| Message ID | 1594896024-16624-1-git-send-email-chenhc@lemote.com (mailing list archive) |
|---|---|
| State | Mainlined |
| Commit | 9cce844abf07b683cff5f0273977d5f8d0af94c7 |
| Headers | show |
| Series | [V2] MIPS: CPU#0 is not hotpluggable | expand |
Hi, Thomas,
What do you think about this patch? Other archs also do the same thing
except those support hotplug CPU#0.
grep hotpluggable arch -rwI
arch/riscv/kernel/setup.c: cpu->hotpluggable = cpu_has_hotplug(i);
arch/powerpc/kernel/sysfs.c: BUG_ON(!c->hotpluggable);
arch/powerpc/kernel/sysfs.c: c->hotpluggable = 1;
arch/powerpc/kernel/sysfs.c: if (cpu_online(cpu) || c->hotpluggable) {
arch/arm/kernel/setup.c: cpuinfo->cpu.hotpluggable =
platform_can_hotplug_cpu(cpu);
arch/sh/kernel/topology.c: c->hotpluggable = 1;
arch/ia64/kernel/topology.c: * CPEI target, then it is hotpluggable
arch/ia64/kernel/topology.c: sysfs_cpus[num].cpu.hotpluggable = 1;
arch/xtensa/kernel/setup.c: cpu->hotpluggable = !!i;
arch/s390/kernel/smp.c: c->hotpluggable = 1;
arch/mips/kernel/topology.c: c->hotpluggable = 1;
arch/arm64/kernel/cpuinfo.c: * In case the boot CPU is hotpluggable,
we record its initial state and
arch/arm64/kernel/setup.c: cpu->hotpluggable = cpu_can_disable(i);
arch/x86/kernel/topology.c: per_cpu(cpu_devices,
num).cpu.hotpluggable = 1;
On Thu, Jul 16, 2020 at 6:38 PM Huacai Chen <chenhc@lemote.com> wrote:
>
> Now CPU#0 is not hotpluggable on MIPS, so prevent to create /sys/devices
> /system/cpu/cpu0/online which confuses some user-space tools.
>
> Cc: stable@vger.kernel.org
> Signed-off-by: Huacai Chen <chenhc@lemote.com>
> ---
> arch/mips/kernel/topology.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/mips/kernel/topology.c b/arch/mips/kernel/topology.c
> index cd3e1f8..08ad637 100644
> --- a/arch/mips/kernel/topology.c
> +++ b/arch/mips/kernel/topology.c
> @@ -20,7 +20,7 @@ static int __init topology_init(void)
> for_each_present_cpu(i) {
> struct cpu *c = &per_cpu(cpu_devices, i);
>
> - c->hotpluggable = 1;
> + c->hotpluggable = !!i;
> ret = register_cpu(c, i);
> if (ret)
> printk(KERN_WARNING "topology_init: register_cpu %d "
> --
> 2.7.0
>
On Sat, Jul 25, 2020 at 02:37:52PM +0800, Huacai Chen wrote: > Hi, Thomas, > > What do you think about this patch? Other archs also do the same thing > except those support hotplug CPU#0. > > grep hotpluggable arch -rwI > arch/riscv/kernel/setup.c: cpu->hotpluggable = cpu_has_hotplug(i); > arch/powerpc/kernel/sysfs.c: BUG_ON(!c->hotpluggable); > arch/powerpc/kernel/sysfs.c: c->hotpluggable = 1; > arch/powerpc/kernel/sysfs.c: if (cpu_online(cpu) || c->hotpluggable) { > arch/arm/kernel/setup.c: cpuinfo->cpu.hotpluggable = > platform_can_hotplug_cpu(cpu); > arch/sh/kernel/topology.c: c->hotpluggable = 1; > arch/ia64/kernel/topology.c: * CPEI target, then it is hotpluggable > arch/ia64/kernel/topology.c: sysfs_cpus[num].cpu.hotpluggable = 1; > arch/xtensa/kernel/setup.c: cpu->hotpluggable = !!i; > arch/s390/kernel/smp.c: c->hotpluggable = 1; > arch/mips/kernel/topology.c: c->hotpluggable = 1; > arch/arm64/kernel/cpuinfo.c: * In case the boot CPU is hotpluggable, > we record its initial state and > arch/arm64/kernel/setup.c: cpu->hotpluggable = cpu_can_disable(i); > arch/x86/kernel/topology.c: per_cpu(cpu_devices, > num).cpu.hotpluggable = 1; > > On Thu, Jul 16, 2020 at 6:38 PM Huacai Chen <chenhc@lemote.com> wrote: > > > > Now CPU#0 is not hotpluggable on MIPS, so prevent to create /sys/devices > > /system/cpu/cpu0/online which confuses some user-space tools. What userspace tools are confused by this? They should be able to handle a cpu not being able to be removed, right? > > > > Cc: stable@vger.kernel.org > > Signed-off-by: Huacai Chen <chenhc@lemote.com> > > --- > > arch/mips/kernel/topology.