Message-ID: <20061124220144.GM25048@Krystal>
Date:	Fri, 24 Nov 2006 17:01:44 -0500
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	linux-kernel@...r.kernel.org,
	Christoph Hellwig <hch@...radead.org>,
	Andrew Morton <akpm@...l.org>, Ingo Molnar <mingo@...hat.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Tom Zanussi <zanussi@...ibm.com>,
	Karim Yaghmour <karim@...rsys.com>,
	Paul Mundt <lethal@...ux-sh.org>, Jes Sorensen <jes@....com>,
	Richard J Moore <richardj_moore@...ibm.com>,
	"Martin J. Bligh" <mbligh@...igh.org>,
	Michel Dagenais <michel.dagenais@...ymtl.ca>,
	Douglas Niehaus <niehaus@...s.ku.edu>, ltt-dev@...fik.org,
	systemtap@...rces.redhat.com
Subject: [PATCH 12/16] LTTng 0.6.36 for 2.6.18 : Tracer module

LTTng tracer module.

patch12-2.6.18-lttng-core-0.6.36-tracer.diff

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

--BEGIN--
--- /dev/null
+++ b/ltt/ltt-tracer.c
@@ -0,0 +1,836 @@
+/*
+ * ltt-tracer.c
+ *
+ * (C) Copyright	2005-2006 -
+ * 		Mathieu Desnoyers (mathieu.desnoyers@...ymtl.ca)
+ *
+ * Contains the kernel code for the Linux Trace Toolkit.
+ *
+ * Author:
+ *	Mathieu Desnoyers (mathieu.desnoyers@...ymtl.ca)
+ *
+ * Inspired from LTT :
+ *	Karim Yaghmour (karim@...rsys.com)
+ *	Tom Zanussi (zanussi@...ibm.com)
+ *	Bob Wisniewski (bob@...son.ibm.com)
+ * And from K42 :
+ *  Bob Wisniewski (bob@...son.ibm.com)
+ *
+ * Changelog:
+ *  22/09/06 Move to the marker/probes mechanism. (Mathieu Desnoyers)
+ *  19/10/05, Complete lockless mechanism. (Mathieu Desnoyers)
+ *	27/05/05, Modular redesign and rewrite. (Mathieu Desnoyers)
+
+ * Comments :
+ * num_active_traces protects the functors. Changing the pointer is an atomic
+ * operation, but the functions can only be called when in tracing. It is then
+ * safe to unload a module in which sits a functor when no tracing is active.
+ *
+ * filter_control functor is protected by incrementing its module refcount.
+ * 
+ */
+
+#include <linux/config.h>
+#include <linux/time.h>
+#include <ltt/ltt-tracer.h>
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/ltt-facilities.h>
+#include <linux/rcupdate.h>
+#include <linux/sched.h>
+#include <linux/bitops.h>
+#include <linux/fs.h>
+#include <linux/cpu.h>
+#include <linux/kref.h>
+#include <asm/atomic.h>
+
+/* Traces list writer locking */
+DECLARE_MUTEX(ltt_traces_sem);
+
+static struct timer_list ltt_async_wakeup_timer;
+
+/* Default callbacks for modules */
+int ltt_run_filter_default(void)
+{
+	return 1;
+}
+
+int ltt_filter_control_default
+	(enum ltt_filter_control_msg msg, struct ltt_trace_struct *trace)
+{
+	return 0;
+}
+
+int ltt_statedump_default(struct ltt_trace_struct *trace)
+{
+	return 0;
+}
+
+
+
+/* Callbacks for registered modules */
+
+int (*ltt_filter_control_functor)
+	(enum ltt_filter_control_msg msg, struct ltt_trace_struct *trace) =
+					ltt_filter_control_default;
+struct module *ltt_filter_control_owner = NULL;
+
+/* These function pointers are protected by trace activation check */
+
+int (*ltt_run_filter_functor)(void) = ltt_run_filter_default;
+struct module *ltt_run_filter_owner = NULL;
+
+// FIXME : integrate the filter in the logging chain.
