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Subject[patch 08/17] Trace clock generic
Wrapper to use the lower level clock sources available on the systems. Fall-back
on a counter incremented by a timer interrupt every jiffy or'd with a logical
clock for architectures lacking CPU timestamp counters.

A generic fallback based on a logical clock and the timer interrupt is
available.

generic - Uses jiffies or'd with a logical clock extended to 64 bits by
trace-clock-32-to-64.
i386 - Uses TSC. If detects non synchronized TSC, uses mixed TSC-logical clock.
mips - Uses TSC extended atomically from 32 to 64 bits by trace-clock-32-to-64.
powerpc - Uses TSC.
sparc64 - Uses TSC.
x86_64 - Uses TSC. If detects non synchronized TSC, uses mixed TSC-logical clock

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
CC: Ralf Baechle <ralf@linux-mips.org>
CC: benh@kernel.crashing.org
CC: paulus@samba.org
CC: David Miller <davem@davemloft.net>
CC: Linus Torvalds <torvalds@linux-foundation.org>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Ingo Molnar <mingo@redhat.com>
CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Steven Rostedt <rostedt@goodmis.org>
CC: linux-arch@vger.kernel.org
---
include/asm-generic/trace-clock.h | 64 +++++++++++++++++++++++++
include/linux/trace-clock.h | 17 ++++++
init/Kconfig | 6 ++
kernel/trace/Makefile | 1
kernel/trace/trace-clock.c | 97 ++++++++++++++++++++++++++++++++++++++
5 files changed, 185 insertions(+)
Index: linux.trees.git/include/asm-generic/trace-clock.h
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux.trees.git/include/asm-generic/trace-clock.h 2008-11-26 06:51:47.000000000 -0500
@@ -0,0 +1,64 @@
+#ifndef _ASM_GENERIC_TRACE_CLOCK_H
+#define _ASM_GENERIC_TRACE_CLOCK_H
+
+/*
+ * include/asm-generic/trace-clock.h
+ *
+ * Copyright (C) 2007 - Mathieu Desnoyers (mathieu.desnoyers@polymtl.ca)
+ *
+ * Generic tracing clock for architectures without TSC.
+ */
+
+#include <linux/param.h> /* For HZ */
+#include <asm/atomic.h>
+
+#define TRACE_CLOCK_SHIFT 13
+
+extern atomic_long_t trace_clock;
+
+static inline u32 trace_clock_read32(void)
+{
+ return (u32)atomic_long_add_return(1, &trace_clock);
+}
+
+#ifdef CONFIG_HAVE_TRACE_CLOCK_32_TO_64
+extern u64 trace_clock_read_synthetic_tsc(void);
+extern void get_synthetic_tsc(void);
+extern void put_synthetic_tsc(void);
+
+static inline u64 trace_clock_read64(void)
+{
+ return trace_clock_read_synthetic_tsc();
+}
+#else
+static inline void get_synthetic_tsc(void)
+{
+}
+
+static inline void put_synthetic_tsc(void)
+{
+}
+
+static inline u64 trace_clock_read64(void)
+{
+ return atomic_long_add_return(1, &trace_clock);
+}
+#endif
+
+static inline unsigned int trace_clock_frequency(void)
+{
+ return HZ << TRACE_CLOCK_SHIFT;
+}
+
+static inline u32 trace_clock_freq_scale(void)
+{
+ return 1;
+}
+
+extern void get_trace_clock(void);
+extern void put_trace_clock(void);
+
+static inline void set_trace_clock_is_sync(int state)
+{
+}
+#endif /* _ASM_GENERIC_TRACE_CLOCK_H */
Index: linux.trees.git/include/linux/trace-clock.h
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux.trees.git/include/linux/trace-clock.h 2008-11-26 06:51:47.000000000 -0500
@@ -0,0 +1,17 @@
+#ifndef _LINUX_TRACE_CLOCK_H
+#define _LINUX_TRACE_CLOCK_H
+
+/*
+ * Trace clock
+ *
+ * Chooses between an architecture specific clock or an atomic logical clock.
+ *
+ * Copyright (C) 2007,2008 Mathieu Desnoyers (mathieu.desnoyers@polymtl.ca)
+ */
+
+#ifdef CONFIG_HAVE_TRACE_CLOCK
+#include <asm/trace-clock.h>
+#else
+#include <asm-generic/trace-clock.h>
+#endif /* CONFIG_HAVE_TRACE_CLOCK */
+#endif /* _LINUX_TRACE_CLOCK_H */
