lttng-instrumentation/revert-marker-remove

revert marker remove

LTTng tree (internal).

revert commit fc5377668c3d808e1d53c4aee152c836f55c3490

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>

17 files changed, 1464 insertions, 1 deletions

diff --git a/Documentation/markers.txt b/Documentation/markers.txt
new file mode 100644
index 00000000000..d2b3d0e91b2
--- /dev/null
+++ b/Documentation/markers.txt
@@ -0,0 +1,104 @@
+ 	             Using the Linux Kernel Markers
+
+			    Mathieu Desnoyers
+
+
+This document introduces Linux Kernel Markers and their use. It provides
+examples of how to insert markers in the kernel and connect probe functions to
+them and provides some examples of probe functions.
+
+
+* Purpose of markers
+
+A marker placed in code provides a hook to call a function (probe) that you can
+provide at runtime. A marker can be "on" (a probe is connected to it) or "off"
+(no probe is attached). When a marker is "off" it has no effect, except for
+adding a tiny time penalty (checking a condition for a branch) and space
+penalty (adding a few bytes for the function call at the end of the
+instrumented function and adds a data structure in a separate section).  When a
+marker is "on", the function you provide is called each time the marker is
+executed, in the execution context of the caller. When the function provided
+ends its execution, it returns to the caller (continuing from the marker site).
+
+You can put markers at important locations in the code. Markers are
+lightweight hooks that can pass an arbitrary number of parameters,
+described in a printk-like format string, to the attached probe function.
+
+They can be used for tracing and performance accounting.
+
+
+* Usage
+
+In order to use the macro trace_mark, you should include linux/marker.h.
+
+#include <linux/marker.h>
+
+And,
+
+trace_mark(subsystem_event, "myint %d mystring %s", someint, somestring);
+Where :
+- subsystem_event is an identifier unique to your event
+    - subsystem is the name of your subsystem.
+    - event is the name of the event to mark.
+- "myint %d mystring %s" is the formatted string for the serializer. "myint" and
+  "mystring" are repectively the field names associated with the first and
+  second parameter.
+- someint is an integer.
+- somestring is a char pointer.
+
+Connecting a function (probe) to a marker is done by providing a probe (function
+to call) for the specific marker through marker_probe_register() and can be
+activated by calling marker_arm(). Marker deactivation can be done by calling
+marker_disarm() as many times as marker_arm() has been called. Removing a probe
+is done through marker_probe_unregister(); it will disarm the probe.
+
+marker_synchronize_unregister() must be called between probe unregistration and
+the first occurrence of
+- the end of module exit function,
+  to make sure there is no caller left using the probe;
+- the free of any resource used by the probes,
+  to make sure the probes wont be accessing invalid data.
+This, and the fact that preemption is disabled around the probe call, make sure
+that probe removal and module unload are safe. See the "Probe example" section
+below for a sample probe module.
+
+The marker mechanism supports inserting multiple instances of the same marker.
+Markers can be put in inline functions, inlined static functions, and
+unrolled loops as well as regular functions.
+
+The naming scheme "subsystem_event" is suggested here as a convention intended
+to limit collisions. Marker names are global to the kernel: they are considered
+as being the same whether they are in the core kernel image or in modules.
+Conflicting format strings for markers with the same name will cause the markers
+to be detected to have a different format string not to be armed and will output
+a printk warning which identifies the inconsistency:
+
+"Format mismatch for probe probe_name (format), marker (format)"
+
+Another way to use markers is to simply define the marker without generating any
+function call to actually call into the marker. This is useful in combination
+with tracepoint probes in a scheme like this :
+
+void probe_tracepoint_name(unsigned int arg1, struct task_struct *tsk);
+
+DEFINE_MARKER_TP(marker_eventname, tracepoint_name, probe_tracepoint_name,
+	"arg1 %u pid %d");
+
+notrace void probe_tracepoint_name(unsigned int arg1, struct task_struct *tsk)
+{
+	struct marker *marker = &GET_MARKER(kernel_irq_entry);
+	/* write data to trace buffers ... */
+}
+
+* Probe / marker example
+
+See the example provided in samples/markers/src
+
+Compile them with your kernel.
+
+Run, as root :
+modprobe marker-example (insmod order is not important)
+modprobe probe-example
+cat /proc/marker-example (returns an expected error)
+rmmod marker-example probe-example
+dmesg
diff --git a/arch/powerpc/platforms/cell/spufs/file.c b/arch/powerpc/platforms/cell/spufs/file.c
index 3c7c3f82d84..3f098525259 100644
--- a/arch/powerpc/platforms/cell/spufs/file.c
+++ b/arch/powerpc/platforms/cell/spufs/file.c
@@ -30,6 +30,7 @@
 #include <linux/ptrace.h>
 #include <linux/seq_file.h>
 #include <linux/slab.h>
+#include <linux/marker.h>
 
 #include <asm/io.h>
 #include <asm/time.h>
diff --git a/arch/powerpc/platforms/cell/spufs/sched.c b/arch/powerpc/platforms/cell/spufs/sched.c
index 0b046628493..a7b4b883863 100644
--- a/arch/powerpc/platforms/cell/spufs/sched.c
+++ b/arch/powerpc/platforms/cell/spufs/sched.c
@@ -40,6 +40,7 @@
 #include <linux/pid_namespace.h>
 #include <linux/proc_fs.h>
 #include <linux/seq_file.h>
+#include <linux/marker.h>
 
