[RFC patch 13/41] LTTng - tracer code

[Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>]

[-- Attachment #1: lttng-tracer.patch --]
[-- Type: text/plain, Size: 32122 bytes --]

Trace management code (API implementation). Home of the trace operation
synchronization.

Changelog :

In ltt_exit() the ltt_traces_sem is taken and list_for_each_entry_rcu is
> used. 
> 
> (There is another problem with the code I mention above. It's also
> appear to modify the list inside _ltt_trace_destroy, but your not doing
> a "safe" list traversal. So it should be list_for_each_entry_safe_rcu)
> 

This point is good, will fix.

Thanks to Daniel Walker (dwalker@mvista.com) for pointing this out.

Credits to Zhao Lei <zhaolei@cn.fujitsu.com> for a lot of fixes and extensions
which have been folded in this patch.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
CC: Zhao Lei <zhaolei@cn.fujitsu.com>
CC: Daniel Walker <dwalker@mvista.com>
---
 ltt/ltt-tracer.c | 1210 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 1210 insertions(+)

Index: linux-2.6-lttng/ltt/ltt-tracer.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6-lttng/ltt/ltt-tracer.c	2009-03-04 14:13:18.000000000 -0500
@@ -0,0 +1,1210 @@
+/*
+ * ltt/ltt-tracer.c
+ *
+ * (C) Copyright	2005-2008 -
+ * 		Mathieu Desnoyers (mathieu.desnoyers@polymtl.ca)
+ *
+ * Tracing management internal kernel API. Trace buffer allocation/free, tracing
+ * start/stop.
+ *
+ * Author:
+ *	Mathieu Desnoyers (mathieu.desnoyers@polymtl.ca)
+ *
+ * Inspired from LTT :
+ *  Karim Yaghmour (karim@opersys.com)
+ *  Tom Zanussi (zanussi@us.ibm.com)
+ *  Bob Wisniewski (bob@watson.ibm.com)
+ * And from K42 :
+ *  Bob Wisniewski (bob@watson.ibm.com)
+ *
+ * Changelog:
+ *  22/09/06, Move to the marker/probes mechanism.
+ *  19/10/05, Complete lockless mechanism.
+ *  27/05/05, Modular redesign and rewrite.
+ */
+
+#include <linux/time.h>
+#include <linux/ltt-tracer.h>
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/init.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 <linux/delay.h>
+#include <linux/vmalloc.h>
+#include <asm/atomic.h>
+
+static void async_wakeup(unsigned long data);
+
+static DEFINE_TIMER(ltt_async_wakeup_timer, async_wakeup, 0, 0);
+
+/* Default callbacks for modules */
+notrace 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;
+
+/* These function pointers are protected by a trace activation check */
+struct module *ltt_run_filter_owner;
+int (*ltt_statedump_functor)(struct ltt_trace_struct *trace) =
+					ltt_statedump_default;
+struct module *ltt_statedump_owner;
+
+struct chan_info_struct {
+	const char *name;
+	unsigned int def_subbufsize;
+	unsigned int def_subbufcount;
+} chan_infos[] = {
+	[LTT_CHANNEL_METADATA] = {
+		LTT_METADATA_CHANNEL,
+		LTT_DEFAULT_SUBBUF_SIZE_LOW,
+		LTT_DEFAULT_N_SUBBUFS_LOW,
+	},
+	[LTT_CHANNEL_FD_STATE] = {
+		LTT_FD_STATE_CHANNEL,
