On Fri, Sep 06, 2013 at 08:50:41PM +0200, Geert Uytterhoeven wrote: > On Fri, Sep 6, 2013 at 7:30 PM, Paul E. McKenney > <paulmck@xxxxxxxxxxxxxxxxxx> wrote: > >> Furthermore, it seems only hexagon, metag, mips, and x86 set NR_CPUS to 1 > >> if !SMP. On other architectures, NR_CPUS is not defined and presumed to be 0. > > > > Would it make sense to require that NR_CPUS=1 for !SMP? > > Yes, this looks reasonable to me. > > > I tried creating a NR_CPUS_REALLY as follows: > > > > config NR_CPUS_REALLY > > int "Fixed version of NR_CPUS" > > default NR_CPUS if NR_CPUS > > default 1 if !NR_CPUS > > > > But this still gave a warning on the first "default" even though it > > was not in effect. I also tried using Kconfig "if": > > IIRC, it tries to use the first default first, so the below may work > (the "if SMP" is probably not needed): > > config NR_CPUS_REALLY > int "Fixed version of NR_CPUS" > default 1 if !SMP > default NR_CPUS if SMP Seemed like a good idea, but I still get: make O=/tmp/e ARCH=m68k defconfig GEN /tmp/e/Makefile *** Default configuration is based on 'multi_defconfig' kernel/time/Kconfig:140:warning: 'NR_CPUS_REALLY': number is invalid # # configuration written to .config # Diff below in case I messed something up. > > Defining NR_CPUS=1 if !SMP is looking pretty good to me just now. > > This would probably have other benefits -- I cannot be the only > > person who ever wanted this. ;-) > > Sure. I just didn't want to create patches for all architectures without > having a discussion first. > > And it would be nice if it cuould be done in a central place, without > touching all architectures. Agreed, should it prove possible. ;-) Thanx, Paul ------------------------------------------------------------------------ diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig index 3381f09..cb7a932 100644 --- a/kernel/time/Kconfig +++ b/kernel/time/Kconfig @@ -134,6 +134,11 @@ config NO_HZ_FULL_ALL Note the boot CPU will still be kept outside the range to handle the timekeeping duty. +config NR_CPUS_REALLY + int "Fixed version of NR_CPUS" + default 1 if !SMP + default NR_CPUS if SMP + config NO_HZ_FULL_SYSIDLE bool "Detect full-system idle state for full dynticks system" depends on NO_HZ_FULL @@ -160,7 +165,7 @@ config NO_HZ_FULL_SYSIDLE config NO_HZ_FULL_SYSIDLE_SMALL int "Number of CPUs above which large-system approach is used" depends on NO_HZ_FULL_SYSIDLE - range 1 NR_CPUS + range 1 NR_CPUS_REALLY default 8 help The full-system idle detection mechanism takes a lazy approach -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