 #include <asm/io.h>
 #include <asm/mmu_context.h>
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index b5021db2185..914f0196130 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -15,6 +15,7 @@
 #include <linux/sched.h>
 #include <linux/mm.h>
 #include <linux/preempt.h>
+#include <linux/marker.h>
 #include <linux/msi.h>
 #include <linux/slab.h>
 #include <linux/rcupdate.h>
diff --git a/include/linux/marker.h b/include/linux/marker.h
new file mode 100644
index 00000000000..b85e74ca782
--- /dev/null
+++ b/include/linux/marker.h
@@ -0,0 +1,221 @@
+#ifndef _LINUX_MARKER_H
+#define _LINUX_MARKER_H
+
+/*
+ * Code markup for dynamic and static tracing.
+ *
+ * See Documentation/marker.txt.
+ *
+ * (C) Copyright 2006 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
+#include <stdarg.h>
+#include <linux/types.h>
+
+struct module;
+struct marker;
+
+/**
+ * marker_probe_func - Type of a marker probe function
+ * @probe_private: probe private data
+ * @call_private: call site private data
+ * @fmt: format string
+ * @args: variable argument list pointer. Use a pointer to overcome C's
+ *        inability to pass this around as a pointer in a portable manner in
+ *        the callee otherwise.
+ *
+ * Type of marker probe functions. They receive the mdata and need to parse the
+ * format string to recover the variable argument list.
+ */
+typedef void marker_probe_func(void *probe_private, void *call_private,
+		const char *fmt, va_list *args);
+
+struct marker_probe_closure {
+	marker_probe_func *func;	/* Callback */
+	void *probe_private;		/* Private probe data */
+};
+
+struct marker {
+	const char *name;	/* Marker name */
+	const char *format;	/* Marker format string, describing the
+				 * variable argument list.
+				 */
+	char state;		/* Marker state. */
+	char ptype;		/* probe type : 0 : single, 1 : multi */
+				/* Probe wrapper */
+	void (*call)(const struct marker *mdata, void *call_private, ...);
+	struct marker_probe_closure single;
+	struct marker_probe_closure *multi;
+	const char *tp_name;	/* Optional tracepoint name */
+	void *tp_cb;		/* Optional tracepoint callback */
+} __attribute__((aligned(8)));
+
+#ifdef CONFIG_MARKERS
+
+#define _DEFINE_MARKER(name, tp_name_str, tp_cb, format)		\
+		static const char __mstrtab_##name[]			\
+		__attribute__((section("__markers_strings")))		\
+		= #name "\0" format;					\
+		static struct marker __mark_##name			\
+		__attribute__((section("__markers"), aligned(8))) =	\
+		{ __mstrtab_##name, &__mstrtab_##name[sizeof(#name)],	\
+		  0, 0, marker_probe_cb, { __mark_empty_function, NULL},\
+		  NULL, tp_name_str, tp_cb }
+
+#define DEFINE_MARKER(name, format)					\
+		_DEFINE_MARKER(name, NULL, NULL, format)
+
+#define DEFINE_MARKER_TP(name, tp_name, tp_cb, format)			\
+		_DEFINE_MARKER(name, #tp_name, tp_cb, format)
+
+/*
+ * Note : the empty asm volatile with read constraint is used here instead of a
+ * "used" attribute to fix a gcc 4.1.x bug.
+ * Make sure the alignment of the structure in the __markers section will
+ * not add unwanted padding between the beginning of the section and the
+ * structure. Force alignment to the same alignment as the section start.
+ *
+ * The "generic" argument controls which marker enabling mechanism must be used.
+ * If generic is true, a variable read is used.
+ * If generic is false, immediate values are used.
+ */
+#define __trace_mark(generic, name, call_private, format, args...)	\
+	do {								\
+		DEFINE_MARKER(name, format);				\
+		__mark_check_format(format, ## args);			\
+		if (unlikely(__mark_##name.state)) {			\
+			(*__mark_##name.call)				\
+				(&__mark_##name, call_private, ## args);\
+		}							\
+	} while (0)
+
+#define __trace_mark_tp(name, call_private, tp_name, tp_cb, format, args...) \
+	do {								\
+		void __check_tp_type(void)				\
+		{							\
+			register_trace_##tp_name(tp_cb);		\
+		}							\
+		DEFINE_MARKER_TP(name, tp_name, tp_cb, format);		\
+		__mark_check_format(format, ## args);			\
+		(*__mark_##name.call)(&__mark_##name, call_private,	\
+					## args);			\
+	} while (0)
+
+extern void marker_update_probe_range(struct marker *begin,
+	struct marker *end);
+
+#define GET_MARKER(name)	(__mark_##name)
+
+#else /* !CONFIG_MARKERS */
+#define DEFINE_MARKER(name, tp_name, tp_cb, format)
+#define __trace_mark(generic, name, call_private, format, args...) \
+		__mark_check_format(format, ## args)
+#define __trace_mark_tp(name, call_private, tp_name, tp_cb, format, args...) \
+	do {								\
+		void __check_tp_type(void)				\
+		{							\
+			register_trace_##tp_name(tp_cb);		\
+		}							\
+		__mark_check_format(format, ## args);			\
+	} while (0)
+static inline void marker_update_probe_range(struct marker *begin,
+	struct marker *end)
+{ }
+#define GET_MARKER(name)
+#endif /* CONFIG_MARKERS */
+
+/**
+ * trace_mark - Marker using code patching
+ * @name: marker name, not quoted.
+ * @format: format string
+ * @args...: variable argument list
+ *
+ * Places a marker using optimized code patching technique (imv_read())
+ * to be enabled when immediate values are present.
+ */
+#define trace_mark(name, format, args...) \
+	__trace_mark(0, name, NULL, format, ## args)
+
+/**
+ * _trace_mark - Marker using variable read
+ * @name: marker name, not quoted.
+ * @format: format string
+ * @args...: variable argument list
+ *
+ * Places a marker using a standard memory read (_imv_read()) to be
+ * enabled. Should be used for markers in code paths where instruction
+ * modification based enabling is not welcome. (__init and __exit functions,
+ * lockdep, some traps, printk).
+ */
+#define _trace_mark(name, format, args...) \
+	__trace_mark(1, name, NULL, format, ## args)
+
+/**
+ * trace_mark_tp - Marker in a tracepoint callback
+ * @name: marker name, not quoted.
+ * @tp_name: tracepoint name, not quoted.
+ * @tp_cb: tracepoint callback. Should have an associated global symbol so it
+ *         is not optimized away by the compiler (should not be static).
+ * @format: format string
+ * @args...: variable argument list
+ *
+ * Places a marker in a tracepoint callback.
+ */
+#define trace_mark_tp(name, tp_name, tp_cb, format, args...)	\
+	__trace_mark_tp(name, NULL, tp_name, tp_cb, format, ## args)
+
+/**
+ * MARK_NOARGS - Format string for a marker with no argument.
+ */
+#define MARK_NOARGS " "
+
+/* To be used for string format validity checking with gcc */
+static inline void __printf(1, 2) ___mark_check_format(const char *fmt, ...)
+{
+}
+
+#define __mark_check_format(format, args...)				\
+	do {								\
+		if (0)							\
+			___mark_check_format(format, ## args);		\
+	} while (0)
+
+extern marker_probe_func __mark_empty_function;
+
+extern void marker_probe_cb(const struct marker *mdata,
+	void *call_private, ...);
+
+/*
+ * Connect a probe to a marker.
+ * private data pointer must be a valid allocated memory address, or NULL.
+ */
+extern int marker_probe_register(const char *name, const char *format,
+				marker_probe_func *probe, void *probe_private);
+
+/*
+ * Returns the private data given to marker_probe_register.
+ */
+extern int marker_probe_unregister(const char *name,
+	marker_probe_func *probe, void *probe_private);
+/*
+ * Unregister a marker by providing the registered private data.
+ */
+extern int marker_probe_unregister_private_data(marker_probe_func *probe,
+	void *probe_private);
+
+extern void *marker_get_private_data(const char *name, marker_probe_func *probe,
+	int num);
+
+/*
+ * marker_synchronize_unregister must be called between the last marker probe
+ * unregistration and the first one of
+ * - the end of module exit function
+ * - the free of any resource used by the probes
+ * to ensure the code and data are valid for any possibly running probes.
+ */
+#define marker_synchronize_unregister() synchronize_sched()
+
+#endif
diff --git a/include/linux/module.h b/include/linux/module.h
index 5de42043dff..11cb5f46cce 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -15,6 +15,7 @@
 #include <linux/stringify.h>
 #include <linux/kobject.h>
 #include <linux/moduleparam.h>
+#include <linux/marker.h>
 #include <linux/tracepoint.h>
 
