From: Anil S Keshavamurthy 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 Signed-off-by: Andrew Morton --- arch/ia64/mm/fault.c | 36 +++++++++++++++++++++++++++++++++++- include/asm-ia64/kdebug.h | 2 ++ 2 files changed, 37 insertions(+), 1 deletion(-) diff -puN arch/ia64/mm/fault.c~notify-page-fault-call-chain-for-ia64 arch/ia64/mm/fault.c --- devel/arch/ia64/mm/fault.c~notify-page-fault-call-chain-for-ia64 2006-06-09 15:18:09.000000000 -0700 +++ devel-akpm/arch/ia64/mm/fault.c 2006-06-09 15:18:09.000000000 -0700 @@ -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(¬ify_page_fault_chain, nb); +} + +int unregister_page_fault_notifier(struct notifier_block *nb) +{ + return atomic_notifier_chain_unregister(¬ify_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(¬ify_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 @@ ia64_do_page_fault (unsigned long addres /* * 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; diff -puN include/asm-ia64/kdebug.h~notify-page-fault-call-chain-for-ia64 include/asm-ia64/kdebug.h --- devel/include/asm-ia64/kdebug.h~notify-page-fault-call-chain-for-ia64 2006-06-09 15:18:09.000000000 -0700 +++ devel-akpm/include/asm-ia64/kdebug.h 2006-06-09 15:18:09.000000000 -0700 @@ -40,6 +40,8 @@ struct die_args { extern int register_die_notifier(struct notifier_block *); extern int unregister_die_notifier(struct notifier_block *); +extern int register_page_fault_notifier(struct notifier_block *); +extern int unregister_page_fault_notifier(struct notifier_block *); extern struct atomic_notifier_head ia64die_chain; enum die_val { _