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Date: Thu, 24 Dec 2015 15:05:43 +0800
From: "Zhang Zhuoyu" <zhangzhuoyu@...s.chinamobile.com>
To: "'Denis Kirjanov'" <kda@...ux-powerpc.org>
Cc: "'Michael Ellerman'" <mpe@...erman.id.au>,
<linux-kernel@...r.kernel.org>, <paulus@...ba.org>,
<tglx@...utronix.de>, <linuxppc-dev@...ts.ozlabs.org>,
<jiang.liu@...ux.intel.com>, "'Daniel Axtens'" <dja@...ens.net>
Subject: RE: [PATCH 1/1] powerpc/irq: tidy up inconsistent context in migrate_irqs()
> -----Original Message-----
> From: Denis Kirjanov [mailto:kda@...ux-powerpc.org]
> Sent: Thursday, December 24, 2015 6:04 AM
> To: Zhang Zhuoyu <zhangzhuoyu@...s.chinamobile.com>
> Cc: Michael Ellerman <mpe@...erman.id.au>; linux-kernel@...r.kernel.org;
> paulus@...ba.org; tglx@...utronix.de; linuxppc-dev@...ts.ozlabs.org;
> jiang.liu@...ux.intel.com; Daniel Axtens <dja@...ens.net>
> Subject: Re: [PATCH 1/1] powerpc/irq: tidy up inconsistent context in
> migrate_irqs()
>
> On 12/24/15, Denis Kirjanov <kda@...ux-powerpc.org> wrote:
> > On 12/23/15, Zhang Zhuoyu <zhangzhuoyu@...s.chinamobile.com> wrote:
> >> Hi, Denis
> >>
> >> Any test result on pmac machine for this patch?
> >
> > Hi,
> >
> > So I ran the tests by writing to cpuN/online.
> >
> > with your change I'm observing lines like the following:
> > [ 713.436922] NOHZ: local_softirq_pending 08
>
Hi,
It is a NOHZ warning, NOHZ will check for whether there are softirqs pending when an online CPU goes
idle, this warning cannot be triggered by offlining CPU, you should check which driver's
softirq is preventing CPU goes idle.
> Another bad thing that the current powerpc/next kernel crashed on pmac
> (without this change) while enabling/disabling cpu cores :/ I've attached the
> screenshot
>
>
> >
> > Thanks!
> >
> >>
> >> Zhuoyu
> >>
> >>> -----Original Message-----
> >>> From: Zhang Zhuoyu [mailto:zhangzhuoyu@...s.chinamobile.com]
> >>> Sent: Wednesday, December 16, 2015 10:46 PM
> >>> To: 'Denis Kirjanov'; 'Michael Ellerman'
> >>> Cc: 'Daniel Axtens'; 'Zhang Zhuoyu'; 'benh@...nel.crashing.org';
> >>> 'paulus@...ba.org'; 'tglx@...utronix.de';
> >>> 'jiang.liu@...ux.intel.com'; 'linuxppc-dev@...ts.ozlabs.org'; 'linux-
> kernel@...r.kernel.org'
> >>> Subject: RE: [PATCH 1/1] powerpc/irq: tidy up inconsistent context
> >>> in
> >>> migrate_irqs()
> >>>
> >>>
> >>> > -----Original Message-----
> >>> > From: Denis Kirjanov [mailto:kda@...ux-powerpc.org]
> >>> > Sent: Wednesday, December 16, 2015 7:55 PM
> >>> > To: Michael Ellerman
> >>> > Cc: Daniel Axtens; Zhang Zhuoyu; benh@...nel.crashing.org;
> >>> > paulus@...ba.org; tglx@...utronix.de; jiang.liu@...ux.intel.com;
> >>> > zhangzhuoyu@...s.chinamobile.com; linuxppc-dev@...ts.ozlabs.org;
> >>> > linux- kernel@...r.kernel.org
> >>> > Subject: Re: [PATCH 1/1] powerpc/irq: tidy up inconsistent context
> >>> > in
> >>> > migrate_irqs()
> >>> >
> >>> > On 12/16/15, Michael Ellerman <mpe@...erman.id.au> wrote:
> >>> > > On Wed, 2015-12-16 at 17:08 +1100, Daniel Axtens wrote:
> >>> > >> Hi,
> >>> > >>
> >>> > >> A couple of things.