 #include <linux/percpu.h>
@@ -376,6 +377,10 @@ struct module
 	/* The command line arguments (may be mangled).  People like
 	   keeping pointers to this stuff */
 	char *args;
+#ifdef CONFIG_MARKERS
+	struct marker *markers;
+	unsigned int num_markers;
+#endif
 #ifdef CONFIG_TRACEPOINTS
 	struct tracepoint * const *tracepoints_ptrs;
 	unsigned int num_tracepoints;
@@ -575,6 +580,8 @@ int unregister_module_notifier(struct notifier_block * nb);
 
 extern void print_modules(void);
 
+extern void module_update_markers(void);
+
 extern void module_update_tracepoints(void);
 extern int module_get_iter_tracepoints(struct tracepoint_iter *iter);
 
@@ -694,6 +701,10 @@ static inline void print_modules(void)
 {
 }
 
+static inline void module_update_markers(void)
+{
+}
+
 static inline void module_update_tracepoints(void)
 {
 }
diff --git a/init/Kconfig b/init/Kconfig
index 29cb97ef0bd..e3861029bc0 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1298,6 +1298,13 @@ config PROFILING
 config TRACEPOINTS
 	bool
 
+config MARKERS
+	bool "Activate markers"
+	select TRACEPOINTS
+	help
+	  Place an empty function call at each marker site. Can be
+	  dynamically changed for a probe function.
+
 source "arch/Kconfig"
 