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/arch/mips/kernel/topology.c b/arch/mips/kernel/topology.c > > index cd3e1f8..08ad637 100644 > > --- a/arch/mips/kernel/topology.c > > +++ b/arch/mips/kernel/topology.c > > @@ -20,7 +20,7 @@ static int __init topology_init(void) > > for_each_present_cpu(i) { > > struct cpu *c = &per_cpu(cpu_devices, i); > > > > - c->hotpluggable = 1; > > + c->hotpluggable = !!i; Seems to be the same as what xtensa did, so it's probably not a big deal. thanks, greg k-h
Hi Greg, On Sat, Jul 25, 2020 at 2:49 PM Greg KH <gregkh@linuxfoundation.org> wrote: > > On Sat, Jul 25, 2020 at 02:37:52PM +0800, Huacai Chen wrote: > > Hi, Thomas, > > > > What do you think about this patch? Other archs also do the same thing > > except those support hotplug CPU#0. > > > > grep hotpluggable arch -rwI > > arch/riscv/kernel/setup.c: cpu->hotpluggable = cpu_has_hotplug(i); > > arch/powerpc/kernel/sysfs.c: BUG_ON(!c->hotpluggable); > > arch/powerpc/kernel/sysfs.c: c->hotpluggable = 1; > > arch/powerpc/kernel/sysfs.c: if (cpu_online(cpu) || c->hotpluggable) { > > arch/arm/kernel/setup.c: cpuinfo->cpu.hotpluggable = > > platform_can_hotplug_cpu(cpu); > > arch/sh/kernel/topology.c: c->hotpluggable = 1; > > arch/ia64/kernel/topology.c: * CPEI target, then it is hotpluggable > > arch/ia64/kernel/topology.c: sysfs_cpus[num].cpu.hotpluggable = 1; > > arch/xtensa/kernel/setup.c: cpu->hotpluggable = !!i; > > arch/s390/kernel/smp.c: c->hotpluggable = 1; > > arch/mips/kernel/topology.c: c->hotpluggable = 1; > > arch/arm64/kernel/cpuinfo.c: * In case the boot CPU is hotpluggable, > > we record its initial state and > > arch/arm64/kernel/setup.c: cpu->hotpluggable = cpu_can_disable(i); > > arch/x86/kernel/topology.c: per_cpu(cpu_devices, > > num).cpu.hotpluggable = 1; > > > > On Thu, Jul 16, 2020 at 6:38 PM Huacai Chen <chenhc@lemote.com> wrote: > > > > > > Now CPU#0 is not hotpluggable on MIPS, so prevent to create /sys/devices > > > /system/cpu/cpu0/online which confuses some user-space tools. > > What userspace tools are confused by this? They should be able to > handle a cpu not being able to be removed, right? It causes ltp's "hotplug" test fails, and ltp considers CPUs with a "online" node be hotpluggable. > > > > > > > > Cc: stable@vger.kernel.org > > > Signed-off-by: Huacai Chen <chenhc@lemote.com> > > > --- > > > arch/mips/kernel/topology.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/arch/mips/kernel/topology.c b/arch/mips/kernel/topology.c > > > index cd3e1f8..08ad637 100644 > > > --- a/arch/mips/kernel/topology.c > > > +++ b/arch/mips/kernel/topology.c > > > @@ -20,7 +20,7 @@ static int __init topology_init(void) > > > for_each_present_cpu(i) { > > > struct cpu *c = &per_cpu(cpu_devices, i); > > > > > > - c->hotpluggable = 1; > > > + c->hotpluggable = !!i; > > Seems to be the same as what xtensa did, so it's probably not a big > deal. > > thanks, > > greg k-h