> >>> > >>
> >>> > >> Firstly, your two email addresses don't match:
> >>> > >>
> >>> > >> Zhang Zhuoyu <hellozzy1988@....com> writes:
> >>> > >
> >>> > >> > From: Zhang Zhuoyu <zhangzhuoyu@...s.chinamobile.com>
> >>> > >>
> >>>
> >>> Mmm, My mistake, I will correct it next time.
> >>>
> >>> > >> These lines do seem odd! Are they causing a problem?
> >>> > >>
> >>> > >> I'd be more comfortable removing them if I understood why they
> >>> > >> were added. But they've been around since the beginning of git
> >>> > >> history so that could be a bit difficult.
> >>> > >
> >>> > > It's in the fullhist tree, but that doesn't tell us much (below,
> >>> > > named fixup_irqs()).
> >>> > >
> >>> > > But I suspect those lines are actually there very deliberately.
> >>> > >
> >>> > > The function is migrating interrupts off the recently offlined
> >>> > > cpu, because we don't want to take interrupts on an offline cpu.
> >>> > >
> >>> > > After it's finished doing the migration, it wants to make sure
> >>> > > there are no interrupts that have already been latched by the offline
> cpu.
> >>> > > So it briefly enables interrupts, waits a bit for the interrupts
> >>> > > to fire, and the disables them again.
> >>> > >
> >>> > > Whether that actually works I couldn't say, it is very old code,
> >>> > > and it's used on platforms where I don't ever test cpu hotplug
> >>> > > (85xx & powermac).
> >>> >
> >>> > Yeah, it would be nice to test this change. I'll try it on my
> >>> > quad-core pmac machine
> >>> >
> >>>
> >>> Thanks Michael for help explaining the code logic, it also resolved
> >>> my doubts.
> >>> These snippets are suspected when I did PM benchmark on FSL
> MPC85xx
> >>> series(T1040, T4240), For T4240, which has 24 CPUs, it waits 1ms in
> >>> migrate_irqs()each time a CPU is plugged offline, it seems a waste
> >>> of time. I also did a test on T1040, after plugging offline/online
> >>> CPU hundreds of times, system works well. If you have any other
> >>> suggestion on how to test, I'd like to do more benchmark.
> >>> (1)for((i=0; i<1000; i++)); do echo 0 >
> >>> /sys/devices/system/cpu/cpu1/online;
> >>> sleep 1; echo 1 > /sys/devices/system/cpu/cpu1/online; done
> >>> (2)root@...40rdb:~# cat /proc/interrupts
> >>> CPU0 CPU1 CPU2 CPU3
> >>> 36: 393 1 223 1 OpenPIC 36 Level
> >>> serial
> >>> LOC: 1946 1486 1555 1361 Local timer
> >>> interrupts
> >>> DBL: 7371 9707 9390 7568 Doorbell interrupts
> >>> (3)root@...40rdb:~# ps
> >>> PID TTY TIME CMD
> >>> 2751 ttyS0 00:00:00 sh
> >>> 2757 ttyS0 00:00:00 ps
> >>> root@...40rdb:~# taskset -pc 1 2751
> >>> pid 2751's current affinity list: 0-3 pid 2751's new affinity list:
> >>> 1 root@...40rdb:~# root@...40rdb:~# root@...40rdb:~#
> >>> root@...40rdb:~# echo "hello"
> >>> hello
> >>> root@...40rdb:~#
> >>>
> >>> > >
> >>> > > cheers
> >>> > >
> >>> > >
> >>> > > commit d58830b9a740ad1c3b089196d4afdaea251dc701
> >>> > > Author: Zwane Mwaikambo <zwane@....linux.org.uk>
> >>> > > Date: Fri Mar 4 17:34:00 2005 -0800
> >>> > >
> >>> > > [PATCH] ppc64: generic hotplug cpu support
> >>> > >
> >>> > > Patch provides a generic hotplug cpu implementation, with
> >>> > > the only current
> >>> > > user being pmac. This doesn't replace real hotplug code as
> >>> > > is currently
> >>> > > used by LPAR systems. Ben i can add the additional pmac
> >>> > > specific code to
> >>> > > put the processor into a sleeping state seperately. Thanks
> >>> > > to Nathan for
> >>> > > testing.