 endmenu		# General setup
diff --git a/kernel/Makefile b/kernel/Makefile
index 0496be6eb95..c039580ba3b 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -91,6 +91,7 @@ obj-$(CONFIG_RELAY) += relay.o
 obj-$(CONFIG_SYSCTL) += utsname_sysctl.o
 obj-$(CONFIG_TASK_DELAY_ACCT) += delayacct.o
 obj-$(CONFIG_TASKSTATS) += taskstats.o tsacct.o
+obj-$(CONFIG_MARKERS) += marker.o
 obj-$(CONFIG_TRACEPOINTS) += tracepoint.o
 obj-$(CONFIG_LATENCYTOP) += latencytop.o
 obj-$(CONFIG_BINFMT_ELF) += elfcore.o
diff --git a/kernel/marker.c b/kernel/marker.c
new file mode 100644
index 00000000000..ea54f264786
--- /dev/null
+++ b/kernel/marker.c
@@ -0,0 +1,930 @@
+/*
+ * Copyright (C) 2007 Mathieu Desnoyers
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/types.h>
+#include <linux/jhash.h>
+#include <linux/list.h>
+#include <linux/rcupdate.h>
+#include <linux/marker.h>
+#include <linux/err.h>
+#include <linux/slab.h>
+
+extern struct marker __start___markers[];
+extern struct marker __stop___markers[];
+
+/* Set to 1 to enable marker debug output */
+static const int marker_debug;
+
+/*
+ * markers_mutex nests inside module_mutex. Markers mutex protects the builtin
+ * and module markers and the hash table.
+ */
+static DEFINE_MUTEX(markers_mutex);
+
+/*
+ * Marker hash table, containing the active markers.
+ * Protected by module_mutex.
+ */
+#define MARKER_HASH_BITS 6
+#define MARKER_TABLE_SIZE (1 << MARKER_HASH_BITS)
+static struct hlist_head marker_table[MARKER_TABLE_SIZE];
+
+/*
+ * Note about RCU :
+ * It is used to make sure every handler has finished using its private data
+ * between two consecutive operation (add or remove) on a given marker.  It is
+ * also used to delay the free of multiple probes array until a quiescent state
+ * is reached.
+ * marker entries modifications are protected by the markers_mutex.
+ */
+struct marker_entry {
+	struct hlist_node hlist;
+	char *format;
+			/* Probe wrapper */
+	void (*call)(const struct marker *mdata, void *call_private, ...);
+	struct marker_probe_closure single;
+	struct marker_probe_closure *multi;
+	int refcount;	/* Number of times armed. 0 if disarmed. */
+	struct rcu_head rcu;
+	void *oldptr;
+	int rcu_pending;
+	unsigned char ptype:1;
+	unsigned char format_allocated:1;
+	char name[0];	/* Contains name'\0'format'\0' */
+};
+
+/**
+ * __mark_empty_function - Empty probe callback
+ * @probe_private: probe private data
+ * @call_private: call site private data
+ * @fmt: format string
+ * @...: variable argument list
+ *
+ * Empty callback provided as a probe to the markers. By providing this to a
+ * disabled marker, we make sure the  execution flow is always valid even
+ * though the function pointer change and the marker enabling are two distinct
+ * operations that modifies the execution flow of preemptible code.
+ */
+notrace void __mark_empty_function(void *probe_private, void *call_private,
+	const char *fmt, va_list *args)
+{
+}
+EXPORT_SYMBOL_GPL(__mark_empty_function);
+
+/*
+ * marker_probe_cb Callback that prepares the variable argument list for probes.
+ * @mdata: pointer of type struct marker
+ * @call_private: caller site private data
+ * @...:  Variable argument list.
+ *
+ * Since we do not use "typical" pointer based RCU in the 1 argument case, we
+ * need to put a full smp_rmb() in this branch. This is why we do not use
+ * rcu_dereference() for the pointer read.
+ */
+notrace void marker_probe_cb(const struct marker *mdata,
+		void *call_private, ...)
+{
+	va_list args;
+	char ptype;
+
+	/*
+	 * rcu_read_lock_sched does two things : disabling preemption to make
+	 * sure the teardown of the callbacks can be done correctly when they
+	 * are in modules and they insure RCU read coherency.
+	 */
+	rcu_read_lock_sched_notrace();
+	ptype = mdata->ptype;
+	if (likely(!ptype)) {
+		marker_probe_func *func;
+		/* Must read the ptype before ptr. They are not data dependant,
+		 * so we put an explicit smp_rmb() here. */
+		smp_rmb();
+		func = mdata->single.func;
+		/* Must read the ptr before private data. They are not data
+		 * dependant, so we put an explicit smp_rmb() here. */
+		smp_rmb();
+		va_start(args, call_private);
+		func(mdata->single.probe_private, call_private, mdata->format,
+			&args);
+		va_end(args);
+	} else {
+		struct marker_probe_closure *multi;
+		int i;
+		/*
+		 * Read mdata->ptype before mdata->multi.
+		 */
+		smp_rmb();
+		multi = mdata->multi;
+		/*
+		 * multi points to an array, therefore accessing the array
+		 * depends on reading multi. However, even in this case,
+		 * we must insure that the pointer is read _before_ the array
+		 * data. Same as rcu_dereference, but we need a full smp_rmb()
+		 * in the fast path, so put the explicit barrier here.
+		 */
+		smp_read_barrier_depends();
+		for (i = 0; multi[i].func; i++) {
+			va_start(args, call_private);
+			multi[i].func(multi[i].probe_private, call_private,
+				mdata->format, &args);
+			va_end(args);
+		}
+	}
+	rcu_read_unlock_sched_notrace();
+}
+EXPORT_SYMBOL_GPL(marker_probe_cb);
+
+/*
+ * marker_probe_cb Callback that does not prepare the variable argument list.
+ * @mdata: pointer of type struct marker
+ * @call_private: caller site private data
+ * @...:  Variable argument list.
+ *
+ * Should be connected to markers "MARK_NOARGS".
+ */
+static notrace void marker_probe_cb_noarg(const struct marker *mdata,
+		void *call_private, ...)
+{
+	va_list args;	/* not initialized */
+	char ptype;
+
+	rcu_read_lock_sched_notrace();
+	ptype = mdata->ptype;
+	if (likely(!ptype)) {
+		marker_probe_func *func;
+		/* Must read the ptype before ptr. They are not data dependant,
+		 * so we put an explicit smp_rmb() here. */
+		smp_rmb();
+		func = mdata->single.func;
+		/* Must read the ptr before private data. They are not data
+		 * dependant, so we put an explicit smp_rmb() here. */
+		smp_rmb();
+		func(mdata->single.probe_private, call_private, mdata->format,
+			&args);
+	} else {
+		struct marker_probe_closure *multi;
+		int i;
+		/*
+		 * Read mdata->ptype before mdata->multi.
+		 */
+		smp_rmb();
+		multi = mdata->multi;
+		/*
+		 * multi points to an array, therefore accessing the array
+		 * depends on reading multi. However, even in this case,
+		 * we must insure that the pointer is read _before_ the array
+		 * data. Same as rcu_dereference, but we need a full smp_rmb()
+		 * in the fast path, so put the explicit barrier here.
+		 */
+		smp_read_barrier_depends();
+		for (i = 0; multi[i].func; i++)
+			multi[i].func(multi[i].probe_private, call_private,
+				mdata->format, &args);
+	}
+	rcu_read_unlock_sched_notrace();
+}
+
+static void free_old_closure(struct rcu_head *head)
+{
+	struct marker_entry *entry = container_of(head,
+		struct marker_entry, rcu);
+	kfree(entry->oldptr);
+	/* Make sure we free the data before setting the pending flag to 0 */
+	smp_wmb();
+	entry->rcu_pending = 0;
+}
+
+static void debug_print_probes(struct marker_entry *entry)
+{
+	int i;
+
+	if (!marker_debug)
+		return;
+
+	if (!entry->ptype) {
+		printk(KERN_DEBUG "Single probe : %p %p\n",
+			entry->single.func,
+			entry->single.probe_private);
+	} else {
+		for (i = 0; entry->multi[i].func; i++)
+			printk(KERN_DEBUG "Multi probe %d : %p %p\n", i,
+				entry->multi[i].func,
+				entry->multi[i].probe_private);
+	}
+}
+
+static struct marker_probe_closure *
+marker_entry_add_probe(struct marker_entry *entry,
+		marker_probe_func *probe, void *probe_private)
+{
+	int nr_probes = 0;
+	struct marker_probe_closure *old, *new;
+
+	WARN_ON(!probe);
+
+	debug_print_probes(entry);
+	old = entry->multi;
+	if (!entry->ptype) {
+		if (entry->single.func == probe &&
+				entry->single.probe_private == probe_private)
+			return ERR_PTR(-EBUSY);
+		if (entry->single.func == __mark_empty_function) {
+			/* 0 -> 1 probes */
+			entry->single.func = probe;
+			entry->single.probe_private = probe_private;
+			entry->refcount = 1;
+			entry->ptype = 0;
+			debug_print_probes(entry);
+			return NULL;
+		} else {
+			/* 1 -> 2 probes */
+			nr_probes = 1;
+			old = NULL;
+		}
+	} else {
+		/* (N -> N+1), (N != 0, 1) probes */
+		for (nr_probes = 0; old[nr_probes].func; nr_probes++)
+			if (old[nr_probes].func == probe
+					&& old[nr_probes].probe_private
+						== probe_private)
+				return ERR_PTR(-EBUSY);
+	}
+	/* + 2 : one for new probe, one for NULL func */
+	new = kzalloc((nr_probes + 2) * sizeof(struct marker_probe_closure),
+			GFP_KERNEL);
+	if (new == NULL)
+		return ERR_PTR(-ENOMEM);
+	if (!old)
+		new[0] = entry->single;
+	else
+		memcpy(new, old,
+			nr_probes * sizeof(struct marker_probe_closure));
+	new[nr_probes].func = probe;
+	new[nr_probes].probe_private = probe_private;
+	entry->refcount = nr_probes + 1;
+	entry->multi = new;
+	entry->ptype = 1;
+	debug_print_probes(entry);
+	return old;
+}
+
+static struct marker_probe_closure *
+marker_entry_remove_probe(struct marker_entry *entry,
+		marker_probe_func *probe, void *probe_private)
+{
+	int nr_probes = 0, nr_del = 0, i;
+	struct marker_probe_closure *old, *new;
