129 lines
3.6 KiB
Diff
129 lines
3.6 KiB
Diff
Subject: sched: Move mmdrop to RCU on RT
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From: Thomas Gleixner <tglx@linutronix.de>
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Date: Mon, 06 Jun 2011 12:20:33 +0200
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.11/older/patches-4.11.5-rt1.tar.xz
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Takes sleeping locks and calls into the memory allocator, so nothing
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we want to do in task switch and oder atomic contexts.
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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---
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include/linux/mm_types.h | 4 ++++
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include/linux/sched/mm.h | 11 +++++++++++
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kernel/fork.c | 13 +++++++++++++
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kernel/sched/core.c | 19 +++++++++++++++++--
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4 files changed, 45 insertions(+), 2 deletions(-)
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--- a/include/linux/mm_types.h
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+++ b/include/linux/mm_types.h
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@@ -11,6 +11,7 @@
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#include <linux/completion.h>
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#include <linux/cpumask.h>
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#include <linux/uprobes.h>
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+#include <linux/rcupdate.h>
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#include <linux/page-flags-layout.h>
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#include <linux/workqueue.h>
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@@ -491,6 +492,9 @@ struct mm_struct {
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bool tlb_flush_pending;
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#endif
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struct uprobes_state uprobes_state;
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+#ifdef CONFIG_PREEMPT_RT_BASE
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+ struct rcu_head delayed_drop;
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+#endif
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#ifdef CONFIG_HUGETLB_PAGE
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atomic_long_t hugetlb_usage;
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#endif
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--- a/include/linux/sched/mm.h
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+++ b/include/linux/sched/mm.h
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@@ -42,6 +42,17 @@ static inline void mmdrop(struct mm_stru
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__mmdrop(mm);
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}
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+#ifdef CONFIG_PREEMPT_RT_BASE
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+extern void __mmdrop_delayed(struct rcu_head *rhp);
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+static inline void mmdrop_delayed(struct mm_struct *mm)
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+{
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+ if (atomic_dec_and_test(&mm->mm_count))
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+ call_rcu(&mm->delayed_drop, __mmdrop_delayed);
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+}
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+#else
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+# define mmdrop_delayed(mm) mmdrop(mm)
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+#endif
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+
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static inline void mmdrop_async_fn(struct work_struct *work)
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{
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struct mm_struct *mm = container_of(work, struct mm_struct, async_put_work);
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--- a/kernel/fork.c
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+++ b/kernel/fork.c
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@@ -885,6 +885,19 @@ void __mmdrop(struct mm_struct *mm)
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}
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EXPORT_SYMBOL_GPL(__mmdrop);
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+#ifdef CONFIG_PREEMPT_RT_BASE
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+/*
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+ * RCU callback for delayed mm drop. Not strictly rcu, but we don't
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+ * want another facility to make this work.
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+ */
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+void __mmdrop_delayed(struct rcu_head *rhp)
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+{
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+ struct mm_struct *mm = container_of(rhp, struct mm_struct, delayed_drop);
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+
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+ __mmdrop(mm);
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+}
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+#endif
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+
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static inline void __mmput(struct mm_struct *mm)
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{
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VM_BUG_ON(atomic_read(&mm->mm_users));
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--- a/kernel/sched/core.c
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+++ b/kernel/sched/core.c
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@@ -2785,8 +2785,12 @@ static struct rq *finish_task_switch(str
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finish_arch_post_lock_switch();
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fire_sched_in_preempt_notifiers(current);
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+ /*
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+ * We use mmdrop_delayed() here so we don't have to do the
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+ * full __mmdrop() when we are the last user.
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+ */
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if (mm)
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- mmdrop(mm);
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+ mmdrop_delayed(mm);
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if (unlikely(prev_state == TASK_DEAD)) {
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if (prev->sched_class->task_dead)
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prev->sched_class->task_dead(prev);
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@@ -5612,6 +5616,8 @@ void sched_setnuma(struct task_struct *p
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#endif /* CONFIG_NUMA_BALANCING */
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#ifdef CONFIG_HOTPLUG_CPU
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+static DEFINE_PER_CPU(struct mm_struct *, idle_last_mm);
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+
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/*
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* Ensure that the idle task is using init_mm right before its CPU goes
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* offline.
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@@ -5626,7 +5632,12 @@ void idle_task_exit(void)
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switch_mm(mm, &init_mm, current);
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finish_arch_post_lock_switch();
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}
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- mmdrop(mm);
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+ /*
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+ * Defer the cleanup to an alive cpu. On RT we can neither
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+ * call mmdrop() nor mmdrop_delayed() from here.
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+ */
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+ per_cpu(idle_last_mm, smp_processor_id()) = mm;
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+
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}
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/*
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@@ -5953,6 +5964,10 @@ int sched_cpu_dying(unsigned int cpu)
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update_max_interval();
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nohz_balance_exit_idle(cpu);
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hrtick_clear(rq);
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+ if (per_cpu(idle_last_mm, cpu)) {
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+ mmdrop_delayed(per_cpu(idle_last_mm, cpu));
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+ per_cpu(idle_last_mm, cpu) = NULL;
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+ }
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return 0;
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}
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#endif
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