> >>> > >
> >>> > > Signed-off-by: Zwane Mwaikambo <zwane@....linux.org.uk>
> >>> > > Signed-off-by: Andrew Morton <akpm@...l.org>
> >>> > > Signed-off-by: Linus Torvalds <torvalds@...l.org>
> >>> > >
> >>> > > diff --git a/arch/ppc64/Kconfig b/arch/ppc64/Kconfig index
> >>> > > a7933ab62e98..861f4460ad02 100644
> >>> > > --- a/arch/ppc64/Kconfig
> >>> > > +++ b/arch/ppc64/Kconfig
> >>> > > @@ -313,7 +313,7 @@ source "drivers/pci/Kconfig"
> >>> > >
> >>> > > config HOTPLUG_CPU
> >>> > > bool "Support for hot-pluggable CPUs"
> >>> > > - depends on SMP && EXPERIMENTAL && PPC_PSERIES
> >>> > > + depends on SMP && EXPERIMENTAL && (PPC_PSERIES ||
> >>> > PPC_PMAC)
> >>> > > select HOTPLUG
> >>> > > ---help---
> >>> > > Say Y here to be able to turn CPUs off and on.
> >>> > > diff --git a/arch/ppc64/kernel/idle.c b/arch/ppc64/kernel/idle.c
> >>> > > index 398b4682127b..51eb6af14a8f 100644
> >>> > > --- a/arch/ppc64/kernel/idle.c
> >>> > > +++ b/arch/ppc64/kernel/idle.c
> >>> > > @@ -293,6 +293,10 @@ static int native_idle(void)
> >>> > > power4_idle();
> >>> > > if (need_resched())
> >>> > > schedule();
> >>> > > +
> >>> > > + if (cpu_is_offline(smp_processor_id()) &&
> >>> > > + system_state == SYSTEM_RUNNING)
> >>> > > + cpu_die();
> >>> > > }
> >>> > > return 0;
> >>> > > }
> >>> > > diff --git a/arch/ppc64/kernel/irq.c b/arch/ppc64/kernel/irq.c
> >>> > > index
> >>> > > 0ea8016146a2..4fd7f203c1e3 100644
> >>> > > --- a/arch/ppc64/kernel/irq.c
> >>> > > +++ b/arch/ppc64/kernel/irq.c
> >>> > > @@ -116,6 +116,35 @@ skip:
> >>> > > return 0;
> >>> > > }
> >>> > >
> >>> > > +#ifdef CONFIG_HOTPLUG_CPU
> >>> > > +void fixup_irqs(cpumask_t map)
> >>> > > +{
> >>> > > + unsigned int irq;
> >>> > > + static int warned;
> >>> > > +
> >>> > > + for_each_irq(irq) {
> >>> > > + cpumask_t mask;
> >>> > > +
> >>> > > + if (irq_desc[irq].status & IRQ_PER_CPU)
> >>> > > + continue;
> >>> > > +
> >>> > > + cpus_and(mask, irq_affinity[irq], map);
> >>> > > + if (any_online_cpu(mask) == NR_CPUS) {
> >>> > > + printk("Breaking affinity for irq %i\n", irq);
> >>> > > + mask = map;
> >>> > > + }
> >>> > > + if (irq_desc[irq].handler->set_affinity)
> >>> > > + irq_desc[irq].handler->set_affinity(irq, mask);
> >>> > > + else if (irq_desc[irq].action && !(warned++))
> >>> > > + printk("Cannot set affinity for irq %i\n", irq);
> >>> > > + }
> >>> > > +
> >>> > > + local_irq_enable();
> >>> > > + mdelay(1);
> >>> > > + local_irq_disable();
> >>> > > +}
> >>> > > +#endif
> >>> > > +
> >>> > > extern int noirqdebug;
> >>> > >
> >>> > > /*
> >>> > > diff --git a/arch/ppc64/kernel/pSeries_setup.c
> >>> > > b/arch/ppc64/kernel/pSeries_setup.c
> >>> > > index f603397b7b04..0426892749c6 100644
> >>> > > --- a/arch/ppc64/kernel/pSeries_setup.c
> >>> > > +++ b/arch/ppc64/kernel/pSeries_setup.c
> >>> > > @@ -320,8 +320,9 @@ static void __init pSeries_discover_pic(void)
> >>> > > }
> >>> > > }
> >>> > >
> >>> > > -static void pSeries_cpu_die(void)
> >>> > > +static void pSeries_mach_cpu_die(void)
> >>> > > {
> >>> > > + idle_task_exit();