+
+	old = entry->multi;
+
+	debug_print_probes(entry);
+	if (!entry->ptype) {
+		/* 0 -> N is an error */
+		WARN_ON(entry->single.func == __mark_empty_function);
+		/* 1 -> 0 probes */
+		WARN_ON(probe && entry->single.func != probe);
+		WARN_ON(entry->single.probe_private != probe_private);
+		entry->single.func = __mark_empty_function;
+		entry->refcount = 0;
+		entry->ptype = 0;
+		debug_print_probes(entry);
+		return NULL;
+	} else {
+		/* (N -> M), (N > 1, M >= 0) probes */
+		for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
+			if ((!probe || old[nr_probes].func == probe)
+					&& old[nr_probes].probe_private
+						== probe_private)
+				nr_del++;
+		}
+	}
+
+	if (nr_probes - nr_del == 0) {
+		/* N -> 0, (N > 1) */
+		entry->single.func = __mark_empty_function;
+		entry->refcount = 0;
+		entry->ptype = 0;
+	} else if (nr_probes - nr_del == 1) {
+		/* N -> 1, (N > 1) */
+		for (i = 0; old[i].func; i++)
+			if ((probe && old[i].func != probe) ||
+					old[i].probe_private != probe_private)
+				entry->single = old[i];
+		entry->refcount = 1;
+		entry->ptype = 0;
+	} else {
+		int j = 0;
+		/* N -> M, (N > 1, M > 1) */
+		/* + 1 for NULL */
+		new = kzalloc((nr_probes - nr_del + 1)
+			* sizeof(struct marker_probe_closure), GFP_KERNEL);
+		if (new == NULL)
+			return ERR_PTR(-ENOMEM);
+		for (i = 0; old[i].func; i++)
+			if ((probe && old[i].func != probe) ||
+					old[i].probe_private != probe_private)
+				new[j++] = old[i];
+		entry->refcount = nr_probes - nr_del;
+		entry->ptype = 1;
+		entry->multi = new;
+	}
+	debug_print_probes(entry);
+	return old;
+}
+
+/*
+ * Get marker if the marker is present in the marker hash table.
+ * Must be called with markers_mutex held.
+ * Returns NULL if not present.
+ */
+static struct marker_entry *get_marker(const char *name)
+{
+	struct hlist_head *head;
+	struct hlist_node *node;
+	struct marker_entry *e;
+	u32 hash = jhash(name, strlen(name), 0);
+
+	head = &marker_table[hash & ((1 << MARKER_HASH_BITS)-1)];
+	hlist_for_each_entry(e, node, head, hlist) {
+		if (!strcmp(name, e->name))
+			return e;
+	}
+	return NULL;
+}
+
+/*
+ * Add the marker to the marker hash table. Must be called with markers_mutex
+ * held.
+ */
+static struct marker_entry *add_marker(const char *name, const char *format)
+{
+	struct hlist_head *head;
+	struct hlist_node *node;
+	struct marker_entry *e;
+	size_t name_len = strlen(name) + 1;
+	size_t format_len = 0;
+	u32 hash = jhash(name, name_len-1, 0);
+
+	if (format)
+		format_len = strlen(format) + 1;
+	head = &marker_table[hash & ((1 << MARKER_HASH_BITS)-1)];
+	hlist_for_each_entry(e, node, head, hlist) {
+		if (!strcmp(name, e->name)) {
+			printk(KERN_NOTICE
+				"Marker %s busy\n", name);
+			return ERR_PTR(-EBUSY);	/* Already there */
+		}
+	}
+	/*
+	 * Using kmalloc here to allocate a variable length element. Could
+	 * cause some memory fragmentation if overused.
+	 */
+	e = kmalloc(sizeof(struct marker_entry) + name_len + format_len,
+			GFP_KERNEL);
+	if (!e)
+		return ERR_PTR(-ENOMEM);
+	memcpy(&e->name[0], name, name_len);
+	if (format) {
+		e->format = &e->name[name_len];
+		memcpy(e->format, format, format_len);
+		if (strcmp(e->format, MARK_NOARGS) == 0)
+			e->call = marker_probe_cb_noarg;
+		else
+			e->call = marker_probe_cb;
+		trace_mark(core_marker_format, "name %s format %s",
+				e->name, e->format);
+	} else {
+		e->format = NULL;
+		e->call = marker_probe_cb;
+	}
+	e->single.func = __mark_empty_function;
+	e->single.probe_private = NULL;
+	e->multi = NULL;
+	e->ptype = 0;
+	e->format_allocated = 0;
+	e->refcount = 0;
+	e->rcu_pending = 0;
+	hlist_add_head(&e->hlist, head);
+	return e;
+}
+
+/*
+ * Remove the marker from the marker hash table. Must be called with mutex_lock
+ * held.
+ */
+static int remove_marker(const char *name)
+{
+	struct hlist_head *head;
+	struct hlist_node *node;
+	struct marker_entry *e;
+	int found = 0;
+	size_t len = strlen(name) + 1;
+	u32 hash = jhash(name, len-1, 0);
+
+	head = &marker_table[hash & ((1 << MARKER_HASH_BITS)-1)];
+	hlist_for_each_entry(e, node, head, hlist) {
+		if (!strcmp(name, e->name)) {
+			found = 1;
+			break;
+		}
+	}
+	if (!found)
+		return -ENOENT;
+	if (e->single.func != __mark_empty_function)
+		return -EBUSY;
+	hlist_del(&e->hlist);
+	if (e->format_allocated)
+		kfree(e->format);
+	/* Make sure the call_rcu has been executed */
+	if (e->rcu_pending)
+		rcu_barrier_sched();
+	kfree(e);
+	return 0;
+}
+
+/*
+ * Set the mark_entry format to the format found in the element.
+ */
+static int marker_set_format(struct marker_entry *entry, const char *format)
+{
+	entry->format = kstrdup(format, GFP_KERNEL);
+	if (!entry->format)
+		return -ENOMEM;
+	entry->format_allocated = 1;
+
+	trace_mark(core_marker_format, "name %s format %s",
+			entry->name, entry->format);
+	return 0;
+}
+
+/*
+ * Sets the probe callback corresponding to one marker.
+ */
+static int set_marker(struct marker_entry *entry, struct marker *elem,
+		int active)
+{
+	int ret = 0;
+	WARN_ON(strcmp(entry->name, elem->name) != 0);
+
+	if (entry->format) {
+		if (strcmp(entry->format, elem->format) != 0) {
+			printk(KERN_NOTICE
+				"Format mismatch for probe %s "
+				"(%s), marker (%s)\n",
+				entry->name,
+				entry->format,
+				elem->format);
+			return -EPERM;
+		}
+	} else {
+		ret = marker_set_format(entry, elem->format);
+		if (ret)
+			return ret;
+	}
+
+	/*
+	 * probe_cb setup (statically known) is done here. It is
+	 * asynchronous with the rest of execution, therefore we only
+	 * pass from a "safe" callback (with argument) to an "unsafe"
+	 * callback (does not set arguments).
+	 */
+	elem->call = entry->call;
+	/*
+	 * Sanity check :
+	 * We only update the single probe private data when the ptr is
+	 * set to a _non_ single probe! (0 -> 1 and N -> 1, N != 1)
+	 */
+	WARN_ON(elem->single.func != __mark_empty_function
+		&& elem->single.probe_private != entry->single.probe_private
+		&& !elem->ptype);
+	elem->single.probe_private = entry->single.probe_private;
+	/*
+	 * Make sure the private data is valid when we update the
+	 * single probe ptr.
+	 */
+	smp_wmb();
+	elem->single.func = entry->single.func;
+	/*
+	 * We also make sure that the new probe callbacks array is consistent
+	 * before setting a pointer to it.
+	 */
+	rcu_assign_pointer(elem->multi, entry->multi);
+	/*
+	 * Update the function or multi probe array pointer before setting the
+	 * ptype.
+	 */
+	smp_wmb();
+	elem->ptype = entry->ptype;
+
+	if (elem->tp_name && (active ^ elem->state)) {
+		WARN_ON(!elem->tp_cb);
+		/*
+		 * It is ok to directly call the probe registration because type
+		 * checking has been done in the __trace_mark_tp() macro.
+		 */
+
+		if (active) {
+			/*
+			 * try_module_get should always succeed because we hold
+			 * lock_module() to get the tp_cb address.
+			 */
+			ret = try_module_get(__module_text_address(
+				(unsigned long)elem->tp_cb));
+			BUG_ON(!ret);
+			ret = tracepoint_probe_register_noupdate(
+				elem->tp_name,
+				elem->tp_cb);
+		} else {
+			ret = tracepoint_probe_unregister_noupdate(
+				elem->tp_name,
+				elem->tp_cb);
+			/*
+			 * tracepoint_probe_update_all() must be called
+			 * before the module containing tp_cb is unloaded.
+			 */
+			module_put(__module_text_address(
+				(unsigned long)elem->tp_cb));
+		}
+	}
+	elem->state = active;
+
+	return ret;
+}
+
+/*
+ * Disable a marker and its probe callback.
+ * Note: only waiting an RCU period after setting elem->call to the empty
+ * function insures that the original callback is not used anymore. This insured
+ * by rcu_read_lock_sched around the call site.
+ */
+static void disable_marker(struct marker *elem)
+{
+	int ret;
+
+	/* leave "call" as is. It is known statically. */
+	if (elem->tp_name && elem->state) {
+		WARN_ON(!elem->tp_cb);
+		/*
+		 * It is ok to directly call the probe registration because type
+		 * checking has been done in the __trace_mark_tp() macro.
+		 */
+		ret = tracepoint_probe_unregister_noupdate(elem->tp_name,
+			elem->tp_cb);
+		WARN_ON(ret);
+		/*
+		 * tracepoint_probe_update_all() must be called
+		 * before the module containing tp_cb is unloaded.
+		 */
+		module_put(__module_text_address((unsigned long)elem->tp_cb));
+	}
+	elem->state = 0;
+	elem->single.func = __mark_empty_function;
+	/* Update the function before setting the ptype */
+	smp_wmb();
+	elem->ptype = 0;	/* single probe */
+	/*
+	 * Leave the private data and id there, because removal is racy and
+	 * should be done only after an RCU period. These are never used until
+	 * the next initialization anyway.
+	 */
+}
+
+/**
+ * marker_update_probe_range - Update a probe range
+ * @begin: beginning of the range
+ * @end: end of the range
+ *
+ * Updates the probe callback corresponding to a range of markers.
+ */
+void marker_update_probe_range(struct marker *begin,
+	struct marker *end)
+{
+	struct marker *iter;
+	struct marker_entry *mark_entry;
+
+	mutex_lock(&markers_mutex);
+	for (iter = begin; iter < end; iter++) {
