X-Git-Url: http://git.lttng.org/?a=blobdiff_plain;f=libringbuffer%2Fring_buffer_frontend.c;h=5913f78d70a899fa78fd2409aded4f10723686b9;hb=abcabd6a23a42744beb0a80afee4104b690f23aa;hp=ecc72ab84f7e3143f930e77cac0bc6ad3de16a8e;hpb=852c29366c62c78f78af261f0287afcd92eae6b5;p=lttng-ust.git

diff --git a/libringbuffer/ring_buffer_frontend.c b/libringbuffer/ring_buffer_frontend.c
index ecc72ab8..5913f78d 100644
--- a/libringbuffer/ring_buffer_frontend.c
+++ b/libringbuffer/ring_buffer_frontend.c
@@ -1,7 +1,22 @@
 /*
  * ring_buffer_frontend.c
  *
- * (C) Copyright 2005-2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ * Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; only
+ * version 2.1 of the License.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ *
  *
  * Ring buffer wait-free buffer synchronization. Producer-consumer and flight
  * recorder (overwrite) modes. See thesis:
@@ -34,19 +49,47 @@
  *   - splice one subbuffer worth of data to a pipe
  *   - splice the data from pipe to disk/network
  *   - put_subbuf
- *
- * Dual LGPL v2.1/GPL v2 license.
  */
 
-#include <linux/delay.h>
-#include <linux/module.h>
-#include <linux/percpu.h>
+#define _GNU_SOURCE
+#include <sys/types.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <urcu/compiler.h>
+#include <urcu/ref.h>
+#include <helper.h>
+
+#include "smp.h"
+#include <lttng/ringbuffer-config.h>
+#include "vatomic.h"
+#include "backend.h"
+#include "frontend.h"
+#include "shm.h"
+#include "tlsfixup.h"
+
+#ifndef max
+#define max(a, b)	((a) > (b) ? (a) : (b))
+#endif
+
+/* Print DBG() messages about events lost only every 1048576 hits */
+#define DBG_PRINT_NR_LOST	(1UL << 20)
 
-#include "../../wrapper/ringbuffer/config.h"
-#include "../../wrapper/ringbuffer/backend.h"
-#include "../../wrapper/ringbuffer/frontend.h"
-#include "../../wrapper/ringbuffer/iterator.h"
-#include "../../wrapper/ringbuffer/nohz.h"
+/*
+ * Use POSIX SHM: shm_open(3) and shm_unlink(3).
+ * close(2) to close the fd returned by shm_open.
+ * shm_unlink releases the shared memory object name.
+ * ftruncate(2) sets the size of the memory object.
+ * mmap/munmap maps the shared memory obj to a virtual address in the
+ * calling proceess (should be done both in libust and consumer).
+ * See shm_overview(7) for details.
+ * Pass file descriptor returned by shm_open(3) to ltt-sessiond through
+ * a UNIX socket.
+ *
+ * Since we don't need to access the object using its name, we can
+ * immediately shm_unlink(3) it, and only keep the handle with its file
+ * descriptor.
+ */
 
 /*
  * Internal structure representing offsets to use at a sub-buffer switch.
@@ -58,38 +101,17 @@ struct switch_offsets {
 		     switch_old_end:1;
 };
 
-#ifdef CONFIG_NO_HZ
-enum tick_nohz_val {
-	TICK_NOHZ_STOP,
-	TICK_NOHZ_FLUSH,
-	TICK_NOHZ_RESTART,
-};
-
-static ATOMIC_NOTIFIER_HEAD(tick_nohz_notifier);
-#endif /* CONFIG_NO_HZ */
-
-static DEFINE_PER_CPU(spinlock_t, ring_buffer_nohz_lock);
-
-DEFINE_PER_CPU(unsigned int, lib_ring_buffer_nesting);
-EXPORT_PER_CPU_SYMBOL(lib_ring_buffer_nesting);
-
-static
-void lib_ring_buffer_print_errors(struct channel *chan,
-				  struct lib_ring_buffer *buf, int cpu);
+__thread unsigned int lib_ring_buffer_nesting;
 
