100 lines
3.0 KiB
Diff
100 lines
3.0 KiB
Diff
From 3691a6aac0ee8777a3ebd30b1dcfbfc3b254af9b Mon Sep 17 00:00:00 2001
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Message-Id: <3691a6aac0ee8777a3ebd30b1dcfbfc3b254af9b.1592846147.git.zanussi@kernel.org>
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In-Reply-To: <07cd0dbc80b976663c80755496a03f288decfe5a.1592846146.git.zanussi@kernel.org>
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References: <07cd0dbc80b976663c80755496a03f288decfe5a.1592846146.git.zanussi@kernel.org>
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From: Thomas Gleixner <tglx@linutronix.de>
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Date: Mon, 6 Jun 2011 12:20:33 +0200
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Subject: [PATCH 107/330] sched: Move mmdrop to RCU on RT
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.127-rt55.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 | 18 ++++++++++++++++--
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4 files changed, 44 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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@@ -12,6 +12,7 @@
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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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@@ -489,6 +490,9 @@ struct mm_struct {
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bool tlb_flush_batched;
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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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@@ -51,6 +51,17 @@ static inline void mmdrop(struct mm_stru
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void mmdrop(struct mm_struct *mm);
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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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/*
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* This has to be called after a get_task_mm()/mmget_not_zero()
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* followed by taking the mmap_sem for writing before modifying the
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--- a/kernel/fork.c
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+++ b/kernel/fork.c
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@@ -647,6 +647,19 @@ 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 void mmdrop_async_fn(struct work_struct *work)
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{
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struct mm_struct *mm;
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--- a/kernel/sched/core.c
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+++ b/kernel/sched/core.c
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@@ -2729,9 +2729,13 @@ static struct rq *finish_task_switch(str
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* provided by mmdrop(),
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* - a sync_core for SYNC_CORE.
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*/
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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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membarrier_mm_sync_core_before_usermode(mm);
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- mmdrop(mm);
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+ mmdrop_delayed(mm);
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}
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if (unlikely(prev_state == TASK_DEAD)) {
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if (prev->sched_class->task_dead)
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