+		LTT_DEFAULT_SUBBUF_SIZE_LOW,
+		LTT_DEFAULT_N_SUBBUFS_LOW,
+	},
+	[LTT_CHANNEL_GLOBAL_STATE] = {
+		LTT_GLOBAL_STATE_CHANNEL,
+		LTT_DEFAULT_SUBBUF_SIZE_LOW,
+		LTT_DEFAULT_N_SUBBUFS_LOW,
+	},
+	[LTT_CHANNEL_IRQ_STATE] = {
+		LTT_IRQ_STATE_CHANNEL,
+		LTT_DEFAULT_SUBBUF_SIZE_LOW,
+		LTT_DEFAULT_N_SUBBUFS_LOW,
+	},
+	[LTT_CHANNEL_MODULE_STATE] = {
+		LTT_MODULE_STATE_CHANNEL,
+		LTT_DEFAULT_SUBBUF_SIZE_LOW,
+		LTT_DEFAULT_N_SUBBUFS_LOW,
+	},
+	[LTT_CHANNEL_NETIF_STATE] = {
+		LTT_NETIF_STATE_CHANNEL,
+		LTT_DEFAULT_SUBBUF_SIZE_LOW,
+		LTT_DEFAULT_N_SUBBUFS_LOW,
+	},
+	[LTT_CHANNEL_SOFTIRQ_STATE] = {
+		LTT_SOFTIRQ_STATE_CHANNEL,
+		LTT_DEFAULT_SUBBUF_SIZE_LOW,
+		LTT_DEFAULT_N_SUBBUFS_LOW,
+	},
+	[LTT_CHANNEL_SWAP_STATE] = {
+		LTT_SWAP_STATE_CHANNEL,
+		LTT_DEFAULT_SUBBUF_SIZE_LOW,
+		LTT_DEFAULT_N_SUBBUFS_LOW,
+	},
+	[LTT_CHANNEL_SYSCALL_STATE] = {
+		LTT_SYSCALL_STATE_CHANNEL,
+		LTT_DEFAULT_SUBBUF_SIZE_LOW,
+		LTT_DEFAULT_N_SUBBUFS_LOW,
+	},
+	[LTT_CHANNEL_TASK_STATE] = {
+		LTT_TASK_STATE_CHANNEL,
+		LTT_DEFAULT_SUBBUF_SIZE_LOW,
+		LTT_DEFAULT_N_SUBBUFS_LOW,
+	},
+	[LTT_CHANNEL_VM_STATE] = {
+		LTT_VM_STATE_CHANNEL,
+		LTT_DEFAULT_SUBBUF_SIZE_LOW,
+		LTT_DEFAULT_N_SUBBUFS_LOW,
+	},
+	[LTT_CHANNEL_FS] = {
+		LTT_FS_CHANNEL,
+		LTT_DEFAULT_SUBBUF_SIZE_MED,
+		LTT_DEFAULT_N_SUBBUFS_MED,
+	},
+	[LTT_CHANNEL_INPUT] = {
+		LTT_INPUT_CHANNEL,
+		LTT_DEFAULT_SUBBUF_SIZE_LOW,
+		LTT_DEFAULT_N_SUBBUFS_LOW,
+	},
+	[LTT_CHANNEL_IPC] = {
+		LTT_IPC_CHANNEL,
+		LTT_DEFAULT_SUBBUF_SIZE_LOW,
+		LTT_DEFAULT_N_SUBBUFS_LOW,
+	},
+	[LTT_CHANNEL_KERNEL] = {
+		LTT_KERNEL_CHANNEL,
+		LTT_DEFAULT_SUBBUF_SIZE_HIGH,
+		LTT_DEFAULT_N_SUBBUFS_HIGH,
+	},
+	[LTT_CHANNEL_MM] = {
+		LTT_MM_CHANNEL,
+		LTT_DEFAULT_SUBBUF_SIZE_MED,
+		LTT_DEFAULT_N_SUBBUFS_MED,
+	},
+	[LTT_CHANNEL_RCU] = {
+		LTT_RCU_CHANNEL,
+		LTT_DEFAULT_SUBBUF_SIZE_MED,
+		LTT_DEFAULT_N_SUBBUFS_MED,
+	},
+	[LTT_CHANNEL_DEFAULT] = {
+		NULL,
+		LTT_DEFAULT_SUBBUF_SIZE_MED,
+		LTT_DEFAULT_N_SUBBUFS_MED,
+	},
+};
+
+static enum ltt_channels get_channel_type_from_name(const char *name)
+{
+	int i;
+
+	if (!name)
+		return LTT_CHANNEL_DEFAULT;
+
+	for (i = 0; i < ARRAY_SIZE(chan_infos); i++)
+		if (chan_infos[i].name && !strcmp(name, chan_infos[i].name))
+			return (enum ltt_channels)i;
+
+	return LTT_CHANNEL_DEFAULT;
+}
+
+/**
+ * ltt_module_register - LTT module registration
+ * @name: module type
+ * @function: callback to register
+ * @owner: module which owns the callback
+ *
+ * The module calling this registration function must ensure that no
+ * trap-inducing code will be executed by "function". E.g. vmalloc_sync_all()
+ * must be called between a vmalloc and the moment the memory is made visible to
+ * "function". This registration acts as a vmalloc_sync_all. Therefore, only if
+ * the module allocates virtual memory after its registration must it
+ * synchronize the TLBs.