 /*
- * Must be called under cpu hotplug protection.
+ * TODO: this is unused. Errors are saved within the ring buffer.
+ * Eventually, allow consumerd to print these errors.
  */
-void lib_ring_buffer_free(struct lib_ring_buffer *buf)
-{
-	struct channel *chan = buf->backend.chan;
-
-	lib_ring_buffer_print_errors(chan, buf, buf->backend.cpu);
-	kfree(buf->commit_hot);
-	kfree(buf->commit_cold);
-
-	lib_ring_buffer_backend_free(&buf->backend);
-}
+static
+void lib_ring_buffer_print_errors(struct channel *chan,
+				  struct lttng_ust_lib_ring_buffer *buf, int cpu,
+				  struct lttng_ust_shm_handle *handle)
+	__attribute__((unused));
 
 /**
  * lib_ring_buffer_reset - Reset ring buffer to initial values.
@@ -100,27 +122,27 @@ void lib_ring_buffer_free(struct lib_ring_buffer *buf)
  * should not be using the iterator concurrently with reset. The previous
  * current iterator record is reset.
  */
-void lib_ring_buffer_reset(struct lib_ring_buffer *buf)
+void lib_ring_buffer_reset(struct lttng_ust_lib_ring_buffer *buf,
+			   struct lttng_ust_shm_handle *handle)
 {
-	struct channel *chan = buf->backend.chan;
-	const struct lib_ring_buffer_config *config = chan->backend.config;
+	struct channel *chan = shmp(handle, buf->backend.chan);
+	const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
 	unsigned int i;
 
 	/*
 	 * Reset iterator first. It will put the subbuffer if it currently holds
 	 * it.
 	 */
-	lib_ring_buffer_iterator_reset(buf);
 	v_set(config, &buf->offset, 0);
 	for (i = 0; i < chan->backend.num_subbuf; i++) {
-		v_set(config, &buf->commit_hot[i].cc, 0);
-		v_set(config, &buf->commit_hot[i].seq, 0);
-		v_set(config, &buf->commit_cold[i].cc_sb, 0);
+		v_set(config, &shmp_index(handle, buf->commit_hot, i)->cc, 0);
+		v_set(config, &shmp_index(handle, buf->commit_hot, i)->seq, 0);
+		v_set(config, &shmp_index(handle, buf->commit_cold, i)->cc_sb, 0);
 	}
-	atomic_long_set(&buf->consumed, 0);
-	atomic_set(&buf->record_disabled, 0);
+	uatomic_set(&buf->consumed, 0);
+	uatomic_set(&buf->record_disabled, 0);
 	v_set(config, &buf->last_tsc, 0);
-	lib_ring_buffer_backend_reset(&buf->backend);
+	lib_ring_buffer_backend_reset(&buf->backend, handle);
 	/* Don't reset number of active readers */
 	v_set(config, &buf->records_lost_full, 0);
 	v_set(config, &buf->records_lost_wrap, 0);
@@ -129,7 +151,6 @@ void lib_ring_buffer_reset(struct lib_ring_buffer *buf)
 	v_set(config, &buf->records_overrun, 0);
 	buf->finalized = 0;
 }
-EXPORT_SYMBOL_GPL(lib_ring_buffer_reset);
 
 /**
  * channel_reset - Reset channel to initial values.
@@ -145,444 +166,257 @@ void channel_reset(struct channel *chan)
 	/*
 	 * Reset iterators first. Will put the subbuffer if held for reading.
 	 */
-	channel_iterator_reset(chan);
-	atomic_set(&chan->record_disabled, 0);
+	uatomic_set(&chan->record_disabled, 0);
 	/* Don't reset commit_count_mask, still valid */
 	channel_backend_reset(&chan->backend);
 	/* Don't reset switch/read timer interval */
 	/* Don't reset notifiers and notifier enable bits */
 	/* Don't reset reader reference count */
 }
-EXPORT_SYMBOL_GPL(channel_reset);
 
