* Andrea Parri <andrea.parri@xxxxxxxxxxxxxxxxxxxx> wrote: > On Wed, Apr 04, 2018 at 06:56:32AM +0200, Ingo Molnar wrote: > > > > * Andrea Parri <andrea.parri@xxxxxxxxxxxxxxxxxxxx> wrote: > > > > > In Ingo's words [1]: > > > > > > "[...] what should be done instead is to write a script that refreshes > > > all the arch-support.txt files in-place. [...] > > > > > > It's OK for the script to have various quirks for weirdly implemented > > > features and exceptions: i.e. basically whenever it gets a feature wrong, > > > we can just tweak the script with quirks to make it all work out of box. > > > > > > [...] But in the end there should only be a single new script: > > > > > > Documentation/features/scripts/features-refresh.sh > > > > > > ... which operates on the arch-support.txt files and refreshes them in > > > place, and which, after all the refreshes have been committed, should > > > produce an empty 'git diff' result." > > > > > > "[...] New features can then be added by basically just creating a > > > header-only arch-support.txt file, such as: > > > > > > triton:~/tip/Documentation/features> cat foo/bar/arch-support.txt > > > # > > > # Feature name: shiny new fubar kernel feature > > > # Kconfig: ARCH_USE_FUBAR > > > # description: arch supports the fubar feature > > > # > > > > > > And running Documentation/features/scripts/features-refresh.sh would > > > auto-generate the arch support matrix. [...] > > > > > > This way we soft- decouple the refreshing of the entries from the > > > introduction of the features, while still making it all easy to keep > > > sync and to extend." > > > > > > This RFC presents a first attempt to implement such a feature/script, and > > > applies it script on top of Arnd's: > > > > > > git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic.git arch-removal > > > > > > Patch 1/3 provides the "features-refresh.sh" script. Patch 2/3 removes the > > > "BPF-JIT" feature file and it creates header-only files for "cBPF-JIT" and > > > "eBPF-JIT". Patch 3/3 presents the results of running the script; this run > > > also printed to standard output the following warnings: > > > > > > WARNING: '__HAVE_ARCH_STRNCASECMP' is not a valid Kconfig > > > WARNING: 'Optimized asm/rwsem.h' is not a valid Kconfig > > > WARNING: '!ARCH_USES_GETTIMEOFFSET' is not a valid Kconfig > > > WARNING: '__HAVE_ARCH_PTE_SPECIAL' is not a valid Kconfig > > > > > > (I'm sending these patches with empty commit messagges, for early feedback: > > > I'll fill in these messages in subsequent versions if this makes sense...) > > > > > > Cheers, > > > Andrea > > > > > > Andrea Parri (3): > > > Documentation/features: Add script that refreshes the arch support status files in place > > > Documentation/features/core: Add arch support status files for 'cBPF-JIT' and 'eBPF-JIT' > > > Documentation/features: Refresh and auto-generate the arch support status files in place > > > > Ok, this series is really impressive at its RFC stage already! > > > > Beyond fixing those warnings, I'd also suggest another change: please make the > > new BPF features patch the last one, so that the 'refresh' patch shows how much > > original bit-rot we gathered recently. > > > > The 'new features' patch should then also include the result of also running the > > script, i.e. a single patch adding the base fields and the generated parts as > > well. That will be the usual development flow anyway - people won't do two-part > > patches just to show which bits are by hand and which are auto-generated. > > Yes, I'll do. > > Let me ask some hints about the warnings, as I'm not sure how to 'fix' them; > we have: > > a) __HAVE_ARCH_STRNCASECMP > __HAVE_ARCH_PTE_SPECIAL > > b) Optimized asm/rwsem.h > > c) !ARCH_USES_GETTIMEOFFSET > > For (c), I see two options: > > 1. replace that with 'ARCH_USES_GETTIMEOFFSET' (and update the status > matrix accordingly) > > 2. add logics/code to the script to handle simple boolean expressions > (mmh, this could get nasty really soon... let's say: limiting to a > leading '!', to start with ;) Yeah, so the problem here is that the feature is the _lack_ of legacy ARCH_USES_GETTIMEOFFSET, so we cannot just invert the check - the output would be rather confusing ... Negating the switch in the kernel would force us to add a "arch uses modern timekeeping" flag to every other architecture - not a very good solution. I'd suggest adding support for a simple '!' operator with very strict syntax - nothing more. (This would also be useful for (b), see below.) > For (a), I realize that 'grep-ing' the macros in arch-specific _sources_ > does serve the purpose of producing the hard-coded status matrices; but > is this a reasonable approach? (e.g., can produce 'false-positives'?) I'd suggest removing both :-) - strncasecmp() is an insignificant API and no arch has optimized it so far. - __HAVE_ARCH_PTE_SPECIAL is really a hardware detail. > What could it be a suitable solution for (b)? are there Kconfig options > which I could in place of that expression? some other suggestion? Yes, !RWSEM_GENERIC_SPINLOCK expresses this equivalently. If you implement the NOT operator for ARCH_USES_GETTIMEOFFSET then it would handle this one as well. Thanks, Ingo