+ */
+int ltt_module_register(enum ltt_module_function name, void *function,
+		struct module *owner)
+{
+	int ret = 0;
+
+	/*
+	 * Make sure no page fault can be triggered by the module about to be
+	 * registered. We deal with this here so we don't have to call
+	 * vmalloc_sync_all() in each module's init.
+	 */
+	vmalloc_sync_all();
+
+	switch (name) {
+	case LTT_FUNCTION_RUN_FILTER:
+		if (ltt_run_filter_owner != NULL) {
+			ret = -EEXIST;
+			goto end;
+		}
+		ltt_filter_register((ltt_run_filter_functor)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;
+		ltt_filter_control_owner = owner;
+		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;
+}
+EXPORT_SYMBOL_GPL(ltt_module_register);
+
+/**
+ * ltt_module_unregister - LTT module unregistration
+ * @name: module type
+ */
+void ltt_module_unregister(enum ltt_module_function name)
+{
+	switch (name) {
+	case LTT_FUNCTION_RUN_FILTER:
+		ltt_filter_unregister();
+		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_unregister);
+
+static LIST_HEAD(ltt_transport_list);
+
+/**
+ * ltt_transport_register - LTT transport registration
+ * @transport: transport structure
+ *
+ * Registers a transport which can be used as output to extract the data out of
+ * LTTng. The module calling this registration function must ensure that no
+ * trap-inducing code will be executed by the transport functions. E.g.
+ * vmalloc_sync_all() must be called between a vmalloc and the moment the memory
+ * is made visible to the transport function. This registration acts as a
+ * vmalloc_sync_all. Therefore, only if the module allocates virtual memory
+ * after its registration must it synchronize the TLBs.
+ */
+void ltt_transport_register(struct ltt_transport *transport)
+{
+	/*
+	 * Make sure no page fault can be triggered by the module about to be
+	 * registered. We deal with this here so we don't have to call
+	 * vmalloc_sync_all() in each module's init.
+	 */
+	vmalloc_sync_all();
+
+	ltt_lock_traces();
+	list_add_tail(&transport->node, &ltt_transport_list);
+	ltt_unlock_traces();
+}
+EXPORT_SYMBOL_GPL(ltt_transport_register);
+
+/**
+ * ltt_transport_unregister - LTT transport unregistration
+ * @transport: transport structure
+ */
+void ltt_transport_unregister(struct ltt_transport *transport)
+{
+	ltt_lock_traces();
+	list_del(&transport->node);
+	ltt_unlock_traces();
+}
+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_METADATA:
+			return 0;
+		default:
+			return 1;
+		}
+	case LTT_TRACE_HYBRID:
+		switch (chan) {
+		case LTT_CHANNEL_KERNEL:
+		case LTT_CHANNEL_FS:
+		case LTT_CHANNEL_MM:
+		case LTT_CHANNEL_RCU:
+		case LTT_CHANNEL_IPC:
+		case LTT_CHANNEL_INPUT:
+			return 1;
+		default:
+			return 0;
+		}
+	default:
+		return 0;
+	}
+}
+
+/**
+ * ltt_write_trace_header - Write trace header
+ * @trace: Trace information
+ * @header: Memory address where the information must be written to
+ */
+void notrace ltt_write_trace_header(struct ltt_trace_struct *trace,
+		struct ltt_subbuffer_header *header)
+{
+	header->magic_number = LTT_TRACER_MAGIC_NUMBER;
+	header->major_version = LTT_TRACER_VERSION_MAJOR;
+	header->minor_version = LTT_TRACER_VERSION_MINOR;
+	header->arch_size = sizeof(void *);
+	header->alignment = ltt_get_alignment();
+	header->start_time_sec = trace->start_time.tv_sec;
+	header->start_time_usec = trace->start_time.tv_usec;
+	header->start_freq = trace->start_freq;
+	header->freq_scale = trace->freq_scale;
+}
+EXPORT_SYMBOL_GPL(ltt_write_trace_header);
+
+static void trace_async_wakeup(struct ltt_trace_struct *trace)
+{
+	int i;
+	struct ltt_channel_struct *chan;
+
+	/* Must check each channel for pending read wakeup */
+	for (i = 0; i < trace->nr_channels; i++) {
+		chan = &trace->channels[i];
+		if (chan->active)
+			trace->ops->wakeup_channel(chan);
+	}
+}
+
+/* Timer to send async wakeups to the readers */
+static void async_wakeup(unsigned long data)
+{
+	struct ltt_trace_struct *trace;
+	rcu_read_lock_sched();
+	list_for_each_entry_rcu(trace, &ltt_traces.head, list) {
+		trace_async_wakeup(trace);
+	}
+	rcu_read_unlock_sched();
+
+	mod_timer(&ltt_async_wakeup_timer, jiffies + LTT_PERCPU_TIMER_INTERVAL);
+}
+
+/**
+ * _ltt_trace_find - find a trace by given name.
