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From 057de3e45b5e87c9f4bf0d75b055999a65a85ea9 Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@elte.hu>
Date: Fri, 3 Jul 2009 08:30:37 -0500
Subject: [PATCH] mm: Prepare decoupling the page fault disabling logic
commit 5e918aee03250bd6416175794d4673ff4b9ed583 in tip.
Add a pagefault_disabled variable to task_struct to allow decoupling
the pagefault-disabled logic from the preempt count.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
include/linux/sched.h | 1 +
include/linux/uaccess.h | 33 +++------------------------------
kernel/fork.c | 1 +
mm/memory.c | 29 +++++++++++++++++++++++++++++
4 files changed, 34 insertions(+), 30 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 53e6ffe..bdcdabd 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1224,6 +1224,7 @@ struct task_struct {
struct plist_node pushable_tasks;
struct mm_struct *mm, *active_mm;
+ int pagefault_disabled;
#if defined(SPLIT_RSS_COUNTING)
struct task_rss_stat rss_stat;
#endif
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index d512d98..9c7e38a 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -6,37 +6,10 @@
/*
* These routines enable/disable the pagefault handler in that
- * it will not take any locks and go straight to the fixup table.
- *
- * They have great resemblance to the preempt_disable/enable calls
- * and in fact they are identical; this is because currently there is
- * no other way to make the pagefault handlers do this. So we do
- * disable preemption but we don't necessarily care about that.
+ * it will not take any MM locks and go straight to the fixup table.
*/
-static inline void pagefault_disable(void)
-{
- inc_preempt_count();
- /*
- * make sure to have issued the store before a pagefault
- * can hit.
- */
- barrier();
-}
-
-static inline void pagefault_enable(void)
-{
- /*
- * make sure to issue those last loads/stores before enabling
- * the pagefault handler again.
- */
- barrier();
- dec_preempt_count();
- /*
- * make sure we do..
- */
- barrier();
- preempt_check_resched();
-}
+extern void pagefault_disable(void);
+extern void pagefault_enable(void);
#ifndef ARCH_HAS_NOCACHE_UACCESS
diff --git a/kernel/fork.c b/kernel/fork.c
index 4c14942..0a1b8d1 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1098,6 +1098,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
p->hardirq_context = 0;
p->softirq_context = 0;
#endif
+ p->pagefault_disabled = 0;
#ifdef CONFIG_LOCKDEP
p->lockdep_depth = 0; /* no locks held yet */
p->curr_chain_key = 0;
diff --git a/mm/memory.c b/mm/memory.c
index 90f674e..17056a3 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3107,6 +3107,35 @@ unlock:
return 0;
}
+void pagefault_disable(void)
+{
+ inc_preempt_count();
+ current->pagefault_disabled++;
+ /*
+ * make sure to have issued the store before a pagefault
+ * can hit.
+ */
+ barrier();
+}
+EXPORT_SYMBOL(pagefault_disable);
+
+void pagefault_enable(void)
+{
+ /*
+ * make sure to issue those last loads/stores before enabling
+ * the pagefault handler again.
+ */
+ barrier();
+ current->pagefault_disabled--;
+ dec_preempt_count();
+ /*
+ * make sure we do..
+ */
+ barrier();
+ preempt_check_resched();
+}
+EXPORT_SYMBOL(pagefault_enable);
+
/*
* By the time we get here, we already hold the mm semaphore
*/
--
1.7.0.4
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