Re: [PATCH] kbuild: don't delete in-flight filechk temporaries in asm-headers

[Nicolas Schier]

On Wed, Sep 02, 2026 at 11:45:44PM -0700, Nathan Chancellor wrote:
> On Wed, Sep 02, 2026 at 09:13:47AM -0700, Vlad Poenaru wrote:
> > Commit 2d69b891e646 ("kbuild: Support generated asm-headers in
> > subdirectories") switched the stale-wrapper sweep in
> > scripts/Makefile.asm-headers from $(wildcard $(obj)/*.h) to a find(1)
> > invocation, so that generated headers in subdirectories are considered.
> > 
> > The two do not match the same set of files. Make's $(wildcard) uses glob
> > semantics, where a leading '.' has to be matched explicitly, whereas
> > find's -name uses fnmatch() without FNM_PERIOD, so '*.h' matches
> > dotfiles as well. filechk writes its output to $(dir $@).tmp_$(notdir $@)
> > before renaming it into place, so such a scratch file, if it happens to
> > exist in $(obj) when the sub-make is parsed, is now picked up in
> > old-headers. It appears in neither generic-y, generated-y nor syscall-y,
> > is therefore classified as unwanted, and cmd_remove deletes it.
> > 
> > On x86 this races with archprepare, which lists both asm-generic and
> > arch/x86/include/generated/asm/cpufeaturemasks.h as prerequisites. Under
> > -j they run concurrently against the same directory, and the build fails
> > intermittently:
> > 
> >   mv: cannot stat 'arch/x86/include/generated/asm/.tmp_cpufeaturemasks.h': No such file or directory
> >   make[1]: *** [arch/x86/Makefile:269: arch/x86/include/generated/asm/cpufeaturemasks.h] Error 1
> > 
> > The same commit also converted the generic wrapper rule to filechk, so
> > those wrappers now create .tmp_*.h in $(obj) too and can race among
> > themselves.
> > 
> > Restore the previous behaviour by excluding dotfiles from the sweep.
> > Subdirectories, which is what the find(1) conversion was for, keep being
> > descended into. While at it, quote the -name argument: it is currently
> > expanded by the shell against the build directory before find sees it.
> > 
> > Fixes: 2d69b891e646 ("kbuild: Support generated asm-headers in subdirectories")
> > Signed-off-by: Vlad Poenaru <vlad.wing@xxxxxxxxx>
> 
> Oof :( that's unfortunate, thanks a lot for tracking this down!
> 
> Reviewed-by: Nathan Chancellor <nathan@xxxxxxxxxx>
> 
> Nicolas, I assume you will pick this up for 7.3.

Sure, sorry for the delay.

Reviewed-by: Nicolas Schier <n.schier@xxxxxxxxx>

-- 
Nicolas