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/i386/mm/fault.c | 38 ++++++++++++++++++++++++++++++++++-- include/asm-i386/kdebug.h | 2 + 2 files changed, 38 insertions(+), 2 deletions(-) diff -puN arch/i386/mm/fault.c~notify-page-fault-call-chain-for-i386 arch/i386/mm/fault.c --- devel/arch/i386/mm/fault.c~notify-page-fault-call-chain-for-i386 2006-04-20 23:29:59.000000000 -0700 +++ devel-akpm/arch/i386/mm/fault.c 2006-04-20 23:29:59.000000000 -0700 @@ -30,6 +30,40 @@ extern void die(const char *,struct pt_regs *,long); +#ifdef CONFIG_KPROBES +ATOMIC_NOTIFIER_HEAD(notify_page_fault_chain); +int register_page_fault_notifier(struct notifier_block *nb) +{ + vmalloc_sync_all(); + 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 + + /* * Unlock any spinlocks which will prevent us from getting the * message out @@ -321,7 +355,7 @@ fastcall void __kprobes do_page_fault(st if (unlikely(address >= TASK_SIZE)) { if (!(error_code & 0x0000000d) && vmalloc_fault(address) >= 0) return; - if (notify_die(DIE_PAGE_FAULT, "page fault", regs, error_code, 14, + if (notify_page_fault(DIE_PAGE_FAULT, "page fault", regs, error_code, 14, SIGSEGV) == NOTIFY_STOP) return; /* @@ -331,7 +365,7 @@ fastcall void __kprobes do_page_fault(st goto bad_area_nosemaphore; } - if (notify_die(DIE_PAGE_FAULT, "page fault", regs, error_code, 14, + if (notify_page_fault(DIE_PAGE_FAULT, "page fault", regs, error_code, 14, SIGSEGV) == NOTIFY_STOP) return; diff -puN include/asm-i386/kdebug.h~notify-page-fault-call-chain-for-i386 include/asm-i386/kdebug.h --- devel/include/asm-i386/kdebug.h~notify-page-fault-call-chain-for-i386 2006-04-20 23:29:59.000000000 -0700 +++ devel-akpm/include/asm-i386/kdebug.h 2006-04-20 23:29:59.000000000 -0700 @@ -19,6 +19,8 @@ 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 i386die_chain; _