> >>> > > local_irq_disable();
> >>> > > /* Some hardware requires clearing the CPPR, while other
> >>> > > hardware
> >>> > does not
> >>> > > * it is safe either way
> >>> > > @@ -599,7 +600,7 @@ struct machdep_calls __initdata pSeries_md =
> {
> >>> > > .power_off = rtas_power_off,
> >>> > > .halt = rtas_halt,
> >>> > > .panic = rtas_os_term,
> >>> > > - .cpu_die = pSeries_cpu_die,
> >>> > > + .cpu_die = pSeries_mach_cpu_die,
> >>> > > .get_boot_time = pSeries_get_boot_time,
> >>> > > .get_rtc_time = pSeries_get_rtc_time,
> >>> > > .set_rtc_time = pSeries_set_rtc_time,
> >>> > > diff --git a/arch/ppc64/kernel/pmac_setup.c
> >>> > > b/arch/ppc64/kernel/pmac_setup.c index
> >>> > > 41fa6e95a06f..5c56fc956245
> >>> > > 100644
> >>> > > --- a/arch/ppc64/kernel/pmac_setup.c
> >>> > > +++ b/arch/ppc64/kernel/pmac_setup.c
> >>> > > @@ -439,6 +439,9 @@ static int __init pmac_probe(int platform)
> >>> > > }
> >>> > >
> >>> > > struct machdep_calls __initdata pmac_md = {
> >>> > > +#ifdef CONFIG_HOTPLUG_CPU
> >>> > > + .cpu_die = generic_mach_cpu_die,
> >>> > > +#endif
> >>> > > .probe = pmac_probe,
> >>> > > .setup_arch = pmac_setup_arch,
> >>> > > .init_early = pmac_init_early,
> >>> > > diff --git a/arch/ppc64/kernel/pmac_smp.c
> >>> > > b/arch/ppc64/kernel/pmac_smp.c index
> e0b37079943c..c27588ede2fe
> >>> > 100644
> >>> > > --- a/arch/ppc64/kernel/pmac_smp.c
> >>> > > +++ b/arch/ppc64/kernel/pmac_smp.c
> >>> > > @@ -308,4 +308,9 @@ struct smp_ops_t core99_smp_ops
> __pmacdata =
> >>> {
> >>> > > void __init pmac_setup_smp(void) {
> >>> > > smp_ops = &core99_smp_ops;
> >>> > > +#ifdef CONFIG_HOTPLUG_CPU
> >>> > > + smp_ops->cpu_enable = generic_cpu_enable;
> >>> > > + smp_ops->cpu_disable = generic_cpu_disable;
> >>> > > + smp_ops->cpu_die = generic_cpu_die; #endif
> >>> > > }
> >>> > > diff --git a/arch/ppc64/kernel/setup.c
> >>> > > b/arch/ppc64/kernel/setup.c index d98c320828e5..078c3551ce8a
> >>> > > 100644
> >>> > > --- a/arch/ppc64/kernel/setup.c
> >>> > > +++ b/arch/ppc64/kernel/setup.c
> >>> > > @@ -1377,9 +1377,6 @@ early_param("xmon", early_xmon);
> >>> > >
> >>> > > void cpu_die(void)
> >>> > > {
> >>> > > - idle_task_exit();
> >>> > > if (ppc_md.cpu_die)
> >>> > > ppc_md.cpu_die();
> >>> > > - local_irq_disable();
> >>> > > - for (;;);
> >>> > > }
> >>> > > diff --git a/arch/ppc64/kernel/smp.c b/arch/ppc64/kernel/smp.c
> >>> > > index
> >>> > > a9e43792f8fe..cde1947432a1 100644
> >>> > > --- a/arch/ppc64/kernel/smp.c
> >>> > > +++ b/arch/ppc64/kernel/smp.c
> >>> > > @@ -30,6 +30,7 @@
> >>> > > #include <linux/err.h>
> >>> > > #include <linux/sysdev.h>
> >>> > > #include <linux/cpu.h>
> >>> > > +#include <linux/notifier.h>
> >>> > >
> >>> > > #include <asm/ptrace.h>
> >>> > > #include <asm/atomic.h>
> >>> > > @@ -406,10 +407,89 @@ void __devinit
> smp_prepare_boot_cpu(void)
> >>> > > current_set[boot_cpuid] = current->thread_info; }
> >>> > >
> >>> > > +#ifdef CONFIG_HOTPLUG_CPU
> >>> > > +/* State of each CPU during hotplug phases */
> >>> > > +DEFINE_PER_CPU(int,