+ * trace_name: trace name
+ *
+ * Returns a pointer to the trace structure, NULL if not found.
+ */
+static struct ltt_trace_struct *_ltt_trace_find(const char *trace_name)
+{
+	struct ltt_trace_struct *trace;
+
+	list_for_each_entry(trace, &ltt_traces.head, list)
+		if (!strncmp(trace->trace_name, trace_name, NAME_MAX))
+			return trace;
+
+	return NULL;
+}
+
+/* _ltt_trace_find_setup :
+ * find a trace in setup list by given name.
+ *
+ * Returns a pointer to the trace structure, NULL if not found.
+ */
+struct ltt_trace_struct *_ltt_trace_find_setup(const char *trace_name)
+{
+	struct ltt_trace_struct *trace;
+
+	list_for_each_entry(trace, &ltt_traces.setup_head, list)
+		if (!strncmp(trace->trace_name, trace_name, NAME_MAX))
+			return trace;
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(_ltt_trace_find_setup);
+
+/**
+ * ltt_release_transport - Release an LTT transport
+ * @kref : reference count on the transport
+ */
+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);
+
+/**
+ * ltt_release_trace - Release a LTT trace
+ * @kref : reference count on the trace
+ */
+void ltt_release_trace(struct kref *kref)
+{
+	struct ltt_trace_struct *trace = container_of(kref,
+			struct ltt_trace_struct, kref);
+	ltt_channels_trace_free(trace->channels);
+	kfree(trace);
+}
+EXPORT_SYMBOL_GPL(ltt_release_trace);
+
+static inline void prepare_chan_size_num(unsigned int *subbuf_size,
+					 unsigned int *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);
+}
+
+int _ltt_trace_setup(const char *trace_name)
+{
+	int err = 0;
+	struct ltt_trace_struct *new_trace = NULL;
+	int metadata_index;
+	unsigned int chan;
+	enum ltt_channels chantype;
+
+	if (_ltt_trace_find_setup(trace_name)) {
+		printk(KERN_ERR	"LTT : Trace name %s already used.\n",
+				trace_name);
+		err = -EEXIST;
+		goto traces_error;
+	}
+
+	if (_ltt_trace_find(trace_name)) {
+		printk(KERN_ERR	"LTT : Trace name %s already used.\n",
+				trace_name);
+		err = -EEXIST;
+		goto traces_error;
+	}
+
+	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;
+	}
+	strncpy(new_trace->trace_name, trace_name, NAME_MAX);
+	new_trace->channels = ltt_channels_trace_alloc(&new_trace->nr_channels,
+						       0, 1);
+	if (!new_trace->channels) {
+		printk(KERN_ERR
+			"LTT : Unable to allocate memory for chaninfo  %s\n",
+			trace_name);
+		err = -ENOMEM;
+		goto trace_free;
+	}
+
+	/*
+	 * Force metadata channel to active, no overwrite.