+//
+int (*ltt_statedump_functor)(struct ltt_trace_struct *trace) = 
+					ltt_statedump_default;
+struct module *ltt_statedump_owner = NULL;
+					
+/* Module registration methods */
+
+int ltt_module_register(enum ltt_module_function name, void *function,
+		struct module *owner)
+{
+	int ret = 0;
+	
+	switch (name) {
+		case LTT_FUNCTION_RUN_FILTER:
+			if (ltt_run_filter_owner != NULL) {
+				ret = -EEXIST;
+				goto end;
+			}
+			ltt_run_filter_functor = (int (*)(void))function;
+			ltt_run_filter_owner = owner;
+			break;
+		case LTT_FUNCTION_FILTER_CONTROL:
+			if (ltt_filter_control_owner != NULL) {
+				ret = -EEXIST;
+				goto end;
+			}
+			ltt_filter_control_functor = 
+				(int (*)(enum ltt_filter_control_msg,
+				struct ltt_trace_struct *))function;
+			break;
+		case LTT_FUNCTION_STATEDUMP:
+			if (ltt_statedump_owner != NULL) {
+				ret = -EEXIST;
+				goto end;
+			}
+			ltt_statedump_functor = 
+				(int (*)(struct ltt_trace_struct *))function;
+			ltt_statedump_owner = owner;
+			break;
+	}
+
+end:
+
+	return ret;
+}
+
+
+void ltt_module_unregister(enum ltt_module_function name)
+{
+	switch (name) {
+		case LTT_FUNCTION_RUN_FILTER:
+			ltt_run_filter_functor = ltt_run_filter_default;
+			ltt_run_filter_owner = NULL;
+			/* Wait for preempt sections to finish */
+			synchronize_sched();
+			break;
+		case LTT_FUNCTION_FILTER_CONTROL:
+			ltt_filter_control_functor = ltt_filter_control_default;
+			ltt_filter_control_owner = NULL;
+			break;
+		case LTT_FUNCTION_STATEDUMP:
+			ltt_statedump_functor = ltt_statedump_default;
+			ltt_statedump_owner = NULL;
+			break;
+	}
+
+}
+
+EXPORT_SYMBOL_GPL(ltt_module_register);
+EXPORT_SYMBOL_GPL(ltt_module_unregister);
+
+static LIST_HEAD(ltt_transport_list);
+
+void ltt_transport_register(struct ltt_transport *transport)
+{
+	down(&ltt_traces_sem);
+	list_add_tail(&transport->node, &ltt_transport_list);
+	up(&ltt_traces_sem);
+}
+
+void ltt_transport_unregister(struct ltt_transport *transport)
+{
+	down(&ltt_traces_sem);
+	list_del(&transport->node);
+	up(&ltt_traces_sem);
+}
+
+EXPORT_SYMBOL_GPL(ltt_transport_register);
+EXPORT_SYMBOL_GPL(ltt_transport_unregister);
+
+
+static inline int is_channel_overwrite(enum ltt_channels chan,
+	enum trace_mode mode)
+{
+	switch (mode) {
+		case LTT_TRACE_NORMAL:
+			return 0;
+		case LTT_TRACE_FLIGHT:
+			switch (chan) {
+				case LTT_CHANNEL_FACILITIES:
+					return 0;
+				default:
+					return 1;
+			}
+		case LTT_TRACE_HYBRID:
+			switch (chan) {
+				case LTT_CHANNEL_CPU:
