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Subject[PATCH] kernel/cpu.c: create a CPU_STARTING cpu_chain notifier
Right now, there is no notifier that is called on a new cpu, before the new
cpu begins processing interrupts/softirqs.
Various kernel function would need that notification, e.g. kvm works around
by calling smp_call_function_single(), rcu polls cpu_online_map.

The patch adds a CPU_STARTING notification. It also adds a helper function
that sends the message to all cpu_chain handlers.

Tested on x86-64.
All other archs are untested. Especially on sparc, I'm not sure if I got
it right.

Signed-Off-By: Manfred Spraul <manfred@colorfullife.com>
---
arch/alpha/kernel/smp.c | 3 +++
arch/arm/kernel/smp.c | 1 +
arch/cris/arch-v32/kernel/smp.c | 1 +
arch/ia64/kernel/smpboot.c | 1 +
arch/m32r/kernel/smpboot.c | 2 ++
arch/mips/kernel/smp.c | 2 ++
arch/powerpc/kernel/smp.c | 1 +
arch/s390/kernel/smp.c | 2 ++
arch/sh/kernel/smp.c | 2 ++
arch/sparc/kernel/sun4d_smp.c | 1 +
arch/sparc/kernel/sun4m_smp.c | 2 ++
arch/um/kernel/smp.c | 1 +
arch/x86/kernel/smpboot.c | 1 +
arch/x86/mach-voyager/voyager_smp.c | 2 ++
include/linux/cpu.h | 1 +
include/linux/notifier.h | 10 +++++++++-
kernel/cpu.c | 20 +++++++++++++++++++-
17 files changed, 51 insertions(+), 2 deletions(-)

diff --git a/arch/alpha/kernel/smp.c b/arch/alpha/kernel/smp.c
index 83df541..06b6fda 100644
--- a/arch/alpha/kernel/smp.c
+++ b/arch/alpha/kernel/smp.c
@@ -149,6 +149,9 @@ smp_callin(void)
atomic_inc(&init_mm.mm_count);
current->active_mm = &init_mm;

+ /* inform the notifiers about the new cpu */
+ notify_cpu_starting(cpuid);
+
/* Must have completely accurate bogos. */
local_irq_enable();

diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index e9842f6..e42a749 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -277,6 +277,7 @@ asmlinkage void __cpuinit secondary_start_kernel(void)
/*
* Enable local interrupts.
*/
+ notify_cpu_starting(cpu);
local_irq_enable();
local_fiq_enable();

diff --git a/arch/cris/arch-v32/kernel/smp.c b/arch/cris/arch-v32/kernel/smp.c
index 952a24b..52e16c6 100644
--- a/arch/cris/arch-v32/kernel/smp.c
+++ b/arch/cris/arch-v32/kernel/smp.c
@@ -178,6 +178,7 @@ void __init smp_callin(void)
unmask_irq(IPI_INTR_VECT);
unmask_irq(TIMER0_INTR_VECT);
preempt_disable();
+ notify_cpu_starting(cpu);
local_irq_enable();

cpu_set(cpu, cpu_online_map);
diff --git a/arch/ia64/kernel/smpboot.c b/arch/ia64/kernel/smpboot.c
index bcea81e..333b58f 100644
--- a/arch/ia64/kernel/smpboot.c
+++ b/arch/ia64/kernel/smpboot.c
@@ -401,6 +401,7 @@ smp_callin (void)
spin_lock(&vector_lock);
/* Setup the per cpu irq handling data structures */
__setup_vector_irq(cpuid);
+ notify_cpu_starting(cpuid);
cpu_set(cpuid, cpu_online_map);
per_cpu(cpu_state, cpuid) = CPU_ONLINE;
spin_unlock(&vector_lock);
diff --git a/arch/m32r/kernel/smpboot.c b/arch/m32r/kernel/smpboot.c
index 2c03ac1..fc29948 100644
--- a/arch/m32r/kernel/smpboot.c
+++ b/arch/m32r/kernel/smpboot.c
@@ -498,6 +498,8 @@ static void __init smp_online(void)
{
int cpu_id = smp_processor_id();

