Export cpu_hotplug_enable/cpu_hotplug_disable functions from cpu.c and use
them instead of altering the smp_ops.cpu_disable in Hyper-V vmbus module.
Vitaly Kuznetsov (2):
cpu-hotplug: export cpu_hotplug_enable/cpu_hotplug_disable
Drivers: hv: vmbus: use cpu_hotplug_enable/disable
drivers/hv/vmbus_drv.c | 38 ++++----------------------------------
kernel/cpu.c | 3 ++-
2 files changed, 6 insertions(+), 35 deletions(-)
--
1.9.3
Loaded Hyper-V module will use these functions to disable CPU hotplug
under certain circumstances.
Signed-off-by: Vitaly Kuznetsov <[email protected]>
---
kernel/cpu.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 94bbe46..dc005e7 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -193,6 +193,7 @@ void cpu_hotplug_disable(void)
cpu_hotplug_disabled = 1;
cpu_maps_update_done();
}
+EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
void cpu_hotplug_enable(void)
{
@@ -200,7 +201,7 @@ void cpu_hotplug_enable(void)
cpu_hotplug_disabled = 0;
cpu_maps_update_done();
}
-
+EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
#endif /* CONFIG_HOTPLUG_CPU */
/* Need to know about CPUs going up/down? */
--
1.9.3
Commit e513229b4c38 ("Drivers: hv: vmbus: prevent cpu offlining on newer
hypervisors") was alteringd smp_ops.cpu_disable to prevent CPU offlining.
We can bo better by using cpu_hotplug_enable/disable functions instead of
such hard-coding.
Reported-by: Radim Krčmář <[email protected]>
Signed-off-by: Vitaly Kuznetsov <[email protected]>
---
drivers/hv/vmbus_drv.c | 38 ++++----------------------------------
1 file changed, 4 insertions(+), 34 deletions(-)
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index c85235e..e916ba2 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -763,38 +763,6 @@ static void vmbus_isr(void)
}
}
-#ifdef CONFIG_HOTPLUG_CPU
-static int hyperv_cpu_disable(void)
-{
- return -ENOSYS;
-}
-
-static void hv_cpu_hotplug_quirk(bool vmbus_loaded)
-{
- static void *previous_cpu_disable;
-
- /*
- * Offlining a CPU when running on newer hypervisors (WS2012R2, Win8,
- * ...) is not supported at this moment as channel interrupts are
- * distributed across all of them.
- */
-
- if ((vmbus_proto_version == VERSION_WS2008) ||
- (vmbus_proto_version == VERSION_WIN7))
- return;
-
- if (vmbus_loaded) {
- previous_cpu_disable = smp_ops.cpu_disable;
- smp_ops.cpu_disable = hyperv_cpu_disable;
- pr_notice("CPU offlining is not supported by hypervisor\n");
- } else if (previous_cpu_disable)
- smp_ops.cpu_disable = previous_cpu_disable;
-}
-#else
-static void hv_cpu_hotplug_quirk(bool vmbus_loaded)
-{
-}
-#endif
/*
* vmbus_bus_init -Main vmbus driver initialization routine.
@@ -836,7 +804,8 @@ static int vmbus_bus_init(int irq)
if (ret)
goto err_alloc;
- hv_cpu_hotplug_quirk(true);
+ if (vmbus_proto_version > VERSION_WIN7)
+ cpu_hotplug_disable();
/*
* Only register if the crash MSRs are available
@@ -1103,7 +1072,8 @@ static void __exit vmbus_exit(void)
for_each_online_cpu(cpu)
smp_call_function_single(cpu, hv_synic_cleanup, NULL, 1);
acpi_bus_unregister_driver(&vmbus_acpi_driver);
- hv_cpu_hotplug_quirk(false);
+ if (vmbus_proto_version > VERSION_WIN7)
+ cpu_hotplug_enable();
vmbus_disconnect();
}
--
1.9.3
2015-05-19 14:15+0200, Vitaly Kuznetsov:
> Loaded Hyper-V module will use these functions to disable CPU hotplug
> under certain circumstances.
>
> Signed-off-by: Vitaly Kuznetsov <[email protected]>
> ---
> kernel/cpu.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/cpu.c b/kernel/cpu.c
> index 94bbe46..dc005e7 100644
> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -193,6 +193,7 @@ void cpu_hotplug_disable(void)
> cpu_hotplug_disabled = 1;
(I think it would be safer to make this into a counter, at least, so
cpu_hotplug_disable() |
| cpu_hotplug_disable()
cpu_hotplug_enable() |
wouldn't end up with enabled hotplug, when this switch is intended for
hotplug-and-die situations.)