+					return 1;
+				default:
+					return 0;
+			}
+		default:
+			return 0;
+	}
+}
+
+
+void ltt_write_trace_header(struct ltt_trace_struct *trace,
+		struct ltt_trace_header *header)
+{
+	header->magic_number = LTT_TRACER_MAGIC_NUMBER;
+	header->major_version = LTT_TRACER_VERSION_MAJOR;
+	header->minor_version = LTT_TRACER_VERSION_MINOR;
+	header->float_word_order = 0;	 /* Kernel : no floating point */
+	header->arch_type = LTT_ARCH_TYPE;
+	header->arch_size = sizeof(void*);
+	header->arch_variant = LTT_ARCH_VARIANT;
+	switch (trace->mode) {
+		case LTT_TRACE_NORMAL:
+			header->flight_recorder = 0;
+			break;
+		case LTT_TRACE_FLIGHT:
+			header->flight_recorder = 1;
+			break;
+		case LTT_TRACE_HYBRID:
+			header->flight_recorder = 2;
+			break;
+		default:
+			header->flight_recorder = 0;
+	}
+	
+#ifdef CONFIG_LTT_HEARTBEAT_EVENT
+	header->has_heartbeat = 1;
+#else
+	header->has_heartbeat = 0;
+#endif //CONFIG_LTT_HEARTBEAT_EVENT
+
+#ifdef CONFIG_LTT_ALIGNMENT
+	header->has_alignment = sizeof(void*);
+#else
+	header->has_alignment = 0;
+#endif
+
+	header->freq_scale = trace->freq_scale;
+	header->start_freq = trace->start_freq;
+	header->start_tsc = trace->start_tsc;
+	header->start_monotonic = trace->start_monotonic;
+	header->start_time_sec = trace->start_time.tv_sec;
+	header->start_time_usec = trace->start_time.tv_usec;
+}
+EXPORT_SYMBOL_GPL(ltt_write_trace_header);
+
+static void trace_async_wakeup(struct ltt_trace_struct *trace)
+{
+	/* Must check each channel for pending read wakeup */
+	trace->ops->wakeup_channel(trace->channel.facilities);
+	trace->ops->wakeup_channel(trace->channel.interrupts);
+	trace->ops->wakeup_channel(trace->channel.processes);
+	trace->ops->wakeup_channel(trace->channel.modules);
+	trace->ops->wakeup_channel(trace->channel.cpu);
+	trace->ops->wakeup_channel(trace->channel.network);
+}
+
+/* Timer to send async wakeups to the readers */
+static void async_wakeup(unsigned long data)
+{
+	struct ltt_trace_struct *trace;
+	preempt_disable();
+	list_for_each_entry_rcu(trace, &ltt_traces.head, list) {
+		trace_async_wakeup(trace);
+	}
+	preempt_enable();
+
+	del_timer(&ltt_async_wakeup_timer);
+	ltt_async_wakeup_timer.expires = jiffies + 1;
+	add_timer(&ltt_async_wakeup_timer);
+}
+
+
+
+
+void ltt_wakeup_writers(void *private)
+{
+	struct ltt_channel_buf_struct *ltt_buf = private;
+	wake_up_interruptible(&ltt_buf->write_wait);
+}
+EXPORT_SYMBOL_GPL(ltt_wakeup_writers);
+
+
+/* _ltt_trace_find :
+ * find a trace by given name.