+		mark_entry = get_marker(iter->name);
+		if (mark_entry) {
+			set_marker(mark_entry, iter, !!mark_entry->refcount);
+			/*
+			 * ignore error, continue
+			 */
+		} else {
+			disable_marker(iter);
+		}
+	}
+	mutex_unlock(&markers_mutex);
+}
+
+/*
+ * Update probes, removing the faulty probes.
+ *
+ * Internal callback only changed before the first probe is connected to it.
+ * Single probe private data can only be changed on 0 -> 1 and 2 -> 1
+ * transitions.  All other transitions will leave the old private data valid.
+ * This makes the non-atomicity of the callback/private data updates valid.
+ *
+ * "special case" updates :
+ * 0 -> 1 callback
+ * 1 -> 0 callback
+ * 1 -> 2 callbacks
+ * 2 -> 1 callbacks
+ * Other updates all behave the same, just like the 2 -> 3 or 3 -> 2 updates.
+ * Site effect : marker_set_format may delete the marker entry (creating a
+ * replacement).
+ */
+static void marker_update_probes(void)
+{
+	/* Core kernel markers */
+	marker_update_probe_range(__start___markers, __stop___markers);
+	/* Markers in modules. */
+	module_update_markers();
+	tracepoint_probe_update_all();
+}
+
+/**
+ * marker_probe_register -  Connect a probe to a marker
+ * @name: marker name
+ * @format: format string
+ * @probe: probe handler
+ * @probe_private: probe private data
+ *
+ * private data must be a valid allocated memory address, or NULL.
+ * Returns 0 if ok, error value on error.
+ * The probe address must at least be aligned on the architecture pointer size.
+ */
+int marker_probe_register(const char *name, const char *format,
+			marker_probe_func *probe, void *probe_private)
+{
+	struct marker_entry *entry;
+	int ret = 0;
+	struct marker_probe_closure *old;
+
+	mutex_lock(&markers_mutex);
+	entry = get_marker(name);
+	if (!entry) {
+		entry = add_marker(name, format);
+		if (IS_ERR(entry))
+			ret = PTR_ERR(entry);
+	} else if (format) {
+		if (!entry->format)
+			ret = marker_set_format(entry, format);
+		else if (strcmp(entry->format, format))
+			ret = -EPERM;
+	}
+	if (ret)
+		goto end;
+
+	/*
+	 * If we detect that a call_rcu is pending for this marker,
+	 * make sure it's executed now.
+	 */
+	if (entry->rcu_pending)
+		rcu_barrier_sched();
+	old = marker_entry_add_probe(entry, probe, probe_private);
+	if (IS_ERR(old)) {
+		ret = PTR_ERR(old);
+		goto end;
+	}
+	mutex_unlock(&markers_mutex);
+	marker_update_probes();
+	mutex_lock(&markers_mutex);
+	entry = get_marker(name);
+	if (!entry)
+		goto end;
+	if (entry->rcu_pending)
+		rcu_barrier_sched();
+	entry->oldptr = old;
+	entry->rcu_pending = 1;
+	/* write rcu_pending before calling the RCU callback */
+	smp_wmb();
+	call_rcu_sched(&entry->rcu, free_old_closure);
+end:
+	mutex_unlock(&markers_mutex);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(marker_probe_register);
+
+/**
+ * marker_probe_unregister -  Disconnect a probe from a marker
+ * @name: marker name
+ * @probe: probe function pointer
+ * @probe_private: probe private data
+ *
+ * Returns the private data given to marker_probe_register, or an ERR_PTR().
+ * We do not need to call a synchronize_sched to make sure the probes have
+ * finished running before doing a module unload, because the module unload
+ * itself uses stop_machine(), which insures that every preempt disabled section
+ * have finished.
+ */
+int marker_probe_unregister(const char *name,
+	marker_probe_func *probe, void *probe_private)
+{
+	struct marker_entry *entry;
+	struct marker_probe_closure *old;
+	int ret = -ENOENT;
+
+	mutex_lock(&markers_mutex);
+	entry = get_marker(name);
+	if (!entry)
+		goto end;
+	if (entry->rcu_pending)
+		rcu_barrier_sched();
+	old = marker_entry_remove_probe(entry, probe, probe_private);
+	mutex_unlock(&markers_mutex);
+	marker_update_probes();
+	mutex_lock(&markers_mutex);
+	entry = get_marker(name);
+	if (!entry)
+		goto end;
+	if (entry->rcu_pending)
+		rcu_barrier_sched();
+	entry->oldptr = old;
+	entry->rcu_pending = 1;
+	/* write rcu_pending before calling the RCU callback */
+	smp_wmb();
+	call_rcu_sched(&entry->rcu, free_old_closure);
+	remove_marker(name);	/* Ignore busy error message */
+	ret = 0;
+end:
+	mutex_unlock(&markers_mutex);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(marker_probe_unregister);
+
+static struct marker_entry *
+get_marker_from_private_data(marker_probe_func *probe, void *probe_private)
+{
+	struct marker_entry *entry;
+	unsigned int i;
+	struct hlist_head *head;
+	struct hlist_node *node;
+
+	for (i = 0; i < MARKER_TABLE_SIZE; i++) {
+		head = &marker_table[i];
+		hlist_for_each_entry(entry, node, head, hlist) {
+			if (!entry->ptype) {
+				if (entry->single.func == probe
+						&& entry->single.probe_private
+						== probe_private)
+					return entry;
+			} else {
+				struct marker_probe_closure *closure;
+				closure = entry->multi;
+				for (i = 0; closure[i].func; i++) {
+					if (closure[i].func == probe &&
+							closure[i].probe_private
+							== probe_private)
+						return entry;
+				}
+			}
+		}
+	}
+	return NULL;
+}
+
+/**
+ * marker_probe_unregister_private_data -  Disconnect a probe from a marker
+ * @probe: probe function
+ * @probe_private: probe private data
+ *
+ * Unregister a probe by providing the registered private data.
+ * Only removes the first marker found in hash table.
+ * Return 0 on success or error value.
+ * We do not need to call a synchronize_sched to make sure the probes have
+ * finished running before doing a module unload, because the module unload
+ * itself uses stop_machine(), which insures that every preempt disabled section
+ * have finished.
+ */
+int marker_probe_unregister_private_data(marker_probe_func *probe,
+		void *probe_private)
+{
+	struct marker_entry *entry;
+	int ret = 0;
+	struct marker_probe_closure *old;
+
+	mutex_lock(&markers_mutex);
+	entry = get_marker_from_private_data(probe, probe_private);
+	if (!entry) {
+		ret = -ENOENT;
+		goto end;
+	}
+	if (entry->rcu_pending)
+		rcu_barrier_sched();
+	old = marker_entry_remove_probe(entry, NULL, probe_private);
+	mutex_unlock(&markers_mutex);
+	marker_update_probes();
+	mutex_lock(&markers_mutex);
+	entry = get_marker_from_private_data(probe, probe_private);
+	if (!entry)
+		goto end;
+	if (entry->rcu_pending)
+		rcu_barrier_sched();
+	entry->oldptr = old;
+	entry->rcu_pending = 1;
+	/* write rcu_pending before calling the RCU callback */
+	smp_wmb();
+	call_rcu_sched(&entry->rcu, free_old_closure);
+	remove_marker(entry->name);	/* Ignore busy error message */
+end:
+	mutex_unlock(&markers_mutex);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(marker_probe_unregister_private_data);
+
+/**
+ * marker_get_private_data - Get a marker's probe private data
+ * @name: marker name
+ * @probe: probe to match
+ * @num: get the nth matching probe's private data
+ *
+ * Returns the nth private data pointer (starting from 0) matching, or an
+ * ERR_PTR.
+ * Returns the private data pointer, or an ERR_PTR.
+ * The private data pointer should _only_ be dereferenced if the caller is the
+ * owner of the data, or its content could vanish. This is mostly used to
+ * confirm that a caller is the owner of a registered probe.
+ */
+void *marker_get_private_data(const char *name, marker_probe_func *probe,
+		int num)
+{
+	struct hlist_head *head;
+	struct hlist_node *node;
+	struct marker_entry *e;
+	size_t name_len = strlen(name) + 1;
+	u32 hash = jhash(name, name_len-1, 0);
+	int i;
+
+	head = &marker_table[hash & ((1 << MARKER_HASH_BITS)-1)];
+	hlist_for_each_entry(e, node, head, hlist) {
+		if (!strcmp(name, e->name)) {
+			if (!e->ptype) {
+				if (num == 0 && e->single.func == probe)
+					return e->single.probe_private;
+			} else {
+				struct marker_probe_closure *closure;
+				int match = 0;
+				closure = e->multi;
+				for (i = 0; closure[i].func; i++) {
+					if (closure[i].func != probe)
+						continue;
+					if (match++ == num)
+						return closure[i].probe_private;
+				}
+			}
+			break;
+		}
+	}
+	return ERR_PTR(-ENOENT);
+}
+EXPORT_SYMBOL_GPL(marker_get_private_data);
+
+#ifdef CONFIG_MODULES
+
+int marker_module_notify(struct notifier_block *self,
+			 unsigned long val, void *data)
+{
+	struct module *mod = data;
+
+	switch (val) {
+	case MODULE_STATE_COMING:
+		marker_update_probe_range(mod->markers,
+			mod->markers + mod->num_markers);
+		break;
+	case MODULE_STATE_GOING:
+		marker_update_probe_range(mod->markers,
+			mod->markers + mod->num_markers);
+		break;
+	}
+	return 0;
+}
+
+struct notifier_block marker_module_nb = {
+	.notifier_call = marker_module_notify,
+	.priority = 0,
+};
+
+static int init_markers(void)
+{
+	return register_module_notifier(&marker_module_nb);
+}
+__initcall(init_markers);
+
+#endif /* CONFIG_MODULES */
diff --git a/kernel/module.c b/kernel/module.c
index 2da82ba2a14..51724f9b8e9 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2461,6 +2461,10 @@ static void find_module_sections(struct module *mod, struct load_info *info)
 				  sizeof(*mod->ctors), &mod->num_ctors);
 #endif
 
