4.18-stable review patch. If anyone has any objections, please let me know.
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From: Thomas Gleixner tglx@linutronix.de
Writing 'off' to /sys/devices/system/cpu/smt/control offlines all SMT siblings. Writing 'on' merily enables the abilify to online them, but does not online them automatically.
Make 'on' more useful by onlining all offline siblings.
Signed-off-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/cpu.c | 26 ++++++++++++++++++++++++-- 1 file changed, 24 insertions(+), 2 deletions(-)
--- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -1979,6 +1979,15 @@ static void cpuhp_offline_cpu_device(uns kobject_uevent(&dev->kobj, KOBJ_OFFLINE); }
+static void cpuhp_online_cpu_device(unsigned int cpu) +{ + struct device *dev = get_cpu_device(cpu); + + dev->offline = false; + /* Tell user space about the state change */ + kobject_uevent(&dev->kobj, KOBJ_ONLINE); +} + static int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval) { int cpu, ret = 0; @@ -2011,11 +2020,24 @@ static int cpuhp_smt_disable(enum cpuhp_ return ret; }
-static void cpuhp_smt_enable(void) +static int cpuhp_smt_enable(void) { + int cpu, ret = 0; + cpu_maps_update_begin(); cpu_smt_control = CPU_SMT_ENABLED; + for_each_present_cpu(cpu) { + /* Skip online CPUs and CPUs on offline nodes */ + if (cpu_online(cpu) || !node_online(cpu_to_node(cpu))) + continue; + ret = _cpu_up(cpu, 0, CPUHP_ONLINE); + if (ret) + break; + /* See comment in cpuhp_smt_disable() */ + cpuhp_online_cpu_device(cpu); + } cpu_maps_update_done(); + return ret; }
static ssize_t @@ -2046,7 +2068,7 @@ store_smt_control(struct device *dev, st if (ctrlval != cpu_smt_control) { switch (ctrlval) { case CPU_SMT_ENABLED: - cpuhp_smt_enable(); + ret = cpuhp_smt_enable(); break; case CPU_SMT_DISABLED: case CPU_SMT_FORCE_DISABLED: