On mercoledì 7 dicembre 2022 14:51:00 CET Sebastian Andrzej Siewior wrote: > On 2022-12-07 14:01:50 [+0100], Fabio M. De Francesco wrote: > > > > If so, I understand and I again agree with you. If not, I'm missing > > > > something; so please let me understand properly. > > > > > > > > Aside from the above, I'm not sure whether you deleted the last phrase > > > > before > > > > your suggestion. What about making it to become "For the above- mentioned > > > > cases, conversions should also explicitly disable page-faults and/or > > > > preemption"? > > > > > > They need to disable preemption or page-faults or both if it is needed > > > (not unconditionally) and where it is needed. This means not > > > unconditionally over the whole kmap-ed section. > > > > I never meant to suggest to _unconditionally_ disable page-faults > > and/or preemption. I was only trying to say that developers must carefully > > check whether or not the whole kmap-ed section depended on those side > > effects. > I know. That are the two condition that should be checked/ kept in mind > while replacing the code. Maybe I read it wrongly… > > > If so, they must _explicitly_ disable preemption or page-faults or both > > together with the use of kmap_local_page(). > > Right. The requirement for it should be probably documented in case it > is not obvious. For PREEMPT_RT it will become a problem if the preempt > disabled section additionally acquired a spinlock_t or allocated memory. > So ideally it won't be used ;) > > > Instead, if the section doesn't > > > > depend on preemption and/or page-faults disabling, they must only replace > > kmap_atomic() with kmap_local_page(). > > Correct and I assumed that you know all this. > > > I had probably used a bad wording when trying to say the same things that > > you > > wrote much more clearly. > > Write it as you wish I just made a recommendation. If the wording is > crystal clear then there is less room for interpretations. I just sent v2 of this patch.[1] I hope that now I left less room for potential misinterpretation by merging your suggestion with the old text. Again thanks for helping, Fabio [1] https://lore.kernel.org/lkml/20221207225308.8290-1-fmdefrancesco@xxxxxxxxx/T/