+#ifdef CONFIG_MARKERS
+	mod->markers = section_objs(info, "__markers",
+				    sizeof(*mod->markers), &mod->num_markers);
+#endif
 #ifdef CONFIG_TRACEPOINTS
 	mod->tracepoints_ptrs = section_objs(info, "__tracepoints_ptrs",
 					     sizeof(*mod->tracepoints_ptrs),
@@ -3418,6 +3422,20 @@ void module_layout(struct module *mod,
 EXPORT_SYMBOL(module_layout);
 #endif
 
+#ifdef CONFIG_MARKERS
+void module_update_markers(void)
+{
+	struct module *mod;
+
+	mutex_lock(&module_mutex);
+	list_for_each_entry(mod, &modules, list)
+		if (!mod->taints)
+			marker_update_probe_range(mod->markers,
+				mod->markers + mod->num_markers);
+	mutex_unlock(&module_mutex);
+}
+#endif
+
 #ifdef CONFIG_TRACEPOINTS
 void module_update_tracepoints(void)
 {
diff --git a/kernel/trace/trace_printk.c b/kernel/trace/trace_printk.c
index 2547d8813cf..687699d365a 100644
--- a/kernel/trace/trace_printk.c
+++ b/kernel/trace/trace_printk.c
@@ -11,6 +11,7 @@
 #include <linux/ftrace.h>
 #include <linux/string.h>
 #include <linux/module.h>
+#include <linux/marker.h>
 #include <linux/mutex.h>
 #include <linux/ctype.h>
 #include <linux/list.h>
diff --git a/samples/Kconfig b/samples/Kconfig
index e03cf0e374d..7b1eadec88a 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -5,6 +5,12 @@ menuconfig SAMPLES
 
