On Mon, 2018-04-09 at 16:23 +1000, Nicholas Piggin wrote: > On Mon, 09 Apr 2018 15:57:55 +1000 > Benjamin Herrenschmidt <b...@kernel.crashing.org> wrote: > > > On Mon, 2018-04-09 at 15:40 +1000, Nicholas Piggin wrote: > > > The RAW console does not need writes to be atomic, so implement a > > > _nonatomic variant which does not take a spinlock. This API is used > > > in xmon, so the less locking thta's used, the better chance there is > > > that a crash can be debugged. > > > > I find the term "nonatomic" confusing... > > I guess it is to go with the "atomic" comment for the hvsi console > case -- all characters must get to the console together or not at > all.
Yeah ok, it's just that in Linux "atomic" usually means something else :-) Why not just call it "unlocked" which is what it's about and matches existing practices thorough the kernel ? > > don't we have a problem if we > > start hitting OPAL without a lock where we can't trust > > opal_console_write_buffer_space anymore ? I think we need to handle > > partial writes in that case. Maybe we should return how much was > > written and leave the caller to deal with it. > > Yes, the _nonatomic variant doesn't use opal_console_write_buffer_space > and it does handle partial writes by returning written bytes (although > callers generally tend to loop at the moment, we might do something > smarter with them later). > > > I was hoping (but that isn't the case) that by nonatomic you actually > > meant calls that could be done in a non-atomic context, where we can do > > msleep instead of mdelay. That would be handy for the console coming > > from the hvc thread (the tty one). > > Ah right, no. However we no longer loop until everything is written, so > the hvc console driver (or the console layer) should be able to deal with > that with sleeping. I don't think we need to put it at this level of the > driver, but I don't know much about the console code. Ok, so hopefully we shouldn't be hitting the delay.. Cheers, Ben.