On Sat, Jul 25, 2020 at 02:57:31PM +0800, Huacai Chen wrote: > Hi Greg, > > On Sat, Jul 25, 2020 at 2:49 PM Greg KH <gregkh@linuxfoundation.org> wrote: > > > > On Sat, Jul 25, 2020 at 02:37:52PM +0800, Huacai Chen wrote: > > > Hi, Thomas, > > > > > > What do you think about this patch? Other archs also do the same thing > > > except those support hotplug CPU#0. > > > > > > grep hotpluggable arch -rwI > > > arch/riscv/kernel/setup.c: cpu->hotpluggable = cpu_has_hotplug(i); > > > arch/powerpc/kernel/sysfs.c: BUG_ON(!c->hotpluggable); > > > arch/powerpc/kernel/sysfs.c: c->hotpluggable = 1; > > > arch/powerpc/kernel/sysfs.c: if (cpu_online(cpu) || c->hotpluggable) { > > > arch/arm/kernel/setup.c: cpuinfo->cpu.hotpluggable = > > > platform_can_hotplug_cpu(cpu); > > > arch/sh/kernel/topology.c: c->hotpluggable = 1; > > > arch/ia64/kernel/topology.c: * CPEI target, then it is hotpluggable > > > arch/ia64/kernel/topology.c: sysfs_cpus[num].cpu.hotpluggable = 1; > > > arch/xtensa/kernel/setup.c: cpu->hotpluggable = !!i; > > > arch/s390/kernel/smp.c: c->hotpluggable = 1; > > > arch/mips/kernel/topology.c: c->hotpluggable = 1; > > > arch/arm64/kernel/cpuinfo.c: * In case the boot CPU is hotpluggable, > > > we record its initial state and > > > arch/arm64/kernel/setup.c: cpu->hotpluggable = cpu_can_disable(i); > > > arch/x86/kernel/topology.c: per_cpu(cpu_devices, > > > num).cpu.hotpluggable = 1; > > > > > > On Thu, Jul 16, 2020 at 6:38 PM Huacai Chen <chenhc@lemote.com> wrote: > > > > > > > > Now CPU#0 is not hotpluggable on MIPS, so prevent to create /sys/devices > > > > /system/cpu/cpu0/online which confuses some user-space tools. > > > > What userspace tools are confused by this? They should be able to > > handle a cpu not being able to be removed, right? > It causes ltp's "hotplug" test fails, and ltp considers CPUs with a > "online" node be hotpluggable. Is that always true?
Hi, Greg, On Sat, Jul 25, 2020 at 3:45 PM Greg KH <gregkh@linuxfoundation.org> wrote: > > On Sat, Jul 25, 2020 at 02:57:31PM +0800, Huacai Chen wrote: > > Hi Greg, > > > > On Sat, Jul 25, 2020 at 2:49 PM Greg KH <gregkh@linuxfoundation.org> wrote: > > > > > > On Sat, Jul 25, 2020 at 02:37:52PM +0800, Huacai Chen wrote: > > > > Hi, Thomas, > > > > > > > > What do you think about this patch? Other archs also do the same thing > > > > except those support hotplug CPU#0. > > > > > > > > grep hotpluggable arch -rwI > > > > arch/riscv/kernel/setup.c: cpu->hotpluggable = cpu_has_hotplug(i); > > > > arch/powerpc/kernel/sysfs.c: BUG_ON(!c->hotpluggable); > > > > arch/powerpc/kernel/sysfs.c: c->hotpluggable = 1; > > > > arch/powerpc/kernel/sysfs.c: if (cpu_online(cpu) || c->hotpluggable) { > > > > arch/arm/kernel/setup.c: cpuinfo->cpu.hotpluggable = > > > > platform_can_hotplug_cpu(cpu); > > > > arch/sh/kernel/topology.c: c->hotpluggable = 1; > > > > arch/ia64/kernel/topology.c: * CPEI target, then it is hotpluggable > > > > arch/ia64/kernel/topology.c: sysfs_cpus[num].cpu.hotpluggable = 1; > > > > arch/xtensa/kernel/setup.c: cpu->hotpluggable = !!i; > > > > arch/s390/kernel/smp.c: c->hotpluggable = 1; > > > > arch/mips/kernel/topology.c: c->hotpluggable = 1; > > > > arch/arm64/kernel/cpuinfo.c: * In case the boot CPU is hotpluggable, > > > > we record its initial state and > > > > arch/arm64/kernel/setup.c: cpu->hotpluggable = cpu_can_disable(i); > > > > arch/x86/kernel/topology.c: per_cpu(cpu_devices, > > > > num).cpu.hotpluggable = 1; > > > > > > > > On Thu, Jul 16, 2020 at 6:38 PM Huacai Chen <chenhc@lemote.com> wrote: > > > > > > > > > > Now CPU#0 is not hotpluggable on MIPS, so prevent to create /sys/devices > > > > > /system/cpu/cpu0/online which confuses some user-space tools. > > > > > > What userspace tools are confused by this? They should be able to > > > handle a cpu not being able to be removed, right? > > It causes ltp's "hotplug" test fails, and ltp considers CPUs with a > > "online" node be hotpluggable. > > Is that always true? Yes, someone who meet the same problem report a bug to LTP, and LTP maintainer said that this should be fixed in kernel. Huacai