 if SAMPLES
 
+config SAMPLE_MARKERS
+	tristate "Build markers examples -- loadable modules only"
+	depends on MARKERS && m
+	help
+	  This build markers example modules.
+
 config SAMPLE_TRACEPOINTS
 	tristate "Build tracepoints examples -- loadable modules only"
 	depends on TRACEPOINTS && m
diff --git a/samples/Makefile b/samples/Makefile
index f26c0959fd8..ab354640197 100644
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -1,4 +1,4 @@
 # Makefile for Linux samples code
 
 obj-$(CONFIG_SAMPLES)	+= kobject/ kprobes/ tracepoints/ trace_events/ \
-			   hw_breakpoint/ kfifo/ kdb/
+			   hw_breakpoint/ kfifo/ kdb/ markers/
diff --git a/samples/markers/Makefile b/samples/markers/Makefile
new file mode 100644
index 00000000000..6d7231265f0
--- /dev/null
+++ b/samples/markers/Makefile
@@ -0,0 +1,4 @@
+# builds the kprobes example kernel modules;
+# then to use one (as root):  insmod <module_name.ko>
+
+obj-$(CONFIG_SAMPLE_MARKERS) += probe-example.o marker-example.o
diff --git a/samples/markers/marker-example.c b/samples/markers/marker-example.c
new file mode 100644
index 00000000000..e9cd9c0bc84
--- /dev/null
+++ b/samples/markers/marker-example.c
@@ -0,0 +1,53 @@
+/* marker-example.c
+ *
+ * Executes a marker when /proc/marker-example is opened.
+ *
+ * (C) Copyright 2007 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
+#include <linux/module.h>
+#include <linux/marker.h>
+#include <linux/sched.h>
+#include <linux/proc_fs.h>
+
+struct proc_dir_entry *pentry_example;
+
+static int my_open(struct inode *inode, struct file *file)
+{
+	int i;
+
+	trace_mark(subsystem_event, "integer %d string %s", 123,
+		"example string");
+	for (i = 0; i < 10; i++)
+		trace_mark(subsystem_eventb, MARK_NOARGS);
+	return -EPERM;
+}
+
+static struct file_operations mark_ops = {
+	.open = my_open,
+};
+
+static int __init example_init(void)
+{
+	printk(KERN_ALERT "example init\n");
+	pentry_example = proc_create("marker-example", 0444, NULL, &mark_ops);
+	if (!pentry_example)
+		return -EPERM;
+	return 0;
+}
+
+static void __exit example_exit(void)
+{
+	printk(KERN_ALERT "example exit\n");
+	remove_proc_entry("marker-example", NULL);
+}
+
+module_init(example_init)
+module_exit(example_exit)
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Mathieu Desnoyers");
+MODULE_DESCRIPTION("Marker example");
diff --git a/samples/markers/probe-example.c b/samples/markers/probe-example.c
new file mode 100644
index 00000000000..2dfb3b32937
--- /dev/null
+++ b/samples/markers/probe-example.c
@@ -0,0 +1,92 @@
+/* probe-example.c
+ *
+ * Connects two functions to marker call sites.
+ *
+ * (C) Copyright 2007 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
+#include <linux/sched.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/marker.h>
+#include <asm/atomic.h>
+
+struct probe_data {
+	const char *name;
+	const char *format;
+	marker_probe_func *probe_func;
+};
+
+void probe_subsystem_event(void *probe_data, void *call_data,
+	const char *format, va_list *args)
+{
+	/* Declare args */
+	unsigned int value;
+	const char *mystr;
+
+	/* Assign args */
+	value = va_arg(*args, typeof(value));
+	mystr = va_arg(*args, typeof(mystr));
+
+	/* Call printk */
+	printk(KERN_INFO "Value %u, string %s\n", value, mystr);
+
+	/* or count, check rights, serialize data in a buffer */
+}
+
+atomic_t eventb_count = ATOMIC_INIT(0);
+
+void probe_subsystem_eventb(void *probe_data, void *call_data,
+	const char *format, va_list *args)
+{
+	/* Increment counter */
+	atomic_inc(&eventb_count);
+}
+
+static struct probe_data probe_array[] =
+{
+	{	.name = "subsystem_event",
+		.format = "integer %d string %s",
+		.probe_func = probe_subsystem_event },
+	{	.name = "subsystem_eventb",
+		.format = MARK_NOARGS,
+		.probe_func = probe_subsystem_eventb },
+};
+
+static int __init probe_init(void)
+{
+	int result;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(probe_array); i++) {
+		result = marker_probe_register(probe_array[i].name,
+				probe_array[i].format,
+				probe_array[i].probe_func, &probe_array[i]);
+		if (result)
+			printk(KERN_INFO "Unable to register probe %s\n",
+				probe_array[i].name);
+	}
+	return 0;
+}
+
+static void __exit probe_fini(void)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(probe_array); i++)
+		marker_probe_unregister(probe_array[i].name,
+			probe_array[i].probe_func, &probe_array[i]);
+	printk(KERN_INFO "Number of event b : %u\n",
+			atomic_read(&eventb_count));
+	marker_synchronize_unregister();
+}
+
+module_init(probe_init);
+module_exit(probe_fini);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Mathieu Desnoyers");
+MODULE_DESCRIPTION("SUBSYSTEM Probe");
diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index 7d22056582c..e0d2e063d91 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -13,6 +13,7 @@
 # 2) modpost is then used to
 # 3)  create one <module>.mod.c file pr. module
 # 4)  create one Module.symvers file with CRC for all exported symbols
+# 4a) [CONFIG_MARKERS] create one Module.markers file listing defined markers
 # 5) compile all <module>.mod.c files
 # 6) final link of the module to a <module.ko> file
 
@@ -58,6 +59,10 @@ include scripts/Makefile.lib
 
 kernelsymfile := $(objtree)/Module.symvers
 modulesymfile := $(firstword $(KBUILD_EXTMOD))/Module.symvers
+kernelmarkersfile := $(objtree)/Module.markers
+modulemarkersfile := $(firstword $(KBUILD_EXTMOD))/Module.markers
+
+markersfile = $(if $(KBUILD_EXTMOD),$(modulemarkersfile),$(kernelmarkersfile))
 
 # Step 1), find all modules listed in $(MODVERDIR)/
 __modules := $(sort $(shell grep -h '\.ko' /dev/null $(wildcard $(MODVERDIR)/*.mod)))
@@ -80,6 +85,8 @@ modpost = scripts/mod/modpost                    \
  $(if $(KBUILD_EXTRA_SYMBOLS), $(patsubst %, -e %,$(KBUILD_EXTRA_SYMBOLS))) \
  $(if $(KBUILD_EXTMOD),-o $(modulesymfile))      \
  $(if $(CONFIG_DEBUG_SECTION_MISMATCH),,-S)      \
+ $(if $(CONFIG_MARKERS),-K $(kernelmarkersfile)) \
+ $(if $(CONFIG_MARKERS),-M $(markersfile))	 \
  $(if $(KBUILD_EXTMOD)$(KBUILD_MODPOST_WARN),-w) \
  $(if $(cross_build),-c)
 
@@ -94,12 +101,17 @@ quiet_cmd_kernel-mod = MODPOST $@
       cmd_kernel-mod = $(modpost) $@
 
 vmlinux.o: FORCE
+	@rm -fr $(kernelmarkersfile)
 	$(call cmd,kernel-mod)
 
 # Declare generated files as targets for modpost
 $(symverfile):         __modpost ;
 $(modules:.ko=.mod.c): __modpost ;
 
+ifdef CONFIG_MARKERS
+$(markersfile):	       __modpost ;
+endif
+
 
 # Step 5), compile all *.mod.c files