> >>> > > +cpu_state) = { 0 };
> >>> > > +
> >>> > > +int generic_cpu_disable(void)
> >>> > > +{
> >>> > > + unsigned int cpu = smp_processor_id();
> >>> > > +
> >>> > > + if (cpu == boot_cpuid)
> >>> > > + return -EBUSY;
> >>> > > +
> >>> > > + systemcfg->processorCount--;
> >>> > > + cpu_clear(cpu, cpu_online_map);
> >>> > > + fixup_irqs(cpu_online_map);
> >>> > > + return 0;
> >>> > > +}
> >>> > > +
> >>> > > +int generic_cpu_enable(unsigned int cpu) {
> >>> > > + /* Do the normal bootup if we haven't
> >>> > > + * already bootstrapped. */
> >>> > > + if (system_state != SYSTEM_RUNNING)
> >>> > > + return -ENOSYS;
> >>> > > +
> >>> > > + /* get the target out of it's holding state */
> >>> > > + per_cpu(cpu_state, cpu) = CPU_UP_PREPARE;
> >>> > > + wmb();
> >>> > > +
> >>> > > + while (!cpu_online(cpu))
> >>> > > + cpu_relax();
> >>> > > +
> >>> > > + fixup_irqs(cpu_online_map);
> >>> > > + /* counter the irq disable in fixup_irqs */
> >>> > > + local_irq_enable();
> >>> > > + return 0;
> >>> > > +}
> >>> > > +
> >>> > > +void generic_cpu_die(unsigned int cpu) {
> >>> > > + int i;
> >>> > > +
> >>> > > + for (i = 0; i < 100; i++) {
> >>> > > + rmb();
> >>> > > + if (per_cpu(cpu_state, cpu) == CPU_DEAD)
> >>> > > + return;
> >>> > > + msleep(100);
> >>> > > + }
> >>> > > + printk(KERN_ERR "CPU%d didn't die...\n", cpu); }
> >>> > > +
> >>> > > +void generic_mach_cpu_die(void) {
> >>> > > + unsigned int cpu;
> >>> > > +
> >>> > > + local_irq_disable();
> >>> > > + cpu = smp_processor_id();
> >>> > > + printk(KERN_DEBUG "CPU%d offline\n", cpu);
> >>> > > + __get_cpu_var(cpu_state) = CPU_DEAD;
> >>> > > + wmb();
> >>> > > + while (__get_cpu_var(cpu_state) != CPU_UP_PREPARE)
> >>> > > + cpu_relax();
> >>> > > +
> >>> > > + flush_tlb_pending();
> >>> > > + cpu_set(cpu, cpu_online_map);
> >>> > > + local_irq_enable();
> >>> > > +}
> >>> > > +#endif
> >>> > > +
> >>> > > +static int __devinit cpu_enable(unsigned int cpu) {
> >>> > > + if (smp_ops->cpu_enable)
> >>> > > + return smp_ops->cpu_enable(cpu);
> >>> > > +
> >>> > > + return -ENOSYS;
> >>> > > +}
> >>> > > +
> >>> > > int __devinit __cpu_up(unsigned int cpu) {
> >>> > > int c;
> >>> > >
> >>> > > + if (!cpu_enable(cpu))
> >>> > > + return 0;
> >>> > > +
> >>> > > /* At boot, don't bother with non-present cpus -JSCHOPP */
> >>> > > if (system_state < SYSTEM_RUNNING && !cpu_present(cpu))
> >>> > > return -ENOENT;
> >>> > > diff --git a/arch/ppc64/kernel/sysfs.c
> >>> > > b/arch/ppc64/kernel/sysfs.c index bbc9dcda17f7..0925694c3ce5
> >>> > > 100644
> >>> > > --- a/arch/ppc64/kernel/sysfs.c
> >>> > > +++ b/arch/ppc64/kernel/sysfs.c
> >>> > > @@ -18,7 +18,7 @@
> >>> > > #include <asm/systemcfg.h>
> >>> > > #include <asm/paca.h>
> >>> > > #include <asm/lppaca.h>
> >>> > > -
> >>> > > +#include <asm/machdep.h>
> >>> > >
> >>> > > static DEFINE_PER_CPU(struct cpu, cpu_devices);
> >>> > >
> >>> > > @@ -413,9 +413,7 @@ static int __init topology_init(void)
> >>> > > * CPU. For instance, the boot cpu might never be
> valid
> >>> > > * for hotplugging.
