commit ae9a5b85655d7133ab8e7c99b742ef20c8dbb7d2
author Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Mon Jun 26 00:25:26 2006 -0700
committer Linus Torvalds <torvalds@g5.osdl.org> Mon Jun 26 09:58:22 2006 -0700
tree 011bf055ef888a4cfb949fec467bd6385a090d12
parent b71b5b652852db1b499d22aaabed8f5043acafad

[PATCH] Notify page fault call chain for ia64

Overloading of page fault notification with the notify_die() has performance
issues(since the only interested components for page fault is kprobes and/or
kdb) and hence this patch introduces the new notifier call chain exclusively
for page fault notifications their by avoiding notifying unnecessary
components in the do_page_fault() code path.

Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/ia64/mm/fault.c

diff --git a/arch/ia64/mm/fault.c b/arch/ia64/mm/fault.c
index d98ec49..14ef7cc 100644
--- a/arch/ia64/mm/fault.c
+++ b/arch/ia64/mm/fault.c
@@ -19,6 +19,40 @@
 
 extern void die (char *, struct pt_regs *, long);
 
+#ifdef CONFIG_KPROBES
+ATOMIC_NOTIFIER_HEAD(notify_page_fault_chain);
+
+/* Hook to register for page fault notifications */
+int register_page_fault_notifier(struct notifier_block *nb)
+{
+	return atomic_notifier_chain_register(&notify_page_fault_chain, nb);
+}
+
+int unregister_page_fault_notifier(struct notifier_block *nb)
+{
+	return atomic_notifier_chain_unregister(&notify_page_fault_chain, nb);
+}
+
+static inline int notify_page_fault(enum die_val val, const char *str,
+			struct pt_regs *regs, long err, int trap, int sig)
+{
+	struct die_args args = {
+		.regs = regs,
+		.str = str,
+		.err = err,
+		.trapnr = trap,
+		.signr = sig
+	};
+	return atomic_notifier_call_chain(&notify_page_fault_chain, val, &args);
+}
+#else
+static inline int notify_page_fault(enum die_val val, const char *str,
+			struct pt_regs *regs, long err, int trap, int sig)
+{
+	return NOTIFY_DONE;
+}
+#endif
+
 /*
  * Return TRUE if ADDRESS points at a page in the kernel's mapped segment
  * (inside region 5, on ia64) and that page is present.
@@ -84,7 +118,7 @@
 	/*
 	 * This is to handle the kprobes on user space access instructions
 	 */
-	if (notify_die(DIE_PAGE_FAULT, "page fault", regs, code, TRAP_BRKPT,
+	if (notify_page_fault(DIE_PAGE_FAULT, "page fault", regs, code, TRAP_BRKPT,
 					SIGSEGV) == NOTIFY_STOP)
 		return;