> cpu_maps_update_done();
> }
> +EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
>
> void cpu_hotplug_enable(void)
> {
> @@ -200,7 +201,7 @@ void cpu_hotplug_enable(void)
> cpu_hotplug_disabled = 0;
> cpu_maps_update_done();
> }
> -
> +EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
> #endif /* CONFIG_HOTPLUG_CPU */
>
> /* Need to know about CPUs going up/down? */
> --
> 1.9.3
>
On Tue, May 19, 2015 at 02:15:41PM +0200, Vitaly Kuznetsov wrote:
> Loaded Hyper-V module will use these functions to disable CPU hotplug
> under certain circumstances.
What's wrong with get_online_cpus() ?
Peter Zijlstra <[email protected]> writes:
> On Tue, May 19, 2015 at 02:15:41PM +0200, Vitaly Kuznetsov wrote:
>> Loaded Hyper-V module will use these functions to disable CPU hotplug
>> under certain circumstances.
>
> What's wrong with get_online_cpus() ?
We need to disable cpu offlining permanently (till the module is
unloaded but this is highly unlikely). If we do get_online_cpus()
instead we get
# echo 0 > /sys/devices/system/cpu/cpu1/online
<nothing happens, pemanent hang followed by the following:>
[ 240.247109] INFO: task bash:972 blocked for more than 120 seconds.
[ 240.248937] Not tainted 4.1.0-rc3_bug1167380_test_rkr+ #602
[ 240.250515] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
disables this message.
[ 240.252379] bash D ffff880021b83c18 0 972 939
0x00000004
[ 240.255068] ffff880021b83c18 0000000000000001 0000000000000046
ffff880021b83be8
[ 240.258140] ffffffff81fdcdb0 ffff880037dbcfc0 ffff880037203bd0
ffffffff81fdcdb8
[ 240.261275] ffff880021b84000 0000000000000001 0000000000000000
0000000000000001
[ 240.264402] Call Trace:
[ 240.265423] [<ffffffff81aecf77>] schedule+0x37/0x90
[ 240.266748] [<ffffffff81081872>] cpu_hotplug_begin+0xd2/0xe0
[ 240.268210] [<ffffffff810817a5>] ? cpu_hotplug_begin+0x5/0xe0
[ 240.269675] [<ffffffff810cb860>] ? prepare_to_wait_event+0xf0/0xf0
[ 240.271285] [<ffffffff81ad561a>] _cpu_down+0x8a/0x300
[ 240.275294] [<ffffffff81ad58c6>] cpu_down+0x36/0x50
[ 240.276680] [<ffffffff8160f954>] cpu_subsys_offline+0x14/0x20
[ 240.278145] [<ffffffff8160a505>] device_offline+0xa5/0xd0
[ 240.279618] [<ffffffff8160a620>] online_store+0x50/0xa0
[ 240.280991] [<ffffffff81607678>] dev_attr_store+0x18/0x30
...
And if we do the cpu_hotplug_disable() call we get:
# echo 0 > /sys/devices/system/cpu/cpu1/online
-bash: echo: write error: Device or resource busy
This behavior is preferable.
--
Vitaly
> -----Original Message-----
> From: Vitaly Kuznetsov [mailto:[email protected]]
> Sent: Tuesday, May 19, 2015 5:16 AM
> To: [email protected]
> Cc: KY Srinivasan; Haiyang Zhang; [email protected]; Dexuan Cui;
> Ingo Molnar; Paul E. McKenney; Rafael J. Wysocki; Peter Zijlstra; Thomas
> Gleixner; Radim Krčmář
> Subject: [PATCH 0/2] Drivers: hv: vmbus: use cpu_hotplug_enable/disable
> for CPU offlining prevention
>
> Export cpu_hotplug_enable/cpu_hotplug_disable functions from cpu.c and
> use
> them instead of altering the smp_ops.cpu_disable in Hyper-V vmbus
> module.
>
> Vitaly Kuznetsov (2):
> cpu-hotplug: export cpu_hotplug_enable/cpu_hotplug_disable
> Drivers: hv: vmbus: use cpu_hotplug_enable/disable
>
> drivers/hv/vmbus_drv.c | 38 ++++----------------------------------
> kernel/cpu.c | 3 ++-
> 2 files changed, 6 insertions(+), 35 deletions(-)
Greg,
Can you take both these patches through your tree.
Regards,
K. Y
>
> --
> 1.9.3
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