> >>> > > */
> >>> > > -#ifdef CONFIG_HOTPLUG_CPU
> >>> > > - if (systemcfg->platform != PLATFORM_PSERIES_LPAR)
> >>> > > -#endif
> >>> > > + if (!ppc_md.cpu_die)
> >>> > > c->no_control = 1;
> >>> > >
> >>> > > if (cpu_online(cpu) || (c->no_control == 0)) { diff --git
> >>> > > a/include/asm-ppc64/machdep.h b/include/asm-ppc64/machdep.h
> >>> index
> >>> > > 476d2185ffd1..03fe499c7604 100644
> >>> > > --- a/include/asm-ppc64/machdep.h
> >>> > > +++ b/include/asm-ppc64/machdep.h
> >>> > > @@ -30,6 +30,7 @@ struct smp_ops_t {
> >>> > > void (*setup_cpu)(int nr);
> >>> > > void (*take_timebase)(void);
> >>> > > void (*give_timebase)(void);
> >>> > > + int (*cpu_enable)(unsigned int nr);
> >>> > > int (*cpu_disable)(void);
> >>> > > void (*cpu_die)(unsigned int nr); }; diff --git
> >>> > > a/include/asm-ppc64/smp.h b/include/asm-ppc64/smp.h index
> >>> > > 965980bbbb57..c8646fa999c2 100644
> >>> > > --- a/include/asm-ppc64/smp.h
> >>> > > +++ b/include/asm-ppc64/smp.h
> >>> > > @@ -29,7 +29,7 @@
> >>> > > extern int boot_cpuid;
> >>> > > extern int boot_cpuid_phys;
> >>> > >
> >>> > > -extern void cpu_die(void) __attribute__((noreturn));
> >>> > > +extern void cpu_die(void);
> >>> > >
> >>> > > #ifdef CONFIG_SMP
> >>> > >
> >>> > > @@ -37,6 +37,13 @@ extern void smp_send_debugger_break(int
> cpu);
> >>> > > struct pt_regs; extern void smp_message_recv(int, struct
> >>> > > pt_regs *);
> >>> > >
> >>> > > +#ifdef CONFIG_HOTPLUG_CPU
> >>> > > +extern void fixup_irqs(cpumask_t map); int
> >>> > > +generic_cpu_disable(void); int generic_cpu_enable(unsigned int
> >>> > > +cpu); void generic_cpu_die(unsigned int cpu); void
> >>> > > +generic_mach_cpu_die(void); #endif
> >>> > >
> >>> > > #define __smp_processor_id() (get_paca()->paca_index) #define
> >>> > > hard_smp_processor_id() (get_paca()->hw_cpu_id)
> >>> > >
> >>> > > _______________________________________________
> >>> > > Linuxppc-dev mailing list
> >>> > > Linuxppc-dev@...ts.ozlabs.org
> >>> > > https://lists.ozlabs.org/listinfo/linuxppc-dev
> >>
> >>
> >>
> >> _______________________________________________
> >> Linuxppc-dev mailing list
> >> Linuxppc-dev@...ts.ozlabs.org
> >> https://lists.ozlabs.org/listinfo/linuxppc-dev
> >
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