+	 */
+	metadata_index = ltt_channels_get_index_from_name("metadata");
+	WARN_ON(metadata_index < 0);
+	new_trace->channels[metadata_index].overwrite = 0;
+	new_trace->channels[metadata_index].active = 1;
+
+	/*
+	 * Set hardcoded tracer defaults for some channels
+	 */
+	for (chan = 0; chan < new_trace->nr_channels; chan++) {
+		if (!(new_trace->channels[chan].active))
+			continue;
+
+		chantype = get_channel_type_from_name(
+			ltt_channels_get_name_from_index(chan));
+		new_trace->channels[chan].subbuf_size =
+			chan_infos[chantype].def_subbufsize;
+		new_trace->channels[chan].subbuf_cnt =
+			chan_infos[chantype].def_subbufcount;
+	}
+
+	list_add(&new_trace->list, &ltt_traces.setup_head);
+	return 0;
+
+trace_free:
+	kfree(new_trace);
+traces_error:
+	return err;
+}
+EXPORT_SYMBOL_GPL(_ltt_trace_setup);
+
+
+int ltt_trace_setup(const char *trace_name)
+{
+	int ret;
+	ltt_lock_traces();
+	ret = _ltt_trace_setup(trace_name);
+	ltt_unlock_traces();
+	return ret;
+}
+EXPORT_SYMBOL_GPL(ltt_trace_setup);
+
+/* must be called from within a traces lock. */
+static void _ltt_trace_free(struct ltt_trace_struct *trace)
+{
+	list_del(&trace->list);
+	kfree(trace);
+}
+
+int ltt_trace_set_type(const char *trace_name, const char *trace_type)
+{
+	int err = 0;
+	struct ltt_trace_struct *trace;
+	struct ltt_transport *tran_iter, *transport = NULL;
+
+	ltt_lock_traces();
+
+	trace = _ltt_trace_find_setup(trace_name);
+	if (!trace) {
+		printk(KERN_ERR "LTT : Trace not found %s\n", trace_name);
+		err = -ENOENT;
+		goto traces_error;
+	}
+
+	list_for_each_entry(tran_iter, &ltt_transport_list, node) {
+		if (!strcmp(tran_iter->name, trace_type)) {
+			transport = tran_iter;
+			break;
+		}
+	}
+	if (!transport) {
+		printk(KERN_ERR	"LTT : Transport %s is not present.\n",
+			trace_type);
+		err = -EINVAL;
+		goto traces_error;
+	}
+
+	trace->transport = transport;
+
+traces_error:
+	ltt_unlock_traces();
+	return err;
+}
+EXPORT_SYMBOL_GPL(ltt_trace_set_type);
+
+int ltt_trace_set_channel_subbufsize(const char *trace_name,
+		const char *channel_name, unsigned int size)
+{
+	int err = 0;
+	struct ltt_trace_struct *trace;
+	int index;
+
+	ltt_lock_traces();
+
+	trace = _ltt_trace_find_setup(trace_name);
+	if (!trace) {
+		printk(KERN_ERR "LTT : Trace not found %s\n", trace_name);
+		err = -ENOENT;
+		goto traces_error;
+	}
+
+	index = ltt_channels_get_index_from_name(channel_name);
+	if (index < 0) {
+		printk(KERN_ERR "LTT : Channel %s not found\n", channel_name);
+		err = -ENOENT;
+		goto traces_error;
+	}
+	trace->channels[index].subbuf_size = size;
+
+traces_error:
+	ltt_unlock_traces();
+	return err;
+}
+EXPORT_SYMBOL_GPL(ltt_trace_set_channel_subbufsize);
+
+int ltt_trace_set_channel_subbufcount(const char *trace_name,
+		const char *channel_name, unsigned int cnt)
+{
+	int err = 0;
+	struct ltt_trace_struct *trace;
+	int index;
+
+	ltt_lock_traces();
+
+	trace = _ltt_trace_find_setup(trace_name);
+	if (!trace) {
+		printk(KERN_ERR "LTT : Trace not found %s\n", trace_name);
+		err = -ENOENT;
+		goto traces_error;
+	}
+
+	index = ltt_channels_get_index_from_name(channel_name);
+	if (index < 0) {
+		printk(KERN_ERR "LTT : Channel %s not found\n", channel_name);
+		err = -ENOENT;
+		goto traces_error;
+	}
+	trace->channels[index].subbuf_cnt = cnt;
+
+traces_error:
+	ltt_unlock_traces();
+	return err;
+}
+EXPORT_SYMBOL_GPL(ltt_trace_set_channel_subbufcount);
+
+int ltt_trace_set_channel_enable(const char *trace_name,
+		const char *channel_name, unsigned int enable)
+{
+	int err = 0;
+	struct ltt_trace_struct *trace;
+	int index;
+
+	ltt_lock_traces();
+
+	trace = _ltt_trace_find_setup(trace_name);
+	if (!trace) {
+		printk(KERN_ERR "LTT : Trace not found %s\n", trace_name);
+		err = -ENOENT;
+		goto traces_error;
+	}
+
+	/*
+	 * Datas in metadata channel(marker info) is necessary to be able to
+	 * read the trace, we always enable this channel.