On Sat, Jul 25, 2020 at 04:29:28PM +0800, Huacai Chen wrote: > Hi, Greg, > > On Sat, Jul 25, 2020 at 3:45 PM Greg KH <gregkh@linuxfoundation.org> wrote: > > > > On Sat, Jul 25, 2020 at 02:57:31PM +0800, Huacai Chen wrote: > > > Hi Greg, > > > > > > On Sat, Jul 25, 2020 at 2:49 PM Greg KH <gregkh@linuxfoundation.org> wrote: > > > > > > > > On Sat, Jul 25, 2020 at 02:37:52PM +0800, Huacai Chen wrote: > > > > > Hi, Thomas, > > > > > > > > > > What do you think about this patch? Other archs also do the same thing > > > > > except those support hotplug CPU#0. > > > > > > > > > > grep hotpluggable arch -rwI > > > > > arch/riscv/kernel/setup.c: cpu->hotpluggable = cpu_has_hotplug(i); > > > > > arch/powerpc/kernel/sysfs.c: BUG_ON(!c->hotpluggable); > > > > > arch/powerpc/kernel/sysfs.c: c->hotpluggable = 1; > > > > > arch/powerpc/kernel/sysfs.c: if (cpu_online(cpu) || c->hotpluggable) { > > > > > arch/arm/kernel/setup.c: cpuinfo->cpu.hotpluggable = > > > > > platform_can_hotplug_cpu(cpu); > > > > > arch/sh/kernel/topology.c: c->hotpluggable = 1; > > > > > arch/ia64/kernel/topology.c: * CPEI target, then it is hotpluggable > > > > > arch/ia64/kernel/topology.c: sysfs_cpus[num].cpu.hotpluggable = 1; > > > > > arch/xtensa/kernel/setup.c: cpu->hotpluggable = !!i; > > > > > arch/s390/kernel/smp.c: c->hotpluggable = 1; > > > > > arch/mips/kernel/topology.c: c->hotpluggable = 1; > > > > > arch/arm64/kernel/cpuinfo.c: * In case the boot CPU is hotpluggable, > > > > > we record its initial state and > > > > > arch/arm64/kernel/setup.c: cpu->hotpluggable = cpu_can_disable(i); > > > > > arch/x86/kernel/topology.c: per_cpu(cpu_devices, > > > > > num).cpu.hotpluggable = 1; > > > > > > > > > > On Thu, Jul 16, 2020 at 6:38 PM Huacai Chen <chenhc@lemote.com> wrote: > > > > > > > > > > > > Now CPU#0 is not hotpluggable on MIPS, so prevent to create /sys/devices > > > > > > /system/cpu/cpu0/online which confuses some user-space tools. > > > > > > > > What userspace tools are confused by this? They should be able to > > > > handle a cpu not being able to be removed, right? > > > It causes ltp's "hotplug" test fails, and ltp considers CPUs with a > > > "online" node be hotpluggable. > > > > Is that always true? > Yes, someone who meet the same problem report a bug to LTP, and LTP > maintainer said that this should be fixed in kernel. So the action _always_ has to succeed and can never return an error? That feels wrong even for normal systems. thanks, greg k-h
在 2020/7/25 下午4:57, Greg KH 写道: > On Sat, Jul 25, 2020 at 04:29:28PM +0800, Huacai Chen wrote: >> Hi, Greg, >> >> On Sat, Jul 25, 2020 at 3:45 PM Greg KH <gregkh@linuxfoundation.org> wrote: >>> On Sat, Jul 25, 2020 at 02:57:31PM +0800, Huacai Chen wrote: >>>> Hi Greg, >>>> >>>> On Sat, Jul 25, 2020 at 2:49 PM Greg KH <gregkh@linuxfoundation.org> wrote: >>>>> On Sat, Jul 25, 2020 at 02:37:52PM +0800, Huacai Chen wrote: >>>>>> Hi, Thomas, >>>>>> >>>>>> What do you think about this patch? Other archs also do the same thing >>>>>> except those support hotplug CPU#0. >>>>>> >>>>>> grep hotpluggable arch -rwI >>>>>> arch/riscv/kernel/setup.c: cpu->hotpluggable = cpu_has_hotplug(i); >>>>>> arch/powerpc/kernel/sysfs.c: BUG_ON(!c->hotpluggable); >>>>>> arch/powerpc/kernel/sysfs.c: c->hotpluggable = 1; >>>>>> arch/powerpc/kernel/sysfs.c: if (cpu_online(cpu) || c->hotpluggable) { >>>>>> arch/arm/kernel/setup.c: cpuinfo->cpu.hotpluggable = >>>>>> platform_can_hotplug_cpu(cpu); >>>>>> arch/sh/kernel/topology.c: c->hotpluggable = 1; >>>>>> arch/ia64/kernel/topology.c: * CPEI target, then it is hotpluggable >>>>>> arch/ia64/kernel/topology.c: sysfs_cpus[num].cpu.hotpluggable = 1; >>>>>> arch/xtensa/kernel/setup.c: cpu->hotpluggable = !!i; >>>>>> arch/s390/kernel/smp.c: c->hotpluggable = 1; >>>>>> arch/mips/kernel/topology.c: c->hotpluggable = 1; >>>>>> arch/arm64/kernel/cpuinfo.c: * In case the boot CPU is hotpluggable, >>>>>> we record its initial state and >>>>>> arch/arm64/kernel/setup.c: cpu->hotpluggable = cpu_can_disable(i); >>>>>> arch/x86/kernel/topology.c: per_cpu(cpu_devices, >>>>>> num).cpu.hotpluggable = 1; >>>>>> >>>>>> On Thu, Jul 16, 2020 at 6:38 PM Huacai Chen <chenhc@lemote.com> wrote: >>>>>>> Now CPU#0 is not hotpluggable on MIPS, so prevent to create /sys/devices >>>>>>> /system/cpu/cpu0/online which confuses some user-space tools. >>>>> What userspace tools are confused by this? They should be able to >>>>> handle a cpu not being able to be removed, right? >>>> It causes ltp's "hotplug" test fails, and ltp considers CPUs with a >>>> "online" node be hotpluggable. >>> Is that always true? >> Yes, someone who meet the same problem report a bug to LTP, and LTP >> maintainer said that this should be fixed in kernel. > So the action _always_ has to succeed and can never return an error? > That feels wrong even for normal systems. If that returns error then it means kernel's hotplug function is not working as expected. Thus, LTP as a testsuit will consider the error as a indicator of malfunction kernel. Thanks - Jiaxun > > thanks, > > greg k-h
On Sat, Jul 25, 2020 at 02:37:52PM +0800, Huacai Chen wrote: > Hi, Thomas, > > What do you think about this patch? Other archs also do the same thing > except those support hotplug CPU#0. I'm ok with the patch, I'm just wondering if this is a hardware or software limitation. If it's the latter, what needs to be done to support it ? Thomas.
On Thu, Jul 16, 2020 at 06:40:23PM +0800, Huacai Chen wrote: > Now CPU#0 is not hotpluggable on MIPS, so prevent to create /sys/devices > /system/cpu/cpu0/online which confuses some user-space tools. > > Cc: stable@vger.kernel.org > Signed-off-by: Huacai Chen <chenhc@lemote.com> > --- > arch/mips/kernel/topology.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) applied to mips-next. Thomas.
在 2020/7/26 下午4:25, Thomas Bogendoerfer 写道: > On Sat, Jul 25, 2020 at 02:37:52PM +0800, Huacai Chen wrote: >> Hi, Thomas, >> >> What do you think about this patch? Other archs also do the same thing >> except those support hotplug CPU#0. > I'm ok with the patch, I'm just wondering if this is a hardware or > software limitation. If it's the latter, what needs to be done to > support it ? It should be a software limitation, x86 have already deal with that [1]. But there is no reason to spend extra effort on CPU0 hotplug. I don't think any user is expecting this feature. Thanks. [1]: https://events.static.linuxfound.org/sites/events/files/lcjpcojp13_fenghua.pdf - Jiaxun > > Thomas. >
diff --git a/arch/mips/kernel/topology.c b/arch/mips/kernel/topology.c index cd3e1f8..08ad637 100644 --- a/arch/mips/kernel/topology.c +++ b/arch/mips/kernel/topology.c @@ -20,7 +20,7 @@ static int __init topology_init(void) for_each_present_cpu(i) { struct cpu *c = &per_cpu(cpu_devices, i); - c->hotpluggable = 1; + c->hotpluggable = !!i; ret = register_cpu(c, i); if (ret) printk(KERN_WARNING "topology_init: register_cpu %d "
Now CPU#0 is not hotpluggable on MIPS, so prevent to create /sys/devices /system/cpu/cpu0/online which confuses some user-space tools. Cc: stable@vger.kernel.org Signed-off-by: Huacai Chen <chenhc@lemote.com> --- arch/mips/kernel/topology.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)