 /*
  * Must be called under cpu hotplug protection.
  */
-int lib_ring_buffer_create(struct lib_ring_buffer *buf,
-			   struct channel_backend *chanb, int cpu)
+int lib_ring_buffer_create(struct lttng_ust_lib_ring_buffer *buf,
+			   struct channel_backend *chanb, int cpu,
+			   struct lttng_ust_shm_handle *handle,
+			   struct shm_object *shmobj)
 {
-	const struct lib_ring_buffer_config *config = chanb->config;
-	struct channel *chan = container_of(chanb, struct channel, backend);
-	void *priv = chanb->priv;
-	unsigned int num_subbuf;
+	const struct lttng_ust_lib_ring_buffer_config *config = &chanb->config;
+	struct channel *chan = caa_container_of(chanb, struct channel, backend);
+	void *priv = channel_get_private(chan);
 	size_t subbuf_header_size;
-	u64 tsc;
+	uint64_t tsc;
 	int ret;
 
 	/* Test for cpu hotplug */
 	if (buf->backend.allocated)
 		return 0;
 
-	/*
-	 * Paranoia: per cpu dynamic allocation is not officially documented as
-	 * zeroing the memory, so let's do it here too, just in case.
-	 */
-	memset(buf, 0, sizeof(*buf));
-
-	ret = lib_ring_buffer_backend_create(&buf->backend, &chan->backend, cpu);
+	ret = lib_ring_buffer_backend_create(&buf->backend, &chan->backend,
+			cpu, handle, shmobj);
 	if (ret)
 		return ret;
 
-	buf->commit_hot =
-		kzalloc_node(ALIGN(sizeof(*buf->commit_hot)
-				   * chan->backend.num_subbuf,
-				   1 << INTERNODE_CACHE_SHIFT),
-			GFP_KERNEL, cpu_to_node(max(cpu, 0)));
-	if (!buf->commit_hot) {
+	align_shm(shmobj, __alignof__(struct commit_counters_hot));
+	set_shmp(buf->commit_hot,
+		 zalloc_shm(shmobj,
+			sizeof(struct commit_counters_hot) * chan->backend.num_subbuf));
+	if (!shmp(handle, buf->commit_hot)) {
 		ret = -ENOMEM;
 		goto free_chanbuf;
 	}
 
-	buf->commit_cold =
-		kzalloc_node(ALIGN(sizeof(*buf->commit_cold)
-				   * chan->backend.num_subbuf,
-				   1 << INTERNODE_CACHE_SHIFT),
-			GFP_KERNEL, cpu_to_node(max(cpu, 0)));
-	if (!buf->commit_cold) {
+	align_shm(shmobj, __alignof__(struct commit_counters_cold));
+	set_shmp(buf->commit_cold,
+		 zalloc_shm(shmobj,
+			sizeof(struct commit_counters_cold) * chan->backend.num_subbuf));
+	if (!shmp(handle, buf->commit_cold)) {
 		ret = -ENOMEM;
 		goto free_commit;
 	}
 
-	num_subbuf = chan->backend.num_subbuf;
-	init_waitqueue_head(&buf->read_wait);
-	raw_spin_lock_init(&buf->raw_tick_nohz_spinlock);
-
 	/*
 	 * Write the subbuffer header for first subbuffer so we know the total
 	 * duration of data gathering.
 	 */
 	subbuf_header_size = config->cb.subbuffer_header_size();
 	v_set(config, &buf->offset, subbuf_header_size);
-	subbuffer_id_clear_noref(config, &buf->backend.buf_wsb[0].id);
-	tsc = config->cb.ring_buffer_clock_read(buf->backend.chan);
-	config->cb.buffer_begin(buf, tsc, 0);
-	v_add(config, subbuf_header_size, &buf->commit_hot[0].cc);
+	subbuffer_id_clear_noref(config, &shmp_index(handle, buf->backend.buf_wsb, 0)->id);
+	tsc = config->cb.ring_buffer_clock_read(shmp(handle, buf->backend.chan));
+	config->cb.buffer_begin(buf, tsc, 0, handle);
+	v_add(config, subbuf_header_size, &shmp_index(handle, buf->commit_hot, 0)->cc);
 
