On Sat, 5 Mar 2016, Michal Marek wrote: > On Fri, Mar 04, 2016 at 11:53:53PM +0100, Michal Marek wrote: > > Dne 4.3.2016 v 23:51 Michal Marek napsal(a): > > > Dne 4.3.2016 v 06:40 Nicolas Pitre napsal(a): > > >> +cmd_and_fixdep = > > >> \ > > >> + $(echo-cmd) $(cmd_$(1)); > > >> \ > > >> + $(ksym_dep_filter) | > > >> \ > > >> + scripts/basic/fixdep -e $(depfile) $@ '$(make-cmd)' > > >> \ > > >> + > $(dot-target).tmp; > > >> \ > > >> + rm -f $(depfile); > > >> \ > > >> + mv -f $(dot-target).tmp $(dot-target).cmd; > > > > > > While trying this, I got a SIGBUS from fixdep once. My theory is that > > > the depfile is mmap()ed by fixdep and modified by the preprocesor run at > > > the same time. I could not reproduce this so far (still trying). But if > > > it's really this race, the fix would be to disable dependency generation > > > in the preprocessor by passing -Wp,MD,/dev/null or somesuch. But we > > > never had this problem with genksyms, which is weird. It could as well > > > be that my build machine's memory is faulty :(. > > > > Actually, genksyms does not ran in parallel. neither before nor after > run > > this patch. > > I reproduced the SIGBUS after a few iterations, and it crashes in > parse_dep_file(). I'm now testing this > > diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include > index 0be7e09ba381..4fdd8348acf6 100644 > --- a/scripts/Kbuild.include > +++ b/scripts/Kbuild.include > @@ -270,10 +270,12 @@ else > > # Filter out exported kernel symbol names from the preprocessor output. > # See also __KSYM_DEPS__ in include/linux/export.h. > +# We disable the depfile generation here, so as not to overwrite the existing > +# depfile while fixdep is parsing it > ksym_dep_filter = > \ > case "$(1)" in \ > - cc_*_c) $(CPP) $(c_flags) -D__KSYM_DEPS__ $< ;; \ > - as_*_S) $(CPP) $(a_flags) -D__KSYM_DEPS__ $< ;; \ > + cc_*_c) $(CPP) $(filter-out -Wp$(comma)-M%, $(c_flags)) -D__KSYM_DEPS__ > $< ;; \ > + as_*_S) $(CPP) $(filter-out -Wp$(comma)-M%, $(a_flags)) -D__KSYM_DEPS__ > $< ;; \ > cpp_lds_S) : ;; \ > *) echo "Don't know how to preprocess $(1)"; false ;; \ > esac | sed -rn 's/^.*=== __KSYM_(.*) ===.*$$/KSYM_\1/p'
This makes perfect sense even if I can't reproduce on my side. Are you willing to fold this patch in, or do you prefer that I repost? Nicolas
