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Date: Wed, 16 Dec 2015 22:31:58 +1100
From: Michael Ellerman <mpe@...erman.id.au>
To: Daniel Axtens <dja@...ens.net>,
Zhang Zhuoyu <hellozzy1988@....com>, benh@...nel.crashing.org,
paulus@...ba.org, tglx@...utronix.de, jiang.liu@...ux.intel.com,
zhangzhuoyu@...s.chinamobile.com
Cc: 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 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>
>
> 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).
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)
--
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