121 lines
3.5 KiB
Diff
121 lines
3.5 KiB
Diff
From 32d07c91c3f116cf5dd6e5326d978018d48615d5 Mon Sep 17 00:00:00 2001
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Message-Id: <32d07c91c3f116cf5dd6e5326d978018d48615d5.1601675152.git.zanussi@kernel.org>
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In-Reply-To: <5b5a156f9808b1acf1205606e03da117214549ea.1601675151.git.zanussi@kernel.org>
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References: <5b5a156f9808b1acf1205606e03da117214549ea.1601675151.git.zanussi@kernel.org>
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From: Thomas Gleixner <tglx@linutronix.de>
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Date: Wed, 19 Jul 2017 17:31:20 +0200
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Subject: [PATCH 228/333] cpu/hotplug: Implement CPU pinning
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.148-rt64.tar.xz
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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---
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include/linux/sched.h | 1 +
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kernel/cpu.c | 38 ++++++++++++++++++++++++++++++++++++++
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2 files changed, 39 insertions(+)
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diff --git a/include/linux/sched.h b/include/linux/sched.h
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index f18668e166f2..ff1fe0b3c1e3 100644
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--- a/include/linux/sched.h
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+++ b/include/linux/sched.h
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@@ -671,6 +671,7 @@ struct task_struct {
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#if defined(CONFIG_SMP) && defined(CONFIG_PREEMPT_RT_BASE)
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int migrate_disable;
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int migrate_disable_update;
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+ int pinned_on_cpu;
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# ifdef CONFIG_SCHED_DEBUG
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int migrate_disable_atomic;
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# endif
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diff --git a/kernel/cpu.c b/kernel/cpu.c
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index 267fcad3a81e..f9e0e3db440a 100644
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--- a/kernel/cpu.c
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+++ b/kernel/cpu.c
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@@ -76,6 +76,11 @@ static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state) = {
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.fail = CPUHP_INVALID,
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};
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+#ifdef CONFIG_HOTPLUG_CPU
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+static DEFINE_PER_CPU(struct rt_rw_lock, cpuhp_pin_lock) = \
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+ __RWLOCK_RT_INITIALIZER(cpuhp_pin_lock);
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+#endif
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+
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#if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP)
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static struct lockdep_map cpuhp_state_up_map =
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STATIC_LOCKDEP_MAP_INIT("cpuhp_state-up", &cpuhp_state_up_map);
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@@ -287,7 +292,28 @@ static int cpu_hotplug_disabled;
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*/
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void pin_current_cpu(void)
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{
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+ struct rt_rw_lock *cpuhp_pin;
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+ unsigned int cpu;
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+ int ret;
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+
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+again:
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+ cpuhp_pin = this_cpu_ptr(&cpuhp_pin_lock);
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+ ret = __read_rt_trylock(cpuhp_pin);
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+ if (ret) {
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+ current->pinned_on_cpu = smp_processor_id();
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+ return;
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+ }
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+ cpu = smp_processor_id();
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+ preempt_enable();
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+
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+ __read_rt_lock(cpuhp_pin);
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+ preempt_disable();
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+ if (cpu != smp_processor_id()) {
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+ __read_rt_unlock(cpuhp_pin);
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+ goto again;
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+ }
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+ current->pinned_on_cpu = cpu;
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}
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/**
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@@ -295,6 +321,13 @@ void pin_current_cpu(void)
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*/
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void unpin_current_cpu(void)
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{
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+ struct rt_rw_lock *cpuhp_pin = this_cpu_ptr(&cpuhp_pin_lock);
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+
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+ if (WARN_ON(current->pinned_on_cpu != smp_processor_id()))
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+ cpuhp_pin = per_cpu_ptr(&cpuhp_pin_lock, current->pinned_on_cpu);
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+
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+ current->pinned_on_cpu = -1;
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+ __read_rt_unlock(cpuhp_pin);
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}
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DEFINE_STATIC_PERCPU_RWSEM(cpu_hotplug_lock);
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@@ -869,6 +902,7 @@ static int take_cpu_down(void *_param)
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static int takedown_cpu(unsigned int cpu)
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{
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+ struct rt_rw_lock *cpuhp_pin = per_cpu_ptr(&cpuhp_pin_lock, cpu);
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struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
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int err;
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@@ -881,11 +915,14 @@ static int takedown_cpu(unsigned int cpu)
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*/
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irq_lock_sparse();
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+ __write_rt_lock(cpuhp_pin);
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+
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/*
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* So now all preempt/rcu users must observe !cpu_active().
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*/
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err = stop_machine_cpuslocked(take_cpu_down, NULL, cpumask_of(cpu));
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if (err) {
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+ __write_rt_unlock(cpuhp_pin);
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/* CPU refused to die */
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irq_unlock_sparse();
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/* Unpark the hotplug thread so we can rollback there */
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@@ -904,6 +941,7 @@ static int takedown_cpu(unsigned int cpu)
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wait_for_ap_thread(st, false);
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BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
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+ __write_rt_unlock(cpuhp_pin);
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/* Interrupts are moved away from the dying cpu, reenable alloc/free */
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irq_unlock_sparse();
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--
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2.17.1
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