Messages in this thread | | | Date | Fri, 27 Jun 2008 14:00:40 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH 4/5 v2] x86 boot: show pfn addresses in hex not decimal in some kernel info printks |
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* Sam Ravnborg <sam@ravnborg.org> wrote:
> Hi Ingo > > > Sparse is a cool tool that extends upon C types (and more), but it's > > been made too hard to use widely: > > > > - right now it's opt-in with no ability for testers to use it > > transparently while also building the kernel. Forcing a second > > kernel build just for 'debugging' reduces the userbase. > > This is waht make C=1 is for. If this is broken then we should > fix it. > Just trying it out: > $ make C=1 kernel/sched.o > CHECK kernel/sched.c > kernel/sched_fair.c:37:14: warning: symbol 'sysctl_sched_latency' was not declar ed. Should it be static? > kernel/sched_fair.c:43:14: warning: symbol 'sysctl_sched_min_granularity' was no t declared. Should it be static? > kernel/sched_fair.c:72:14: warning: symbol 'sysctl_sched_wakeup_granularity' was not declared. Should it be static? > ... > CC kernel/sched.o > > > So make C=1 works as intended and let you run sparse on the files that > are built - and only those.
ah, ok - i was confused about that.
> > Fortunately these problems are all solvable gradually: > > > > - a kbuild mechanism to get _parallel_ Sparse checks. I.e. both the > > real .o gets produced but also the "make C=1" output is produced. > > Testers would be enabled to do Sparse checks "alongside" of a normal > > kernel build. (Sparse is plenty fast for this to be practical) > Already present. > > > > > - kbuild mechanism with which subsystem maintainers could mark specific > > files (or all of their subdirectories) of their subsystem as to be > > Sparse-checked by default. [if a .config debug option is enabled] > > For example we'd mark all of arch/x86/*.o and kernel/sched*.o in such > > a way for example. > That would then be on a directory basis. > You can do: > diff --git a/kernel/Makefile b/kernel/Makefile > index 1c9938a..1ba00aa 100644 > --- a/kernel/Makefile > +++ b/kernel/Makefile > @@ -2,6 +2,7 @@ > # Makefile for the linux kernel. > # > > +KBUILD_CHECKSRC=1 > obj-y = sched.o fork.o exec_domain.o panic.o printk.o profile.o \ > exit.o itimer.o time.o softirq.o resource.o \ > sysctl.o capability.o ptrace.o timer.o user.o \ > > already today. > It applies recursively so we will then run sparse on kernel/time/*.o too. > > There is no easy way to cover all of arch/x86/*.o as the files are distributed > in several Makefiles and there is no common one. > > > > > - a second layer would be very useful as well: failures would turn into > > build failures if a debug .config switch is enabled. > This could be a simple: > ifdef CONFIG_CHECK_IS_ERROR > CHECKFLAGS += -Werror > endif > > And teach sparse about -Werror > > > On a similar note, it would be nice if subsystem maintainers had a > > kbuild mechanism to have the fails they maintain to be built via -Werr > > (if an opt-in .config option is enabled). > > For each Makefile (does not apply recursively): > ccflags-$(CONFIG_PROMOTE_WARNINGS_TO_ERROR) += -Werror > > When I get around to it: > ccflags-sched.o-$(CONFIG_PROMOTE_WARNINGS_TO_ERROR) += -Werror
if there's a generic kbuild facility for it i'd love to try something like that out, on files that i maintain. There should perhaps be a shortcut for it? Something like:
ccflags-sched.o += -Werror
and kbuild would decide whether CONFIG_PROMOTE_WARNINGS_TO_ERROR is set and whether to filter out -Werror or not?
Ingo
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