+	 */
+	if (!enable && !strcmp(channel_name, "metadata")) {
+		printk(KERN_ERR "LTT : Trying to disable metadata channel\n");
+		err = -EINVAL;
+		goto traces_error;
+	}
+
+	index = ltt_channels_get_index_from_name(channel_name);
+	if (index < 0) {
+		printk(KERN_ERR "LTT : Channel %s not found\n", channel_name);
+		err = -ENOENT;
+		goto traces_error;
+	}
+
+	trace->channels[index].active = enable;
+
+traces_error:
+	ltt_unlock_traces();
+	return err;
+}
+EXPORT_SYMBOL_GPL(ltt_trace_set_channel_enable);
+
+int ltt_trace_set_channel_overwrite(const char *trace_name,
+		const char *channel_name, unsigned int overwrite)
+{
+	int err = 0;
+	struct ltt_trace_struct *trace;
+	int index;
+
+	ltt_lock_traces();
+
+	trace = _ltt_trace_find_setup(trace_name);
+	if (!trace) {
+		printk(KERN_ERR "LTT : Trace not found %s\n", trace_name);
+		err = -ENOENT;
+		goto traces_error;
+	}
+
+	/*
+	 * Always put the metadata channel in non-overwrite mode :
+	 * This is a very low traffic channel and it can't afford to have its
+	 * data overwritten : this data (marker info) is necessary to be
+	 * able to read the trace.
+	 */
+	if (overwrite && !strcmp(channel_name, "metadata")) {
+		printk(KERN_ERR "LTT : Trying to set metadata channel to "
+				"overwrite mode\n");
+		err = -EINVAL;
+		goto traces_error;
+	}
+
+	index = ltt_channels_get_index_from_name(channel_name);
+	if (index < 0) {
+		printk(KERN_ERR "LTT : Channel %s not found\n", channel_name);
+		err = -ENOENT;
+		goto traces_error;
+	}
+
+	trace->channels[index].overwrite = overwrite;
+
+traces_error:
+	ltt_unlock_traces();
+	return err;
+}
+EXPORT_SYMBOL_GPL(ltt_trace_set_channel_overwrite);
+
+int ltt_trace_alloc(const char *trace_name)
+{
+	int err = 0;
+	struct ltt_trace_struct *trace;
+	int subbuf_size, subbuf_cnt;
+	unsigned long flags;
+	int chan;
+	const char *channel_name;
+
+	ltt_lock_traces();
+
+	trace = _ltt_trace_find_setup(trace_name);
+	if (!trace) {
+		printk(KERN_ERR "LTT : Trace not found %s\n", trace_name);
+		err = -ENOENT;
+		goto traces_error;
+	}
+
+	kref_init(&trace->kref);
+	kref_init(&trace->ltt_transport_kref);
+	init_waitqueue_head(&trace->kref_wq);
+	trace->active = 0;
+	get_trace_clock();
+	trace->freq_scale = trace_clock_freq_scale();
+
+	if (!trace->transport) {
+		printk(KERN_ERR "LTT : Transport is not set.\n");
+		err = -EINVAL;
+		goto transport_error;
+	}
+	if (!try_module_get(trace->transport->owner)) {
+		printk(KERN_ERR	"LTT : Can't lock transport module.\n");
+		err = -ENODEV;
+		goto transport_error;
+	}
+	trace->ops = &trace->transport->ops;
+
+	err = trace->ops->create_dirs(trace);
+	if (err) {
+		printk(KERN_ERR	"LTT : Can't create dir for trace %s.\n",
+			trace_name);
+		goto dirs_error;
+	}
+
+	local_irq_save(flags);
+	trace->start_freq = trace_clock_frequency();
+	trace->start_tsc = trace_clock_read64();
+	do_gettimeofday(&trace->start_time);
+	local_irq_restore(flags);
+
+	for (chan = 0; chan < trace->nr_channels; chan++) {
