On Mon, 29 Jun 2020 at 10:42, Gautham R Shenoy <e...@linux.vnet.ibm.com> wrote: > > On Thu, Jun 25, 2020 at 07:33:49PM +0930, Joel Stanley wrote: > > It's not done anything for a long time. Save the percpu variable, and > > emit a warning to remind users to not expect it to do anything. > > > > Signed-off-by: Joel Stanley <j...@jms.id.au> > > The only known user of "smt_snooze_delay" is the "ppc64_cpu" which > uses the presence of this file to assume that the system is SMT > capable. > > Since we have "/sys/devices/system/cpu/smt/" these days, perhaps the > userspace utility can use that and we can get rid of the file > altogether ?
I've sent a change to the userspace tool to stop using the file. It now uses the device tree parsing that was already present to determine the smt state. https://github.com/ibm-power-utilities/powerpc-utils/pull/43 We will want to wait for the userspace tool to propagate through a release and to distros before we remove the file all together. I agree it should be removed in the future. I've got of this patch v2 that changes the message to be: pr_warn_ratelimited("%s (%d) used unsupported smt_snooze_delay, this has no effect\n", current->comm, current->pid); I'll send that out today. Cheers, Joel > > FWIW, > Acked-by: Gautham R. Shenoy <e...@linux.vnet.ibm.com> > > --- > > arch/powerpc/kernel/sysfs.c | 41 +++++++++++++------------------------ > > 1 file changed, 14 insertions(+), 27 deletions(-) > > > > diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c > > index 571b3259697e..530ae92bc46d 100644 > > --- a/arch/powerpc/kernel/sysfs.c > > +++ b/arch/powerpc/kernel/sysfs.c > > @@ -32,29 +32,25 @@ > > > > static DEFINE_PER_CPU(struct cpu, cpu_devices); > > > > -/* > > - * SMT snooze delay stuff, 64-bit only for now > > - */ > > - > > #ifdef CONFIG_PPC64 > > > > -/* Time in microseconds we delay before sleeping in the idle loop */ > > -static DEFINE_PER_CPU(long, smt_snooze_delay) = { 100 }; > > +/* > > + * Snooze delay has not been hooked up since 3fa8cad82b94 > > ("powerpc/pseries/cpuidle: > > + * smt-snooze-delay cleanup.") and has been broken even longer. As was > > foretold in > > + * 2014: > > + * > > + * "ppc64_util currently utilises it. Once we fix ppc64_util, propose to > > clean > > + * up the kernel code." > > + * > > + * At some point in the future this code should be removed. > > + */ > > > > static ssize_t store_smt_snooze_delay(struct device *dev, > > struct device_attribute *attr, > > const char *buf, > > size_t count) > > { > > - struct cpu *cpu = container_of(dev, struct cpu, dev); > > - ssize_t ret; > > - long snooze; > > - > > - ret = sscanf(buf, "%ld", &snooze); > > - if (ret != 1) > > - return -EINVAL; > > - > > - per_cpu(smt_snooze_delay, cpu->dev.id) = snooze; > > + WARN_ON_ONCE("smt_snooze_delay sysfs file has no effect\n"); > > return count; > > } > > > > @@ -62,9 +58,9 @@ static ssize_t show_smt_snooze_delay(struct device *dev, > > struct device_attribute *attr, > > char *buf) > > { > > - struct cpu *cpu = container_of(dev, struct cpu, dev); > > + WARN_ON_ONCE("smt_snooze_delay sysfs file has no effect\n"); > > > > - return sprintf(buf, "%ld\n", per_cpu(smt_snooze_delay, cpu->dev.id)); > > + return sprintf(buf, "100\n"); > > } > > > > static DEVICE_ATTR(smt_snooze_delay, 0644, show_smt_snooze_delay, > > @@ -72,16 +68,7 @@ static DEVICE_ATTR(smt_snooze_delay, 0644, > > show_smt_snooze_delay, > > > > static int __init setup_smt_snooze_delay(char *str) > > { > > - unsigned int cpu; > > - long snooze; > > - > > - if (!cpu_has_feature(CPU_FTR_SMT)) > > - return 1; > > - > > - snooze = simple_strtol(str, NULL, 10); > > - for_each_possible_cpu(cpu) > > - per_cpu(smt_snooze_delay, cpu) = snooze; > > - > > + WARN_ON_ONCE("smt-snooze-delay command line option has no effect\n"); > > return 1; > > } > > __setup("smt-snooze-delay=", setup_smt_snooze_delay); > > -- > > 2.27.0 > >
