Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>

---
 include/linux/kernel.h |    5 +++++
 init/main.c            |    1 +
 kernel/printk.c        |   14 +++++++++++++-
 3 files changed, 19 insertions(+), 1 deletion(-)

Index: linux-2.6/include/linux/kernel.h
===================================================================
--- linux-2.6.orig/include/linux/kernel.h
+++ linux-2.6/include/linux/kernel.h
@@ -190,7 +190,10 @@ extern int kernel_text_address(unsigned
 struct pid;
 extern struct pid *session_of_pgrp(struct pid *pgrp);
 
+typedef unsigned long long (*printk_time_clock_fn)(int cpu);
 #ifdef CONFIG_PRINTK
+extern void set_printk_time_clock(printk_time_clock_fn fn);
+
 asmlinkage int vprintk(const char *fmt, va_list args)
 	__attribute__ ((format (printf, 1, 0)));
 asmlinkage int printk(const char * fmt, ...)
@@ -201,6 +204,8 @@ extern int printk_ratelimit(void);
 extern bool printk_timed_ratelimit(unsigned long *caller_jiffies,
 				   unsigned int interval_msec);
 #else
+static inline void set_printk_time_clock(printk_time_clock_fn fn) { }
+
 static inline int vprintk(const char *s, va_list args)
 	__attribute__ ((format (printf, 1, 0)));
 static inline int vprintk(const char *s, va_list args) { return 0; }
Index: linux-2.6/init/main.c
===================================================================
--- linux-2.6.orig/init/main.c
+++ linux-2.6/init/main.c
@@ -671,6 +671,7 @@ asmlinkage void __init start_kernel(void
 	if (late_time_init)
 		late_time_init();
 	calibrate_delay();
+	set_printk_time_clock(cpu_clock);
 	pidmap_init();
 	pgtable_cache_init();
 	prio_tree_init();
Index: linux-2.6/kernel/printk.c
===================================================================
--- linux-2.6.orig/kernel/printk.c
+++ linux-2.6/kernel/printk.c
@@ -659,6 +659,18 @@ static int recursion_bug;
 	static int new_text_line = 1;
 static char printk_buf[1024];
 
+static unsigned long long default_printk_time_clock(int cpu)
+{
+	return 0;
+}
+
+static ...
[ message continues ]

so can get tsc value on printk at first.

for debug delay with big system with a lot of memory.

need to apply after
	[PATCH] printk_time: prepare stub for using other than cpu_clock

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>

---
 arch/x86/kernel/cpu/common.c    |   11 +++++++++++
 arch/x86/kernel/cpu/common_64.c |   12 ++++++++++++
 2 files changed, 23 insertions(+)

Index: linux-2.6/arch/x86/kernel/cpu/common.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/cpu/common.c
+++ linux-2.6/arch/x86/kernel/cpu/common.c
@@ -647,6 +647,15 @@ __setup("clearcpuid=", setup_disablecpui
 
 cpumask_t cpu_initialized __cpuinitdata = CPU_MASK_NONE;
 
+static unsigned long long tsc_clock(int cpu)
+{
+	unsigned long long t;
+
+	rdtscll(t);
+
+	return t;
+}
+
 void __init early_cpu_init(void)
 {
 	struct cpu_vendor_dev *cvdev;
@@ -657,6 +666,8 @@ void __init early_cpu_init(void)
 		cpu_devs[cvdev->vendor] = cvdev->cpu_dev;
 
 	early_cpu_detect();
+	if (cpu_has_tsc)
+		set_printk_time_clock(tsc_clock);
 	validate_pat_support(&boot_cpu_data);
 }
 
Index: linux-2.6/arch/x86/kernel/cpu/common_64.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/cpu/common_64.c
+++ linux-2.6/arch/x86/kernel/cpu/common_64.c
@@ -249,6 +249,15 @@ static void __cpuinit detect_nopl(struct
 	}
 }
 
+static unsigned long long tsc_clock(int cpu)
+{
+	unsigned long long t;
+
+	rdtscll(t);
+
+	return t;
+}
+
 static void __cpuinit early_identify_cpu(struct cpuinfo_x86 *c);
 
 void __init early_cpu_init(void)
@@ -261,6 +270,9 @@ void __init early_cpu_init(void)
                 cpu_devs[cvdev->vendor] = cvdev->cpu_dev;
 	early_cpu_support_print();
 	early_identify_cpu(&boot_cpu_data);
+
+	if (cpu_has_tsc)
+		set_printk_time_clock(tsc_clock);
 }
 
 /* Do some early cpuid on the boot CPU to get some parameter that are
--

[ message continues ]

hm, i'm not sure i like the whole direction - this reintroduces 
printk_clock in essence.

how about initializing cpu_clock() sooner, so that printk timestamps 
start ticking as soon as possible?

	Ingo
--

[ message continues ]

which will make some archs quite unhappy iirc, see those arm and ia64
bugs I caused the other day.

--

[ message continues ]

that's OK - that still allows arches to start their clocks whenever they 
want to. But also add the possibility for architectures to initialize 
things even sooner.

	Ingo
--

[ message continues ]