+		if (!(trace->channels[chan].active))
+			continue;
+
+		channel_name = ltt_channels_get_name_from_index(chan);
+		WARN_ON(!channel_name);
+		subbuf_size = trace->channels[chan].subbuf_size;
+		subbuf_cnt = trace->channels[chan].subbuf_cnt;
+		prepare_chan_size_num(&subbuf_size, &subbuf_cnt);
+		err = trace->ops->create_channel(trace_name, trace,
+				trace->dentry.trace_root,
+				channel_name,
+				&trace->channels[chan],
+				subbuf_size,
+				subbuf_cnt,
+				trace->channels[chan].overwrite);
+		if (err != 0) {
+			printk(KERN_ERR	"LTT : Can't create channel %s.\n",
+				channel_name);
+			goto create_channel_error;
+		}
+	}
+
+	list_del(&trace->list);
+	if (list_empty(&ltt_traces.head)) {
+		mod_timer(&ltt_async_wakeup_timer,
+				jiffies + LTT_PERCPU_TIMER_INTERVAL);
+	}
+	list_add_rcu(&trace->list, &ltt_traces.head);
+	synchronize_sched();
+
+	ltt_unlock_traces();
+
+	return 0;
+
+create_channel_error:
+	for (chan--; chan >= 0; chan--)
+		if (trace->channels[chan].active)
+			trace->ops->remove_channel(&trace->channels[chan]);
+
+dirs_error:
+	module_put(trace->transport->owner);
+transport_error:
+	put_trace_clock();
+traces_error:
+	ltt_unlock_traces();
+	return err;
+}
+EXPORT_SYMBOL_GPL(ltt_trace_alloc);
+
+/*
+ * It is worked as a wrapper for current version of ltt_control.ko.
+ * We will make a new ltt_control based on debugfs, and control each channel's
+ * buffer.
+ */
+static int ltt_trace_create(const char *trace_name, const char *trace_type,
+		enum trace_mode mode,
+		unsigned int subbuf_size_low, unsigned int n_subbufs_low,
+		unsigned int subbuf_size_med, unsigned int n_subbufs_med,
+		unsigned int subbuf_size_high, unsigned int n_subbufs_high)
+{
+	int err = 0;
+
+	err = ltt_trace_setup(trace_name);
+	if (IS_ERR_VALUE(err))
+		return err;
+
+	err = ltt_trace_set_type(trace_name, trace_type);
+	if (IS_ERR_VALUE(err))
+		return err;
+
+	err = ltt_trace_alloc(trace_name);
+	if (IS_ERR_VALUE(err))
+		return err;
+
+	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 (list_empty(&ltt_traces.head)) {
+		/*
+		 * We stop the asynchronous delivery of reader wakeup, but
+		 * we must make one last check for reader wakeups pending
+		 * later in __ltt_trace_destroy.
+		 */
+		del_timer_sync(&ltt_async_wakeup_timer);
+	}
+	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)
+{
+	int i;
+	struct ltt_channel_struct *chan;
+
+	for (i = 0; i < trace->nr_channels; i++) {
+		chan = &trace->channels[i];
+		if (chan->active)
+			trace->ops->finish_channel(chan);
+	}
+
+	flush_scheduled_work();
+
+	/*
+	 * 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);
+
+	for (i = 0; i < trace->nr_channels; i++) {
+		chan = &trace->channels[i];
+		if (chan->active)
+			trace->ops->remove_channel(chan);
+	}
+
+	kref_put(&trace->ltt_transport_kref, ltt_release_transport);
+
+	module_put(trace->transport->owner);
+
+	/*
+	 * Wait for lttd readers to release the files, therefore making sure
+	 * the last subbuffers have been read.