+ *
+ * Returns a pointer to the trace structure, NULL if not found. */
+static struct ltt_trace_struct *_ltt_trace_find(char *trace_name)
+{
+	int compare;
+	struct ltt_trace_struct *trace, *found=NULL;
+	
+	list_for_each_entry(trace, &ltt_traces.head, list) {
+		compare = strncmp(trace->trace_name, trace_name, NAME_MAX);
+
+		if (compare == 0) {
+			found = trace;
+			break;
+		}
+	}
+	
+	return found;
+}
+
+/* This function must be called with traces semaphore held. */
+static int _ltt_trace_create(char *trace_name,	enum trace_mode mode,
+				struct ltt_trace_struct *new_trace)
+{
+	int err = EPERM;
+
+	if (_ltt_trace_find(trace_name) != NULL) {
+		printk(KERN_ERR "LTT : Trace %s already exists\n", trace_name);
+		err = EEXIST;
+		goto traces_error;
+	}
+	list_add_rcu(&new_trace->list, &ltt_traces.head);
+	synchronize_sched();
+	/* Everything went fine, finish creation */
+	return 0;
+
+	/* Error handling */
+traces_error:
+	return err;
+}
+
+
+void ltt_release_transport(struct kref *kref)
+{
+	struct ltt_trace_struct *trace = container_of(kref,
+			struct ltt_trace_struct, ltt_transport_kref);
+	trace->ops->remove_dirs(trace);
+}
+EXPORT_SYMBOL_GPL(ltt_release_transport);
+
+
+void ltt_release_trace(struct kref *kref)
+{
+	struct ltt_trace_struct *trace = container_of(kref,
+			struct ltt_trace_struct, kref);
+	kfree(trace);
+}
+EXPORT_SYMBOL_GPL(ltt_release_trace);
+
+static inline void prepare_chan_size_num(unsigned *subbuf_size,
+	unsigned *n_subbufs, unsigned default_size, unsigned default_n_subbufs)
+{
+	if (*subbuf_size == 0)
+		*subbuf_size = default_size;
+	if (*n_subbufs == 0)
+		*n_subbufs = default_n_subbufs;
+	*subbuf_size = 1 << get_count_order(*subbuf_size);
+	*n_subbufs = 1 << get_count_order(*n_subbufs);
+
+	/* Subbuf size and number must both be power of two */
+	WARN_ON(hweight32(*subbuf_size) != 1);
+	WARN_ON(hweight32(*n_subbufs) != 1);
+}
+
+static int ltt_trace_create(char *trace_name, char *trace_type,
+		enum trace_mode mode,
+		unsigned subbuf_size_low, unsigned n_subbufs_low,
+		unsigned subbuf_size_med, unsigned n_subbufs_med,
+		unsigned subbuf_size_high, unsigned n_subbufs_high)
+{
+	int err = 0;
+	struct ltt_trace_struct *new_trace, *trace;
+	unsigned long flags;
+	struct ltt_transport *tran, *transport = NULL;
+	
+	prepare_chan_size_num(&subbuf_size_low, &n_subbufs_low,
+		LTT_DEFAULT_SUBBUF_SIZE_LOW, LTT_DEFAULT_N_SUBBUFS_LOW);
+
+	prepare_chan_size_num(&subbuf_size_med, &n_subbufs_med,
+		LTT_DEFAULT_SUBBUF_SIZE_MED, LTT_DEFAULT_N_SUBBUFS_MED);
+
+	prepare_chan_size_num(&subbuf_size_high, &n_subbufs_high,
+		LTT_DEFAULT_SUBBUF_SIZE_HIGH, LTT_DEFAULT_N_SUBBUFS_HIGH);
+
+	new_trace = kzalloc(sizeof(struct ltt_trace_struct), GFP_KERNEL);
+	if (!new_trace) {
+		printk(KERN_ERR
+			"LTT : Unable to allocate memory for trace %s\n",
+			trace_name);
+		err = ENOMEM;
+		goto traces_error;
+	}
+
+	kref_init(&new_trace->kref);
+	kref_init(&new_trace->ltt_transport_kref);
+	new_trace->active = 0;
+	strncpy(new_trace->trace_name, trace_name, NAME_MAX);
+	new_trace->paused = 0;
+	new_trace->mode = mode;
+	new_trace->freq_scale = ltt_freq_scale();
+
+	down(&ltt_traces_sem);
+	list_for_each_entry(tran, &ltt_transport_list, node) {
+		if (!strcmp(tran->name, trace_type)) {
+			transport = tran;
+			break;
+		}
+	}
+
+	if (!transport) {
+		err = EINVAL;
+		printk(KERN_ERR	"LTT : Transport %s is not present.\n", trace_type);
+		up(&ltt_traces_sem);
+		goto trace_error;
+	}
+
+	if (!try_module_get(transport->owner)) {
+		err = ENODEV;
+		printk(KERN_ERR	"LTT : Can't lock transport module.\n");
+		up(&ltt_traces_sem);
+		goto trace_error;
+	}
+
+	trace = _ltt_trace_find(trace_name);
+	if(trace) {
+		printk(KERN_ERR	"LTT : Trace name %s already used.\n",
+			trace_name);
+		err = EEXIST;
+		goto trace_error;
+	}
+
+	new_trace->transport = transport;
+	new_trace->ops = &transport->ops;
+
+	err = new_trace->ops->create_dirs(new_trace);
+	if (err)
+		goto dirs_error;
+
+	local_irq_save(flags);
+	new_trace->start_freq = ltt_frequency();
+	new_trace->start_tsc = ltt_get_timestamp64();
+	do_gettimeofday(&new_trace->start_time);
+	local_irq_restore(flags);
+	
+	/* Always put the facilities channel in non-overwrite mode :
+	 * This is a very low traffic channel and it can't afford to have its
+	 * data overwritten : this data (facilities info) is necessary to be
+	 * able to read the trace.
