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Date: Thu, 3 Jan 2008 12:52:10 -0500
From: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Christoph Hellwig <hch@...radead.org>,
Gregory Haskins <ghaskins@...ell.com>,
Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
"William L. Irwin" <sparclinux@...r.kernel.org>,
Steven Rostedt <srostedt@...hat.com>
Subject: Re: [RFC PATCH 04/11] i386: notrace annotations
* Steven Rostedt (rostedt@...dmis.org) wrote:
> From patch-2.6.21.5-rt20. Annotates functions that should not be profiler
> instrumented, i.e. where mcount should not be called at function entry.
>
> Signed-off-by: Arnaldo Carvalho de Melo <acme@...stprotocols.net>
> Signed-off-by: Steven Rostedt <srostedt@...hat.com>
> ---
> arch/x86/kernel/apic_32.c | 2 +-
> arch/x86/kernel/hpet.c | 2 +-
> arch/x86/kernel/irq_32.c | 2 +-
> arch/x86/kernel/nmi_32.c | 2 +-
> arch/x86/kernel/smp_32.c | 2 +-
> arch/x86/kernel/time_32.c | 2 +-
> arch/x86/kernel/traps_32.c | 4 ++--
> arch/x86/kernel/tsc_32.c | 2 +-
> arch/x86/lib/delay_32.c | 6 +++---
> arch/x86/mm/fault_32.c | 4 ++--
> arch/x86/mm/init_32.c | 2 +-
> 11 files changed, 15 insertions(+), 15 deletions(-)
> ---
>
> Index: linux-compile.git/arch/x86/kernel/apic_32.c
> ===================================================================
> --- linux-compile.git.orig/arch/x86/kernel/apic_32.c 2008-01-02 22:53:52.000000000 -0500
> +++ linux-compile.git/arch/x86/kernel/apic_32.c 2008-01-02 22:56:41.000000000 -0500
> @@ -577,7 +577,7 @@ static void local_apic_timer_interrupt(v
> * interrupt as well. Thus we cannot inline the local irq ... ]
> */
>
> -void fastcall smp_apic_timer_interrupt(struct pt_regs *regs)
> +notrace fastcall void smp_apic_timer_interrupt(struct pt_regs *regs)
> {
> struct pt_regs *old_regs = set_irq_regs(regs);
>
Why can't this be traced ?
> Index: linux-compile.git/arch/x86/kernel/hpet.c
> ===================================================================
> --- linux-compile.git.orig/arch/x86/kernel/hpet.c 2008-01-02 22:53:52.000000000 -0500
> +++ linux-compile.git/arch/x86/kernel/hpet.c 2008-01-02 22:56:41.000000000 -0500
> @@ -295,7 +295,7 @@ static int hpet_legacy_next_event(unsign
> /*
> * Clock source related code
> */
> -static cycle_t read_hpet(void)
> +static notrace cycle_t read_hpet(void)
> {
> return (cycle_t)hpet_readl(HPET_COUNTER);
> }
This one is weird on x86 32 : a 32 bits value is casted into a
(cycles_t), which is an unsigned long long. So we think we have a 64
bits counter when in fact we only have 32 bits. How long before the wrap
around ?
> Index: linux-compile.git/arch/x86/kernel/irq_32.c
> ===================================================================
> --- linux-compile.git.orig/arch/x86/kernel/irq_32.c 2008-01-02 22:56:34.000000000 -0500
> +++ linux-compile.git/arch/x86/kernel/irq_32.c 2008-01-02 22:56:41.000000000 -0500
> @@ -66,7 +66,7 @@ static union irq_ctx *softirq_ctx[NR_CPU
> * SMP cross-CPU interrupts have their own specific
> * handlers).
> */
> -fastcall unsigned int do_IRQ(struct pt_regs *regs)
> +notrace fastcall unsigned int do_IRQ(struct pt_regs *regs)
Why ?
> {
> struct pt_regs *old_regs;
> /* high bit used in ret_from_ code */
> Index: linux-compile.git/arch/x86/kernel/nmi_32.c
> ===================================================================
> --- linux-compile.git.orig/arch/x86/kernel/nmi_32.c 2008-01-02 22:53:52.000000000 -0500
> +++ linux-compile.git/arch/x86/kernel/nmi_32.c 2008-01-02 22:57:52.000000000 -0500
> @@ -323,7 +323,7 @@ EXPORT_SYMBOL(touch_nmi_watchdog);
>
> extern void die_nmi(struct pt_regs *, const char *msg);
>
> -__kprobes int nmi_watchdog_tick(struct pt_regs * regs, unsigned reason)
> +notrace __kprobes int nmi_watchdog_tick(struct pt_regs *regs, unsigned reason)
> {
Why ? ... hrm, this is dangerous : you will then have to look at _every_
code path that can be run in an NMI context (printk included) and mark
them "notrace" or make sure your tracer is disabled when they are run.
>
> /*
> Index: linux-compile.git/arch/x86/kernel/smp_32.c
> ===================================================================
> --- linux-compile.git.orig/arch/x86/kernel/smp_32.c 2008-01-02 22:53:52.000000000 -0500
> +++ linux-compile.git/arch/x86/kernel/smp_32.c 2008-01-02 22:56:41.000000000 -0500
> @@ -638,7 +638,7 @@ static void native_smp_send_stop(void)
> * all the work is done automatically when
> * we return from the interrupt.