+	 */
+	if (atomic_read(&trace->kref.refcount) > 1) {
+		int ret = 0;
+		__wait_event_interruptible(trace->kref_wq,
+			(atomic_read(&trace->kref.refcount) == 1), ret);
+	}
+	kref_put(&trace->kref, ltt_release_trace);
+}
+
+int ltt_trace_destroy(const char *trace_name)
+{
+	int err = 0;
+	struct ltt_trace_struct *trace;
+
+	ltt_lock_traces();
+
+	trace = _ltt_trace_find(trace_name);
+	if (trace) {
+		err = _ltt_trace_destroy(trace);
+		if (err)
+			goto error;
+
+		ltt_unlock_traces();
+
+		__ltt_trace_destroy(trace);
+		put_trace_clock();
+
+		return 0;
+	}
+
+	trace = _ltt_trace_find_setup(trace_name);
+	if (trace) {
+		_ltt_trace_free(trace);
+		ltt_unlock_traces();
+		return 0;
+	}
+
+	err = -ENOENT;
+
+	/* Error handling */
+error:
+	ltt_unlock_traces();
+	return err;
+}
+EXPORT_SYMBOL_GPL(ltt_trace_destroy);
+
+/* 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;
+	}
+	trace->active = 1;
+	/* Read by trace points without protection : be careful */
+	ltt_traces.num_active_traces++;
+	return err;
+
+	/* error handling */
+get_ltt_run_filter_error:
+traces_error:
+	return err;
+}
+
+int ltt_trace_start(const char *trace_name)
+{
+	int err = 0;
+	struct ltt_trace_struct *trace;
+
+	ltt_lock_traces();
+
+	trace = _ltt_trace_find(trace_name);
+	err = _ltt_trace_start(trace);
+	if (err)
+		goto no_trace;
+
+	ltt_unlock_traces();
+
+	/*
+	 * 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_dump_marker_state(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:
+	ltt_unlock_traces();
+	return err;
+}
+EXPORT_SYMBOL_GPL(ltt_trace_start);
+
+/* 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 */
+	}
+	module_put(ltt_run_filter_owner);
+	/* Everything went fine */
+	return 0;
+
+	/* Error handling */
+traces_error:
+	return err;
+}
+
+int ltt_trace_stop(const char *trace_name)
+{
+	int err = 0;
+	struct ltt_trace_struct *trace;
+
+	ltt_lock_traces();
+	trace = _ltt_trace_find(trace_name);
+	err = _ltt_trace_stop(trace);
+	ltt_unlock_traces();
+	return err;
+}
+EXPORT_SYMBOL_GPL(ltt_trace_stop);
+
+/**
+ * ltt_control - Trace control in-kernel API
+ * @msg: Action to perform
+ * @trace_name: Trace on which the action must be done
+ * @trace_type: Type of trace (normal, flight, hybrid)
+ * @args: Arguments specific to the action
+ */
+int ltt_control(enum ltt_control_msg msg, const char *trace_name,
+		const 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);
+
+/**
+ * ltt_filter_control - Trace filter control in-kernel API
+ * @msg: Action to perform on the filter
+ * @trace_name: Trace on which the action must be done
+ */
+int ltt_filter_control(enum ltt_filter_control_msg msg, const char *trace_name)
+{
+	int err;
+	struct ltt_trace_struct *trace;
+
+	printk(KERN_DEBUG "ltt_filter_control : trace %s\n", trace_name);
+	ltt_lock_traces();
+	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:
+	ltt_unlock_traces();
+	return err;
+}
+EXPORT_SYMBOL_GPL(ltt_filter_control);
+
+int __init ltt_init(void)
+{
+	/* Make sure no page fault can be triggered by this module */
+	vmalloc_sync_all();
+	return 0;
+}
+
+module_init(ltt_init)
+
+static void __exit ltt_exit(void)
+{
+	struct ltt_trace_struct *trace;
+	struct list_head *pos, *n;
+
+	ltt_lock_traces();
+	/* Stop each trace, currently being read by RCU read-side */
+	list_for_each_entry_rcu(trace, &ltt_traces.head, list)
+		_ltt_trace_stop(trace);
+	/* Wait for quiescent state. Readers have preemption disabled. */
+	synchronize_sched();
+	/* Safe iteration is now permitted. It does not have to be RCU-safe
+	 * because no readers are left. */
+	list_for_each_safe(pos, n, &ltt_traces.head) {
+		trace = container_of(pos, struct ltt_trace_struct, list);
+		/* _ltt_trace_destroy does a synchronize_sched() */
+		_ltt_trace_destroy(trace);
+		__ltt_trace_destroy(trace);
+	}
+	/* free traces in pre-alloc status */
+	list_for_each_safe(pos, n, &ltt_traces.setup_head) {
+		trace = container_of(pos, struct ltt_trace_struct, list);
+		_ltt_trace_free(trace);
+	}
+
+	ltt_unlock_traces();
+}
+
+module_exit(ltt_exit)
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Mathieu Desnoyers");
+MODULE_DESCRIPTION("Linux Trace Toolkit Next Generation Tracer Kernel API");

-- 
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68