+ notify_cpu_starting(cpu_id);
+
local_irq_enable();

/* Get our bogomips. */
diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c
index 4410f17..7b59cfb 100644
--- a/arch/mips/kernel/smp.c
+++ b/arch/mips/kernel/smp.c
@@ -121,6 +121,8 @@ asmlinkage __cpuinit void start_secondary(void)
cpu = smp_processor_id();
cpu_data[cpu].udelay_val = loops_per_jiffy;

+ notify_cpu_starting(cpu);
+
mp_ops->smp_finish();
set_cpu_sibling_map(cpu);

diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 5337ca7..c27b10a 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -453,6 +453,7 @@ int __devinit start_secondary(void *unused)
secondary_cpu_time_init();

ipi_call_lock();
+ notify_cpu_starting(cpu);
cpu_set(cpu, cpu_online_map);
/* Update sibling maps */
base = cpu_first_thread_in_core(cpu);
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 00b9b4d..9e8b1f9 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -585,6 +585,8 @@ int __cpuinit start_secondary(void *cpuvoid)
/* Enable pfault pseudo page faults on this cpu. */
pfault_init();

+ /* call cpu notifiers */
+ notify_cpu_starting(smp_processor_id());
/* Mark this cpu as online */
spin_lock(&call_lock);
cpu_set(smp_processor_id(), cpu_online_map);
diff --git a/arch/sh/kernel/smp.c b/arch/sh/kernel/smp.c
index 60c5084..001778f 100644
--- a/arch/sh/kernel/smp.c
+++ b/arch/sh/kernel/smp.c
@@ -82,6 +82,8 @@ asmlinkage void __cpuinit start_secondary(void)

preempt_disable();

+ notify_cpu_starting(smp_processor_id());
+
local_irq_enable();

calibrate_delay();
diff --git a/arch/sparc/kernel/sun4d_smp.c b/arch/sparc/kernel/sun4d_smp.c
index 6959640..446767e 100644
--- a/arch/sparc/kernel/sun4d_smp.c
+++ b/arch/sparc/kernel/sun4d_smp.c
@@ -88,6 +88,7 @@ void __init smp4d_callin(void)
local_flush_cache_all();
local_flush_tlb_all();

+ notify_cpu_starting(cpuid);
/*
* Unblock the master CPU _only_ when the scheduler state
* of all secondary CPUs will be up-to-date, so after
diff --git a/arch/sparc/kernel/sun4m_smp.c b/arch/sparc/kernel/sun4m_smp.c
index a14a76a..9964890 100644
--- a/arch/sparc/kernel/sun4m_smp.c
+++ b/arch/sparc/kernel/sun4m_smp.c
@@ -71,6 +71,8 @@ void __cpuinit smp4m_callin(void)
local_flush_cache_all();
local_flush_tlb_all();

+ notify_cpu_starting(cpuid);
+
/* Get our local ticker going. */
smp_setup_percpu_timer();

diff --git a/arch/um/kernel/smp.c b/arch/um/kernel/smp.c
index be2d50c..0457721 100644
--- a/arch/um/kernel/smp.c
+++ b/arch/um/kernel/smp.c
@@ -85,6 +85,7 @@ static int idle_proc(void *cpup)
while (!cpu_isset(cpu, smp_commenced_mask))
cpu_relax();

+ notify_cpu_starting(cpu);
cpu_set(cpu, cpu_online_map);
default_idle();
return 0;
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 7985c5b..0b8261c 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -257,6 +257,7 @@ static void __cpuinit smp_callin(void)
end_local_APIC_setup();
map_cpu_to_logical_apicid();

