I think this is the case also for entry_flush. compiling with W=1 will tell you more.
When I use these commands:
make allmodconfig ARCH=powerpc CROSS_COMPILE=powerpc64-linux-gnu-
make C=2 arch/powerpc/kernel/setup_64.o ARCH=powerpc CROSS_COMPILE=powerpc64-linux-gnu-
I find warnings as followings:
arch/powerpc/kernel/setup_64.c:422:6: warning: symbol 'panic_smp_self_stop' was not declared. Should it be static?
arch/powerpc/kernel/setup_64.c:951:6: warning: symbol 'rfi_flush' was not declared. Should it be static?
arch/powerpc/kernel/setup_64.c:952:6: warning: symbol 'entry_flush' was not declared. Should it be static?
arch/powerpc/kernel/setup_64.c:953:6: warning: symbol 'uaccess_flush' was not declared. Should it be static?
When I use the command "make W=1 arch/powerpc/kernel/setup_64.o ARCH=powerpc CROSS_COMPILE=powerpc64-linux-gnu-", warning becomes this:
arch/powerpc/kernel/setup_64.c:422:6: warning: no previous prototype for ‘panic_smp_self_stop’ [-Wmissing-prototypes]
void panic_smp_self_stop(void)
^~~~~~~~~~~~~~~~~~~
My sparse tool is the latest one with the version "v0.6.3". So, should I fix all the warnings reported by sparse?