 	if (config->cb.buffer_create) {
-		ret = config->cb.buffer_create(buf, priv, cpu, chanb->name);
+		ret = config->cb.buffer_create(buf, priv, cpu, chanb->name, handle);
 		if (ret)
 			goto free_init;
 	}
-
-	/*
-	 * Ensure the buffer is ready before setting it to allocated and setting
-	 * the cpumask.
-	 * Used for cpu hotplug vs cpumask iteration.
-	 */
-	smp_wmb();
 	buf->backend.allocated = 1;
-
-	if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
-		CHAN_WARN_ON(chan, cpumask_test_cpu(cpu,
-			     chan->backend.cpumask));
-		cpumask_set_cpu(cpu, chan->backend.cpumask);
-	}
-
 	return 0;
 
 	/* Error handling */
 free_init:
-	kfree(buf->commit_cold);
+	/* commit_cold will be freed by shm teardown */
 free_commit:
-	kfree(buf->commit_hot);
+	/* commit_hot will be freed by shm teardown */
 free_chanbuf:
-	lib_ring_buffer_backend_free(&buf->backend);
 	return ret;
 }
 
+#if 0
 static void switch_buffer_timer(unsigned long data)
 {
-	struct lib_ring_buffer *buf = (struct lib_ring_buffer *)data;
-	struct channel *chan = buf->backend.chan;
-	const struct lib_ring_buffer_config *config = chan->backend.config;
+	struct lttng_ust_lib_ring_buffer *buf = (struct lttng_ust_lib_ring_buffer *)data;
+	struct channel *chan = shmp(handle, buf->backend.chan);
+	const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
 
 	/*
 	 * Only flush buffers periodically if readers are active.
 	 */
-	if (atomic_long_read(&buf->active_readers))
-		lib_ring_buffer_switch_slow(buf, SWITCH_ACTIVE);
-
-	if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
-		mod_timer_pinned(&buf->switch_timer,
-				 jiffies + chan->switch_timer_interval);
-	else
-		mod_timer(&buf->switch_timer,
-			  jiffies + chan->switch_timer_interval);
+	if (uatomic_read(&buf->active_readers) || uatomic_read(&buf->active_shadow_readers))
+		lib_ring_buffer_switch_slow(buf, SWITCH_ACTIVE, handle);
+
+	//TODO timers
+	//if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
+	//	mod_timer_pinned(&buf->switch_timer,
+	//			 jiffies + chan->switch_timer_interval);
+	//else
+	//	mod_timer(&buf->switch_timer,
+	//		  jiffies + chan->switch_timer_interval);
 }
+#endif //0
 
-/*
- * Called with ring_buffer_nohz_lock held for per-cpu buffers.
- */
-static void lib_ring_buffer_start_switch_timer(struct lib_ring_buffer *buf)
+static void lib_ring_buffer_start_switch_timer(struct lttng_ust_lib_ring_buffer *buf,
+			   struct lttng_ust_shm_handle *handle)
 {
-	struct channel *chan = buf->backend.chan;
-	const struct lib_ring_buffer_config *config = chan->backend.config;
+	struct channel *chan = shmp(handle, buf->backend.chan);
+	//const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
 