> */
> -fastcall void smp_reschedule_interrupt(struct pt_regs *regs)
> +notrace fastcall void smp_reschedule_interrupt(struct pt_regs *regs)
why?
> {
> ack_APIC_irq();
> __get_cpu_var(irq_stat).irq_resched_count++;
> Index: linux-compile.git/arch/x86/kernel/time_32.c
> ===================================================================
> --- linux-compile.git.orig/arch/x86/kernel/time_32.c 2008-01-02 22:53:52.000000000 -0500
> +++ linux-compile.git/arch/x86/kernel/time_32.c 2008-01-02 22:56:41.000000000 -0500
> @@ -122,7 +122,7 @@ static int set_rtc_mmss(unsigned long no
>
> int timer_ack;
>
> -unsigned long profile_pc(struct pt_regs *regs)
> +notrace unsigned long profile_pc(struct pt_regs *regs)
> {
> unsigned long pc = instruction_pointer(regs);
>
> Index: linux-compile.git/arch/x86/kernel/traps_32.c
> ===================================================================
> --- linux-compile.git.orig/arch/x86/kernel/traps_32.c 2008-01-02 22:53:52.000000000 -0500
> +++ linux-compile.git/arch/x86/kernel/traps_32.c 2008-01-02 22:58:19.000000000 -0500
> @@ -723,7 +723,7 @@ void __kprobes die_nmi(struct pt_regs *r
> do_exit(SIGSEGV);
> }
>
> -static __kprobes void default_do_nmi(struct pt_regs * regs)
> +static notrace __kprobes void default_do_nmi(struct pt_regs *regs)
> {
> unsigned char reason = 0;
>
> @@ -763,7 +763,7 @@ static __kprobes void default_do_nmi(str
>
> static int ignore_nmis;
>
> -fastcall __kprobes void do_nmi(struct pt_regs * regs, long error_code)
> +notrace fastcall __kprobes void do_nmi(struct pt_regs *regs, long error_code)
> {
> int cpu;
>
Same here.. we must be careful, or use atomic ops instead of interrupt
disabling.
> Index: linux-compile.git/arch/x86/kernel/tsc_32.c
> ===================================================================
> --- linux-compile.git.orig/arch/x86/kernel/tsc_32.c 2008-01-02 22:53:52.000000000 -0500
> +++ linux-compile.git/arch/x86/kernel/tsc_32.c 2008-01-02 22:56:41.000000000 -0500
> @@ -269,7 +269,7 @@ core_initcall(cpufreq_tsc);
>
> static unsigned long current_tsc_khz = 0;
>
> -static cycle_t read_tsc(void)
> +static notrace cycle_t read_tsc(void)
> {
> cycle_t ret;
>
> Index: linux-compile.git/arch/x86/lib/delay_32.c
> ===================================================================
> --- linux-compile.git.orig/arch/x86/lib/delay_32.c 2008-01-02 22:53:52.000000000 -0500
> +++ linux-compile.git/arch/x86/lib/delay_32.c 2008-01-02 22:56:41.000000000 -0500
> @@ -24,7 +24,7 @@
> #endif
>
> /* simple loop based delay: */
> -static void delay_loop(unsigned long loops)
> +static notrace void delay_loop(unsigned long loops)
> {
> int d0;
>
> @@ -39,7 +39,7 @@ static void delay_loop(unsigned long loo
> }
>
> /* TSC based delay: */
> -static void delay_tsc(unsigned long loops)
> +static notrace void delay_tsc(unsigned long loops)
> {
> unsigned long bclock, now;
>
> @@ -72,7 +72,7 @@ int read_current_timer(unsigned long *ti
> return -1;
> }
>
> -void __delay(unsigned long loops)
> +notrace void __delay(unsigned long loops)
> {
> delay_fn(loops);
> }
> Index: linux-compile.git/arch/x86/mm/fault_32.c
> ===================================================================
> --- linux-compile.git.orig/arch/x86/mm/fault_32.c 2008-01-02 22:53:52.000000000 -0500
> +++ linux-compile.git/arch/x86/mm/fault_32.c 2008-01-02 22:56:41.000000000 -0500
> @@ -293,8 +293,8 @@ int show_unhandled_signals = 1;
> * bit 3 == 1 means use of reserved bit detected
> * bit 4 == 1 means fault was an instruction fetch
> */
> -fastcall void __kprobes do_page_fault(struct pt_regs *regs,
> - unsigned long error_code)
> +notrace fastcall void __kprobes do_page_fault(struct pt_regs *regs,
> + unsigned long error_code)
Agreed on this one. It get's called when new modules are loaded for
in-kernel faults. Hard to trace. Will vmalloc_fault, an inline function,
trigger an mcount call ?
> {
> struct task_struct *tsk;
> struct mm_struct *mm;
> Index: linux-compile.git/arch/x86/mm/init_32.c
> ===================================================================
> --- linux-compile.git.orig/arch/x86/mm/init_32.c 2008-01-02 22:53:52.000000000 -0500
> +++ linux-compile.git/arch/x86/mm/init_32.c 2008-01-02 22:56:41.000000000 -0500
> @@ -200,7 +200,7 @@ static inline int page_kills_ppro(unsign
> return 0;
> }
>
> -int page_is_ram(unsigned long pagenr)
> +notrace int page_is_ram(unsigned long pagenr)
> {
> int i;
> unsigned long addr, end;
>
> --
--
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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