+	 *
+	 * WARNING : The heartbeat time _shouldn't_ write events in the
+	 * facilities channel as it would make the traffic too high. This is a
+	 * problematic case with flight recorder mode. FIXME
+	 */
+	err = new_trace->ops->create_channel(trace_name, new_trace,
+			new_trace->dentry.control_root, LTT_FACILITIES_CHANNEL,
+			&new_trace->channel.facilities, subbuf_size_low,
+			n_subbufs_low, is_channel_overwrite(LTT_CHANNEL_FACILITIES, mode));
+	if (err != 0) {
+		goto facilities_error;
+	}
+	err = new_trace->ops->create_channel(trace_name, new_trace,
+			new_trace->dentry.control_root, LTT_INTERRUPTS_CHANNEL,
+			&new_trace->channel.interrupts, subbuf_size_low,
+			n_subbufs_low, is_channel_overwrite(LTT_CHANNEL_INTERRUPTS, mode));
+	if (err != 0) {
+		goto interrupts_error;
+	}
+	err = new_trace->ops->create_channel(trace_name, new_trace,
+			new_trace->dentry.control_root, LTT_PROCESSES_CHANNEL,
+			&new_trace->channel.processes, subbuf_size_med,
+			n_subbufs_med, is_channel_overwrite(LTT_CHANNEL_PROCESSES, mode));
+	if (err != 0) {
+		goto processes_error;
+	}
+	err = new_trace->ops->create_channel(trace_name, new_trace,
+			new_trace->dentry.control_root, LTT_MODULES_CHANNEL,
+			&new_trace->channel.modules, subbuf_size_low,
+			n_subbufs_low, is_channel_overwrite(LTT_CHANNEL_MODULES, mode));
+	if (err != 0) {
+		goto modules_error;
+	}
+	err = new_trace->ops->create_channel(trace_name, new_trace,
+			new_trace->dentry.trace_root, LTT_CPU_CHANNEL,
+			&new_trace->channel.cpu, subbuf_size_high,
+			n_subbufs_high, is_channel_overwrite(LTT_CHANNEL_CPU, mode));
+	if (err != 0) {
+		goto cpu_error;
+	}
+	err = new_trace->ops->create_channel(trace_name, new_trace,
+			new_trace->dentry.control_root, LTT_NETWORK_CHANNEL,
+			&new_trace->channel.network, subbuf_size_low,
+			n_subbufs_low, is_channel_overwrite(LTT_CHANNEL_NETWORK, mode));
+	if (err != 0) {
+		goto network_error;
+	}
+	
+	err = _ltt_trace_create(trace_name, mode, new_trace);
+
+	if (err != 0)
+		goto lock_create_error;
+	up(&ltt_traces_sem);
+	return err;
+
+lock_create_error:
+	new_trace->ops->remove_channel(new_trace->channel.network);
+network_error:
+	new_trace->ops->remove_channel(new_trace->channel.cpu);
+cpu_error:
+	new_trace->ops->remove_channel(new_trace->channel.modules);
+modules_error:
+	new_trace->ops->remove_channel(new_trace->channel.processes);
+processes_error:
+	new_trace->ops->remove_channel(new_trace->channel.interrupts);
+interrupts_error:
+	new_trace->ops->remove_channel(new_trace->channel.facilities);
+facilities_error:
+	kref_put(&new_trace->ltt_transport_kref, ltt_release_transport);
+dirs_error:
+	module_put(transport->owner);
+trace_error:
+	kref_put(&new_trace->kref, ltt_release_trace);
+	up(&ltt_traces_sem);
+traces_error:
+	return err;
+}
+
