On Mon, Sep 10, 2018 at 10:59:56AM -0700, Paulo Zanoni wrote: > As a Kernel developer, I make heavy use of "make targz-pkg" in order > to locally compile and remotely install my development Kernels. The > nice feature I rely on is that after a normal "make", "make targz-pkg" > only generates the tarball without having to recompile everything. > > That was true until commit f28bc3c32c05 ("tracing: Handle > CC_FLAGS_FTRACE more accurately"). After it, running "make targz-pkg" > after "make" will recompile the whole Kernel tree, making my > development workflow much slower. > > The Kernel is choosing to recompile everything because it claims the > command line has changed. A diff of the .cmd files show a repeated > -mfentry in one of the files. That is because "make targz-pkg" calls > "make modules_install" and the environment is already populated with > the exported variables, CC_FLAGS_FTRACE being one of them. Then, > -mfentry gets duplicated because it is not protected behind an ifndef > block, like -pg. > > To complicate the problem a little bit more, architectures can define > their own version CC_FLAGS_FTRACE, so our code not only has to > consider recursive Makefiles, but also architecture overrides. > > So in this patch we move CC_FLAGFS_FTRACE up and unconditionally CC_FLAGS_FTRACE > define it to -pg. Then we let the architecture Makefiles possibly > override it, and finally append the extra options later. This ensures > the variable is always fully redefined at each invocation so recursive > Makefiles don't keep appending, and hopefully it maintains the > intended behavior on how architectures can override the defaults.. > > Thanks Steven Rostedt and Vasily Gorbik for the help on this > regression. > > Fixes: commit f28bc3c32c05 ("tracing: Handle CC_FLAGS_FTRACE more > accurately") > Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx> > Cc: Michal Marek <michal.lkml@xxxxxxxxxxx> > Cc: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> > Cc: Ingo Molnar <mingo@xxxxxxxxxx> > Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx> > Cc: linux-kbuild@xxxxxxxxxxxxxxx > Signed-off-by: Paulo Zanoni <paulo.r.zanoni@xxxxxxxxx> > --- > Makefile | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/Makefile b/Makefile > index 4d5c883a98e5..a5ef6818157a 100644 > --- a/Makefile > +++ b/Makefile > @@ -616,6 +616,11 @@ CFLAGS_GCOV := -fprofile-arcs -ftest-coverage \ > $(call cc-disable-warning,maybe-uninitialized,) > export CFLAGS_GCOV > > +# The arch Makefiles can override CC_FLAGS_FTRACE. We may also append it later. > +ifdef CONFIG_FUNCTION_TRACER > + CC_FLAGS_FTRACE := -pg > +endif > + > # The arch Makefile can set ARCH_{CPP,A,C}FLAGS to override the default > # values of the respective KBUILD_* variables > ARCH_CPPFLAGS := > @@ -755,9 +760,6 @@ KBUILD_CFLAGS += $(call cc-option, -femit-struct-debug-baseonly) \ > endif > > ifdef CONFIG_FUNCTION_TRACER > -ifndef CC_FLAGS_FTRACE > -CC_FLAGS_FTRACE := -pg > -endif > ifdef CONFIG_FTRACE_MCOUNT_RECORD > # gcc 5 supports generating the mcount tables directly > ifeq ($(call cc-option-yn,-mrecord-mcount),y) > -- > 2.17.1 > Acked-by: Vasily Gorbik <gor@xxxxxxxxxxxxx>