to Uladzislau, Paul and you on how to proceed. Another option is "cansleep" which has the same number of characters as headless. I don't believe expecting users to read comments is practical, since we did already have comments and there was a bug in the usage that triggered this whole series. thanks, - Joel