Index: linux.trees.git/kernel/trace/trace-clock.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux.trees.git/kernel/trace/trace-clock.c 2008-11-26 06:51:47.000000000 -0500
@@ -0,0 +1,97 @@
+/*
+ * kernel/trace/trace-clock.c
+ *
+ * (C) Copyright 2008 -
+ * Mathieu Desnoyers (mathieu.desnoyers@polymtl.ca)
+ *
+ * Generic kernel tracing clock for architectures without TSC.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/delay.h>
+#include <linux/timer.h>
+#include <linux/workqueue.h>
+#include <linux/cpu.h>
+#include <linux/timex.h>
+#include <linux/bitops.h>
+#include <linux/trace-clock.h>
+#include <linux/jiffies.h>
+
+static int trace_clock_refcount;
+static DEFINE_MUTEX(trace_clock_mutex);
+static struct timer_list trace_clock_timer;
+/*
+ * bits 0..12 : counter, atomically incremented
+ * bits 13..{32,64} : time counter, incremented each jiffy.
+ */
+atomic_long_t trace_clock;
+EXPORT_SYMBOL(trace_clock);
+
+static void trace_clock_update(void)
+{
+ long old_clock, new_clock;
+ unsigned long ticks;
+
+ /*
+ * Make sure we keep track of delayed timer.
+ */
+ ticks = jiffies - trace_clock_timer.expires + 1;
+ /* Don't update if ticks is zero, time would go backward. */
+ if (unlikely(!ticks))
+ return;
+ do {
+ old_clock = atomic_long_read(&trace_clock);
+ new_clock = (old_clock + (ticks << TRACE_CLOCK_SHIFT))
+ & (~((1 << TRACE_CLOCK_SHIFT) - 1));
+ } while (atomic_long_cmpxchg(&trace_clock, old_clock, new_clock)
+ != old_clock);
+}
+
+static void trace_clock_timer_fct(unsigned long data)
+{
+ trace_clock_update();
+ trace_clock_timer.expires = jiffies + 1;
+ add_timer(&trace_clock_timer);
+}
+
+static void enable_trace_clock(void)
+{
+ init_timer(&trace_clock_timer);
+ /* trace_clock_update() reads expires */
+ trace_clock_timer.function = trace_clock_timer_fct;
+ trace_clock_timer.expires = jiffies + 1;
+ trace_clock_update();
+ add_timer(&trace_clock_timer);
+}
+
+static void disable_trace_clock(void)
+{
+ del_timer_sync(&trace_clock_timer);
+}
+
+void get_trace_clock(void)
+{
+ get_synthetic_tsc();
+ mutex_lock(&trace_clock_mutex);
+ if (trace_clock_refcount++)
+ goto end;
+ enable_trace_clock();
+end:
+ mutex_unlock(&trace_clock_mutex);
+}
+EXPORT_SYMBOL_GPL(get_trace_clock);
+
+void put_trace_clock(void)
+{
+ mutex_lock(&trace_clock_mutex);
+ WARN_ON(trace_clock_refcount <= 0);
+ if (trace_clock_refcount != 1)
+ goto end;
+ disable_trace_clock();
+end:
+ trace_clock_refcount--;
+ mutex_unlock(&trace_clock_mutex);
+ put_synthetic_tsc();
+}
+EXPORT_SYMBOL_GPL(put_trace_clock);
Index: linux.trees.git/init/Kconfig
===================================================================
--- linux.trees.git.orig/init/Kconfig 2008-11-26 06:49:43.000000000 -0500
+++ linux.trees.git/init/Kconfig 2008-11-26 06:51:47.000000000 -0500
@@ -346,6 +346,12 @@ config HAVE_GET_CYCLES
config HAVE_TRACE_CLOCK
def_bool n

+config HAVE_TRACE_CLOCK_GENERIC
+ bool
+ default y if (!HAVE_TRACE_CLOCK)
+ default n if HAVE_TRACE_CLOCK
+ select HAVE_TRACE_CLOCK_32_TO_64 if (!64BIT)
+
#
# Architectures with only a 32-bits clock source should select this.
#
Index: linux.trees.git/kernel/trace/Makefile
===================================================================
--- linux.trees.git.orig/kernel/trace/Makefile 2008-11-26 06:50:07.000000000 -0500
+++ linux.trees.git/kernel/trace/Makefile 2008-11-26 06:51:47.000000000 -0500
@@ -34,5 +34,6 @@ obj-$(CONFIG_TRACE_BRANCH_PROFILING) +=
obj-$(CONFIG_BTS_TRACER) += trace_bts.o
obj-$(CONFIG_POWER_TRACER) += trace_power.o
obj-$(CONFIG_HAVE_TRACE_CLOCK_32_TO_64) += trace-clock-32-to-64.o
+obj-$(CONFIG_HAVE_TRACE_CLOCK_GENERIC) += trace-clock.o

libftrace-y := ftrace.o
--
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68


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