+/* Must be called while sure that trace is in the list. */
+static int _ltt_trace_destroy(struct ltt_trace_struct	*trace)
+{
+	int err = EPERM;
+	
+	if (trace == NULL) {
+		err = ENOENT;
+		goto traces_error;
+	}
+	if (trace->active) {
+		printk(KERN_ERR
+			"LTT : Can't destroy trace %s : tracer is active\n",
+			trace->trace_name);
+		err = EBUSY;
+		goto active_error;
+	}
+	/* Everything went fine */
+	list_del_rcu(&trace->list);
+	synchronize_sched();
+	/* If no more trace in the list, we can free the unused facilities */
+	if (list_empty(&ltt_traces.head))
+		ltt_facility_free_unused();
+	return 0;
+
+	/* error handling */
+active_error:
+traces_error:
+	return err;
+}
+
+/* Sleepable part of the destroy */
+static void __ltt_trace_destroy(struct ltt_trace_struct	*trace)
+{
+	trace->ops->finish_channel(trace->channel.facilities);
+	trace->ops->finish_channel(trace->channel.interrupts);
+	trace->ops->finish_channel(trace->channel.processes);
+	trace->ops->finish_channel(trace->channel.modules);
+	trace->ops->finish_channel(trace->channel.cpu);
+	trace->ops->finish_channel(trace->channel.network);
+
+	flush_scheduled_work();
+
+	if (ltt_traces.num_active_traces == 0) {
+		/* We stop the asynchronous delivery of reader wakeup, but
+		 * we must make one last check for reader wakeups pending. */
+		del_timer(&ltt_async_wakeup_timer);
+	}
+	/* The currently destroyed trace is not in the trace list anymore,
+	 * so it's safe to call the async wakeup ourself. It will deliver
+	 * the last subbuffers. */
+	trace_async_wakeup(trace);
+
+	trace->ops->remove_channel(trace->channel.facilities);
+	trace->ops->remove_channel(trace->channel.interrupts);
+	trace->ops->remove_channel(trace->channel.processes);
+	trace->ops->remove_channel(trace->channel.modules);
+	trace->ops->remove_channel(trace->channel.cpu);
+	trace->ops->remove_channel(trace->channel.network);
+
+	kref_put(&trace->ltt_transport_kref, ltt_release_transport);
+
+	module_put(trace->transport->owner);
+
+	kref_put(&trace->kref, ltt_release_trace);
+}
+
+static int ltt_trace_destroy(char *trace_name)
+{
+	int err = 0;
+	struct ltt_trace_struct* trace;
+
+	down(&ltt_traces_sem);
+	trace = _ltt_trace_find(trace_name);
+	err = _ltt_trace_destroy(trace);
+	if (err)
+		goto error;
+	up(&ltt_traces_sem);
+	__ltt_trace_destroy(trace);
+	return err;
+
+	/* Error handling */
+error:
+	up(&ltt_traces_sem);
+	return err;
+}
+
+/* must be called from within a traces lock. */
+static int _ltt_trace_start(struct ltt_trace_struct* trace)
+{
+	int err = 0;
+
+	if (trace == NULL) {
+		err = ENOENT;
+		goto traces_error;
+	}
+	if (trace->active)
+		printk(KERN_INFO "LTT : Tracing already active for trace %s\n",
+				trace->trace_name);
+	if (!try_module_get(ltt_run_filter_owner)) {
+		err = ENODEV;