+ notify_cpu_starting(cpuid);
/*
* Get our bogomips.
*
diff --git a/arch/x86/mach-voyager/voyager_smp.c b/arch/x86/mach-voyager/voyager_smp.c
index ee0fba0..199a5f4 100644
--- a/arch/x86/mach-voyager/voyager_smp.c
+++ b/arch/x86/mach-voyager/voyager_smp.c
@@ -448,6 +448,8 @@ static void __init start_secondary(void *unused)

VDEBUG(("VOYAGER SMP: CPU%d, stack at about %p\n", cpuid, &cpuid));

+ notify_cpu_starting(cpuid);
+
/* enable interrupts */
local_irq_enable();

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index d7faf88..c2747ac 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -69,6 +69,7 @@ static inline void unregister_cpu_notifier(struct notifier_block *nb)
#endif

int cpu_up(unsigned int cpu);
+void notify_cpu_starting(unsigned int cpu);
extern void cpu_hotplug_init(void);
extern void cpu_maps_update_begin(void);
extern void cpu_maps_update_done(void);
diff --git a/include/linux/notifier.h b/include/linux/notifier.h
index da2698b..8e47661 100644
--- a/include/linux/notifier.h
+++ b/include/linux/notifier.h
@@ -213,9 +213,16 @@ static inline int notifier_to_errno(int ret)
#define CPU_DOWN_FAILED 0x0006 /* CPU (unsigned)v NOT going down */
#define CPU_DEAD 0x0007 /* CPU (unsigned)v dead */
#define CPU_DYING 0x0008 /* CPU (unsigned)v not running any task,
- * not handling interrupts, soon dead */
+ * not handling interrupts, soon dead.
+ * Called on the dying cpu, interrupts
+ * are already disabled. Must not
+ * sleep, must not fail */
#define CPU_POST_DEAD 0x0009 /* CPU (unsigned)v dead, cpu_hotplug
* lock is dropped */
+#define CPU_STARTING 0x000A /* CPU (unsigned)v soon running.
+ * Called on the new cpu, just before
+ * enabling interrupts. Must not sleep,
+ * must not fail */

/* Used for CPU hotplug events occuring while tasks are frozen due to a suspend
* operation in progress
@@ -229,6 +236,7 @@ static inline int notifier_to_errno(int ret)
#define CPU_DOWN_FAILED_FROZEN (CPU_DOWN_FAILED | CPU_TASKS_FROZEN)
#define CPU_DEAD_FROZEN (CPU_DEAD | CPU_TASKS_FROZEN)
#define CPU_DYING_FROZEN (CPU_DYING | CPU_TASKS_FROZEN)
+#define CPU_STARTING_FROZEN (CPU_STARTING | CPU_TASKS_FROZEN)

/* Hibernation and suspend events */
#define PM_HIBERNATION_PREPARE 0x0001 /* Going to hibernate */
diff --git a/kernel/cpu.c b/kernel/cpu.c
index f17e985..46a8bbd 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -453,6 +453,25 @@ out:
}
#endif /* CONFIG_PM_SLEEP_SMP */

+/**
+ * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
+ * @cpu: cpu that just started
+ *
+ * This function calls the cpu_chain notifiers with CPU_STARTING.
+ * It must be called by the arch code on the new cpu, before the new cpu
+ * enables interrupts and before the "boot" cpu returns from __cpu_up().
+ */
+void notify_cpu_starting(unsigned int cpu)
+{
+ unsigned long val = CPU_STARTING;
+
+#ifdef CONFIG_PM_SLEEP_SMP
+ if (cpu_isset(cpu, frozen_cpus))
+ val = CPU_STARTING_FROZEN;
+#endif /* CONFIG_PM_SLEEP_SMP */
+ raw_notifier_call_chain(&cpu_chain, val, (void*)(long)cpu);
+}
+
#endif /* CONFIG_SMP */

/*
--
1.5.5.1

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