[PATCH 02/12] x86: Replace cpu_up/down with devcie_online/offline

Qais Yousef
2019-10-30T15:42:13Z

The core device API performs extra housekeeping bits that are missing
from directly calling cpu_up/down.

See commit a6717c01ddc2 ("powerpc/rtas: use device model APIs and
serialization during LPM") for an example description of what might go
wrong.

This also prepares to make cpu_up/down a private interface for anything
but the cpu subsystem.

Signed-off-by: Qais Yousef <qais.yousef@arm.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Ingo Molnar <mingo@redhat.com>
CC: Borislav Petkov <bp@alien8.de>
CC: "H. Peter Anvin" <hpa@zytor.com>
CC: x86@kernel.org
CC: linux-kernel@vger.kernel.org
---
arch/x86/kernel/topology.c | 4 ++--
arch/x86/mm/mmio-mod.c | 8 ++++++--
arch/x86/xen/smp.c | 4 +++-
3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/topology.c b/arch/x86/kernel/topology.c
index be5bc2e47c71..3b253088615e 100644
--- a/arch/x86/kernel/topology.c
+++ b/arch/x86/kernel/topology.c
@@ -69,7 +69,7 @@ int _debug_hotplug_cpu(int cpu, int action)

switch (action) {
case 0:
- ret = cpu_down(cpu);
+ ret = device_offline(get_cpu_device(cpu));
if (!ret) {
pr_info("DEBUG_HOTPLUG_CPU0: CPU %u is now offline\n", cpu);
dev->offline = true;
@@ -78,7 +78,7 @@ int _debug_hotplug_cpu(int cpu, int action)
pr_debug("Can't offline CPU%d.\n", cpu);
break;
case 1:
- ret = cpu_up(cpu);
+ ret = device_online(get_cpu_device(cpu));
if (!ret) {
dev->offline = false;
kobject_uevent(&dev->kobj, KOBJ_ONLINE);
diff --git a/arch/x86/mm/mmio-mod.c b/arch/x86/mm/mmio-mod.c
index b8ef8557d4b3..7ec7d05335ce 100644
--- a/arch/x86/mm/mmio-mod.c
+++ b/arch/x86/mm/mmio-mod.c
@@ -385,13 +385,15 @@ static void enter_uniprocessor(void)
pr_notice("Disabling non-boot CPUs...\n");
put_online_cpus();

+ lock_device_hotplug();
for_each_cpu(cpu, downed_cpus) {
- err = cpu_down(cpu);
+ err = device_offline(get_cpu_device(cpu));
if (!err)
pr_info("CPU%d is down.\n", cpu);
else
pr_err("Error taking CPU%d down: %d\n", cpu, err);
}
+ unlock_device_hotplug();
out:
if (num_online_cpus() > 1)
pr_warning("multiple CPUs still online, may miss events.\n");
@@ -405,13 +407,15 @@ static void leave_uniprocessor(void)
if (downed_cpus == NULL || cpumask_weight(downed_cpus) == 0)
return;
pr_notice("Re-enabling CPUs...\n");
+ lock_device_hotplug();
for_each_cpu(cpu, downed_cpus) {
- err = cpu_up(cpu);
+ err = device_online(get_cpu_device(cpu));
if (!err)
pr_info("enabled CPU%d.\n", cpu);
else
pr_err("cannot re-enable CPU%d: %d\n", cpu, err);
}
+ unlock_device_hotplug();
}

#else /* !CONFIG_HOTPLUG_CPU */
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index 7a43b2ae19f1..aaa31100a31e 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -128,11 +128,12 @@ void __init xen_smp_cpus_done(unsigned int max_cpus)
if (xen_have_vcpu_info_placement)
return;

+ lock_device_hotplug();
for_each_online_cpu(cpu) {
if (xen_vcpu_nr(cpu) < MAX_VIRT_CPUS)
continue;

- rc = cpu_down(cpu);
+ rc = device_offline(get_cpu_device(cpu));

if (rc == 0) {
/*
@@ -145,6 +146,7 @@ void __init xen_smp_cpus_done(unsigned int max_cpus)
__func__, cpu, rc);
}
}
+ unlock_device_hotplug();
WARN(count, "%s: brought %d CPUs offline\n", __func__, count);
}

--
2.17.1