+		printk(KERN_ERR "LTT : Can't lock filter module.\n");
+		goto get_ltt_run_filter_error;
+	}
+	if (ltt_traces.num_active_traces == 0) {
+#ifdef CONFIG_LTT_HEARTBEAT
+		if (ltt_heartbeat_trigger(LTT_HEARTBEAT_START)) {
+			err = ENODEV;
+			printk(KERN_ERR
+				"LTT : Heartbeat timer module not present.\n");
+			goto ltt_heartbeat_error;
+		}
+#endif //CONFIG_LTT_HEARTBEAT
+		init_timer(&ltt_async_wakeup_timer);
+		ltt_async_wakeup_timer.function = async_wakeup;
+		ltt_async_wakeup_timer.expires = jiffies + 1;
+		add_timer(&ltt_async_wakeup_timer);
+	}
+	trace->active = 1;
+	ltt_traces.num_active_traces++;	/* Read by trace points without
+					 * protection : be careful */
+	return err;
+
+	/* error handling */
+#ifdef CONFIG_LTT_HEARTBEAT
+ltt_heartbeat_error:
+#endif //CONFIG_LTT_HEARTBEAT
+	module_put(ltt_run_filter_owner);
+get_ltt_run_filter_error:
+traces_error:
+	return err;
+}
+
+static int ltt_trace_start(char *trace_name)
+{
+	int err = 0;
+	struct ltt_trace_struct* trace;
+
+	down(&ltt_traces_sem);
+
+	trace = _ltt_trace_find(trace_name);
+	if (trace == NULL)
+		goto no_trace;
+	err = _ltt_trace_start(trace);
+
+	up(&ltt_traces_sem);
+	
+	/* Call the kernel state dump.
+	 * Events will be mixed with real kernel events, it's ok.
+	 * Notice that there is no protection on the trace : that's exactly
+	 * why we iterate on the list and check for trace equality instead of
+	 * directly using this trace handle inside the logging function. */
+	
+	ltt_facility_state_dump(trace);
+
+	if (!try_module_get(ltt_statedump_owner)) {
+		err = ENODEV;
+		printk(KERN_ERR
+			"LTT : Can't lock state dump module.\n");
+	} else {
+		ltt_statedump_functor(trace);
+		module_put(ltt_statedump_owner);
+	}
+
+	return err;
+
+	/* Error handling */
+no_trace:
+	up(&ltt_traces_sem);
+	return err;
+}
+
+
+/* must be called from within traces lock */
+static int _ltt_trace_stop(struct ltt_trace_struct* trace)
+{
+	int err = EPERM;
+
+	if (trace == NULL) {
+		err = ENOENT;
+		goto traces_error;
+	}
+	if (!trace->active)
+		printk(KERN_INFO "LTT : Tracing not active for trace %s\n",
+				trace->trace_name);
+	if (trace->active) {
+		trace->active = 0;
+		ltt_traces.num_active_traces--;
+		synchronize_sched(); /* Wait for each tracing to be finished */
+	}
+	if (ltt_traces.num_active_traces == 0) {
+#ifdef CONFIG_LTT_HEARTBEAT
+	/* stop the heartbeat if we are the last active trace */
+		ltt_heartbeat_trigger(LTT_HEARTBEAT_STOP);
+#endif //CONFIG_LTT_HEARTBEAT
+	}
+	module_put(ltt_run_filter_owner);
+	/* Everything went fine */
+	return 0;
+
+	/* Error handling */
+traces_error:
+	return err;
+}
+
+static int ltt_trace_stop(char *trace_name)
+{
+	int err = 0;
+	struct ltt_trace_struct* trace;
+
+	down(&ltt_traces_sem);
+	trace = _ltt_trace_find(trace_name);
+	err = _ltt_trace_stop(trace);
