160 lines
4.8 KiB
Diff
160 lines
4.8 KiB
Diff
From 8e48945ae26991b40973b233f34937477dcf97ab Mon Sep 17 00:00:00 2001
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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Date: Fri, 31 Jan 2014 14:20:31 +0100
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Subject: [PATCH 1/7] irq_work: allow certain work in hard irq context
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/3.14/patches-3.14.10-rt7.tar.xz
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irq_work is processed in softirq context on -RT because we want to avoid
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long latencies which might arise from processing lots of perf events.
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The noHZ-full mode requires its callback to be called from real hardirq
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context (commit 76c24fb ("nohz: New APIs to re-evaluate the tick on full
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dynticks CPUs")). If it is called from a thread context we might get
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wrong results for checks like "is_idle_task(current)".
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This patch introduces a second list (hirq_work_list) which will be used
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if irq_work_run() has been invoked from hardirq context and process only
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work items marked with IRQ_WORK_HARD_IRQ.
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This patch also removes arch_irq_work_raise() from sparc & powerpc like
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it is already done for x86. Atleast for powerpc it is somehow
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superfluous because it is called from the timer interrupt which should
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invoke update_process_times().
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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arch/arm/kernel/smp.c | 2 ++
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arch/powerpc/kernel/time.c | 2 +-
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arch/sparc/kernel/pcr.c | 2 ++
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include/linux/irq_work.h | 1 +
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kernel/irq_work.c | 22 +++++++++++++++++++---
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kernel/time/tick-sched.c | 1 +
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kernel/timer.c | 2 +-
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7 files changed, 27 insertions(+), 5 deletions(-)
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--- a/arch/arm/kernel/smp.c
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+++ b/arch/arm/kernel/smp.c
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@@ -454,12 +454,14 @@ void arch_send_call_function_single_ipi(
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}
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#ifdef CONFIG_IRQ_WORK
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+#ifndef CONFIG_PREEMPT_RT_FULL
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void arch_irq_work_raise(void)
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{
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if (is_smp())
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smp_cross_call(cpumask_of(smp_processor_id()), IPI_IRQ_WORK);
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}
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#endif
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+#endif
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static const char *ipi_types[NR_IPI] = {
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#define S(x,s) [x] = s
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--- a/arch/powerpc/kernel/time.c
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+++ b/arch/powerpc/kernel/time.c
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@@ -423,7 +423,7 @@ unsigned long profile_pc(struct pt_regs
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EXPORT_SYMBOL(profile_pc);
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#endif
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-#ifdef CONFIG_IRQ_WORK
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+#if defined(CONFIG_IRQ_WORK) && !defined(CONFIG_PREEMPT_RT_FULL)
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/*
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* 64-bit uses a byte in the PACA, 32-bit uses a per-cpu variable...
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--- a/arch/sparc/kernel/pcr.c
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+++ b/arch/sparc/kernel/pcr.c
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@@ -43,10 +43,12 @@ void __irq_entry deferred_pcr_work_irq(i
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set_irq_regs(old_regs);
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}
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+#ifndef CONFIG_PREEMPT_RT_FULL
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void arch_irq_work_raise(void)
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{
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set_softint(1 << PIL_DEFERRED_PCR_WORK);
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}
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+#endif
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const struct pcr_ops *pcr_ops;
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EXPORT_SYMBOL_GPL(pcr_ops);
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--- a/include/linux/irq_work.h
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+++ b/include/linux/irq_work.h
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@@ -16,6 +16,7 @@
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#define IRQ_WORK_BUSY 2UL
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#define IRQ_WORK_FLAGS 3UL
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#define IRQ_WORK_LAZY 4UL /* Doesn't want IPI, wait for tick */
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+#define IRQ_WORK_HARD_IRQ 8UL /* Run hard IRQ context, even on RT */
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struct irq_work {
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unsigned long flags;
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--- a/kernel/irq_work.c
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+++ b/kernel/irq_work.c
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@@ -20,6 +20,9 @@
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static DEFINE_PER_CPU(struct llist_head, irq_work_list);
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+#ifdef CONFIG_PREEMPT_RT_FULL
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+static DEFINE_PER_CPU(struct llist_head, hirq_work_list);
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+#endif
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static DEFINE_PER_CPU(int, irq_work_raised);
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/*
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@@ -48,7 +51,11 @@ static bool irq_work_claim(struct irq_wo
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return true;
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}
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+#ifdef CONFIG_PREEMPT_RT_FULL
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+void arch_irq_work_raise(void)
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+#else
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void __weak arch_irq_work_raise(void)
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+#endif
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{
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/*
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* Lame architectures will get the timer tick callback
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@@ -70,8 +77,12 @@ void irq_work_queue(struct irq_work *wor
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/* Queue the entry and raise the IPI if needed. */
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preempt_disable();
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- llist_add(&work->llnode, &__get_cpu_var(irq_work_list));
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-
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+#ifdef CONFIG_PREEMPT_RT_FULL
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+ if (work->flags & IRQ_WORK_HARD_IRQ)
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+ llist_add(&work->llnode, &__get_cpu_var(hirq_work_list));
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+ else
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+#endif
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+ llist_add(&work->llnode, &__get_cpu_var(irq_work_list));
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/*
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* If the work is not "lazy" or the tick is stopped, raise the irq
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* work interrupt (if supported by the arch), otherwise, just wait
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@@ -115,7 +126,12 @@ static void __irq_work_run(void)
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__this_cpu_write(irq_work_raised, 0);
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barrier();
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- this_list = &__get_cpu_var(irq_work_list);
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+#ifdef CONFIG_PREEMPT_RT_FULL
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+ if (in_irq())
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+ this_list = &__get_cpu_var(hirq_work_list);
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+ else
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+#endif
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+ this_list = &__get_cpu_var(irq_work_list);
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if (llist_empty(this_list))
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return;
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--- a/kernel/time/tick-sched.c
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+++ b/kernel/time/tick-sched.c
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@@ -222,6 +222,7 @@ static void nohz_full_kick_work_func(str
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static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) = {
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.func = nohz_full_kick_work_func,
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+ .flags = IRQ_WORK_HARD_IRQ,
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};
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/*
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--- a/kernel/timer.c
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+++ b/kernel/timer.c
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@@ -1425,7 +1425,7 @@ void update_process_times(int user_tick)
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scheduler_tick();
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run_local_timers();
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rcu_check_callbacks(cpu, user_tick);
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-#if defined(CONFIG_IRQ_WORK) && !defined(CONFIG_PREEMPT_RT_FULL)
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+#if defined(CONFIG_IRQ_WORK)
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if (in_irq())
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irq_work_run();
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#endif
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