On 6/25/20 3:29 AM, Christophe Leroy wrote: > > > Le 25/06/2020 à 12:03, Joel Stanley a écrit : >> 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. > > Why not just drop the file entirely if it is useless ?
Userspace tooling that hasn't learned its useless yet. Joel has also submitted a pull request for the ppc64_util tool in question to drop using this interface. -Tyrel > > Christophe > >> >> Signed-off-by: Joel Stanley <j...@jms.id.au> >> --- >> 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); >>