+	up(&ltt_traces_sem);
+	return err;
+}
+
+
+/* Exported functions */
+
+int ltt_control(enum ltt_control_msg msg, char *trace_name, char *trace_type,
+		union ltt_control_args args)
+{
+	int err = EPERM;
+	
+	printk(KERN_ALERT "ltt_control : trace %s\n", trace_name);
+	switch (msg) {
+		case LTT_CONTROL_START:
+			printk(KERN_DEBUG "Start tracing %s\n", trace_name);
+			err = ltt_trace_start(trace_name);
+			break;
+		case LTT_CONTROL_STOP:
+			printk(KERN_DEBUG "Stop tracing %s\n", trace_name);
+			err = ltt_trace_stop(trace_name);
+			break;
+		case LTT_CONTROL_CREATE_TRACE:
+			printk(KERN_DEBUG "Creating trace %s\n", trace_name);
+			err = ltt_trace_create(trace_name, trace_type,
+				args.new_trace.mode,
+				args.new_trace.subbuf_size_low,
+				args.new_trace.n_subbufs_low,
+				args.new_trace.subbuf_size_med,
+				args.new_trace.n_subbufs_med,
+				args.new_trace.subbuf_size_high,
+				args.new_trace.n_subbufs_high);
+			break;
+		case LTT_CONTROL_DESTROY_TRACE:
+			printk(KERN_DEBUG "Destroying trace %s\n", trace_name);
+			err = ltt_trace_destroy(trace_name);
+			break;
+	}
+	return err;
+}
+EXPORT_SYMBOL_GPL(ltt_control);
+
+int ltt_filter_control(enum ltt_filter_control_msg msg, char *trace_name)
+{
+	int err;
+	struct ltt_trace_struct *trace;
+
+	printk(KERN_DEBUG "ltt_filter_control : trace %s\n", trace_name);
+	down(&ltt_traces_sem);
+	trace = _ltt_trace_find(trace_name);
+	if (trace == NULL) {
+		printk(KERN_ALERT
+			"Trace does not exist. Cannot proxy control request\n");
+		err = ENOENT;
+		goto trace_error;
+	}
+	if (!try_module_get(ltt_filter_control_owner)) {
+		err = ENODEV;
+		goto get_module_error;
+	}
+	switch (msg) {
+		case LTT_FILTER_DEFAULT_ACCEPT:
+			printk(KERN_DEBUG
+				"Proxy filter default accept %s\n", trace_name);
+			err = (*ltt_filter_control_functor)(msg, trace);
+			break;
+		case LTT_FILTER_DEFAULT_REJECT:
+			printk(KERN_DEBUG
+				"Proxy filter default reject %s\n", trace_name);
+			err = (*ltt_filter_control_functor)(msg, trace);
+			break;
+		default:
+			err = EPERM;
+	}
+	module_put(ltt_filter_control_owner);
+	
+get_module_error:
+trace_error:
+	up(&ltt_traces_sem);
+	return err;
+}
+EXPORT_SYMBOL_GPL(ltt_filter_control);
+
+static void __exit ltt_exit(void)
+{
+	struct ltt_trace_struct *trace;
+	
+	down(&ltt_traces_sem);
+	/* Stop each trace and destroy them */
+	list_for_each_entry_rcu(trace, &ltt_traces.head, list) {
+		_ltt_trace_stop(trace);
+		_ltt_trace_destroy(trace);/* it's doing a synchronize_sched() */
+		__ltt_trace_destroy(trace);
+	}
+	up(&ltt_traces_sem);
+}
+
+module_exit(ltt_exit)
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Mathieu Desnoyers");
+MODULE_DESCRIPTION("Linux Trace Toolkit Next Generation Tracer");
+
--END--

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