[patch 03/52] [PATCH] Improve notify_page_fault implementation.

[Martin Schwidefsky]

From: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>

notify_page_fault does a preempt_disable/preempt_enable for each
fault generated by a kernel access to user space. If kprobes
is not active that is unnecessary since the interrupts are not
reenabled yet. To play safe repeat the kprobe_running check after
preempt_disable().

Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
---

 arch/s390/mm/fault.c |   14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

Index: quilt-2.6/arch/s390/mm/fault.c
===================================================================
--- quilt-2.6.orig/arch/s390/mm/fault.c	2009-11-13 16:08:12.000000000 +0100
+++ quilt-2.6/arch/s390/mm/fault.c	2009-11-13 16:08:12.000000000 +0100
@@ -52,11 +52,11 @@
 extern int sysctl_userprocess_debug;
 #endif
 
-#ifdef CONFIG_KPROBES
-static inline int notify_page_fault(struct pt_regs *regs, long err)
+static inline int notify_page_fault(struct pt_regs *regs)
 {
 	int ret = 0;
 
+#ifdef CONFIG_KPROBES
 	/* kprobe_running() needs smp_processor_id() */
 	if (!user_mode(regs)) {
 		preempt_disable();
@@ -64,15 +64,9 @@
 			ret = 1;
 		preempt_enable();
 	}
-
+#endif
 	return ret;
 }
-#else
-static inline int notify_page_fault(struct pt_regs *regs, long err)
-{
-	return 0;
-}
-#endif
 
 
 /*
@@ -274,7 +268,7 @@
 	int si_code;
 	int fault;
 
-	if (notify_page_fault(regs, error_code))
+	if (notify_page_fault(regs))
 		return;
 
 	tsk = current;

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