 	if (!chan->switch_timer_interval || buf->switch_timer_enabled)
 		return;
-	init_timer(&buf->switch_timer);
-	buf->switch_timer.function = switch_buffer_timer;
-	buf->switch_timer.expires = jiffies + chan->switch_timer_interval;
-	buf->switch_timer.data = (unsigned long)buf;
-	if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
-		add_timer_on(&buf->switch_timer, buf->backend.cpu);
-	else
-		add_timer(&buf->switch_timer);
+	//TODO
+	//init_timer(&buf->switch_timer);
+	//buf->switch_timer.function = switch_buffer_timer;
+	//buf->switch_timer.expires = jiffies + chan->switch_timer_interval;
+	//buf->switch_timer.data = (unsigned long)buf;
+	//if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
+	//	add_timer_on(&buf->switch_timer, buf->backend.cpu);
+	//else
+	//	add_timer(&buf->switch_timer);
 	buf->switch_timer_enabled = 1;
 }
 
-/*
- * Called with ring_buffer_nohz_lock held for per-cpu buffers.
- */
-static void lib_ring_buffer_stop_switch_timer(struct lib_ring_buffer *buf)
+static void lib_ring_buffer_stop_switch_timer(struct lttng_ust_lib_ring_buffer *buf,
+			   struct lttng_ust_shm_handle *handle)
 {
-	struct channel *chan = buf->backend.chan;
+	struct channel *chan = shmp(handle, buf->backend.chan);
 
 	if (!chan->switch_timer_interval || !buf->switch_timer_enabled)
 		return;
 
-	del_timer_sync(&buf->switch_timer);
+	//TODO
+	//del_timer_sync(&buf->switch_timer);
 	buf->switch_timer_enabled = 0;
 }
 
+#if 0
 /*
  * Polling timer to check the channels for data.
  */
 static void read_buffer_timer(unsigned long data)
 {
-	struct lib_ring_buffer *buf = (struct lib_ring_buffer *)data;
-	struct channel *chan = buf->backend.chan;
-	const struct lib_ring_buffer_config *config = chan->backend.config;
+	struct lttng_ust_lib_ring_buffer *buf = (struct lttng_ust_lib_ring_buffer *)data;
+	struct channel *chan = shmp(handle, buf->backend.chan);
+	const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
 
 	CHAN_WARN_ON(chan, !buf->backend.allocated);
 
-	if (atomic_long_read(&buf->active_readers)
+	if (uatomic_read(&buf->active_readers) || uatomic_read(&buf->active_shadow_readers))
 	    && lib_ring_buffer_poll_deliver(config, buf, chan)) {
-		wake_up_interruptible(&buf->read_wait);
-		wake_up_interruptible(&chan->read_wait);
+		//TODO
+		//wake_up_interruptible(&buf->read_wait);
+		//wake_up_interruptible(&chan->read_wait);
 	}
 
-	if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
-		mod_timer_pinned(&buf->read_timer,
-				 jiffies + chan->read_timer_interval);
-	else
-		mod_timer(&buf->read_timer,
-			  jiffies + chan->read_timer_interval);
+	//TODO
+	//if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
+	//	mod_timer_pinned(&buf->read_timer,
+	//			 jiffies + chan->read_timer_interval);
+	//else
+	//	mod_timer(&buf->read_timer,
+	//		  jiffies + chan->read_timer_interval);
 }
+#endif //0
 
-/*
- * Called with ring_buffer_nohz_lock held for per-cpu buffers.
- */
-static void lib_ring_buffer_start_read_timer(struct lib_ring_buffer *buf)
+static void lib_ring_buffer_start_read_timer(struct lttng_ust_lib_ring_buffer *buf,
+			   struct lttng_ust_shm_handle *handle)
 {
-	struct channel *chan = buf->backend.chan;
-	const struct lib_ring_buffer_config *config = chan->backend.config;
+	struct channel *chan = shmp(handle, buf->backend.chan);
+	const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
 
 	if (config->wakeup != RING_BUFFER_WAKEUP_BY_TIMER
 	    || !chan->read_timer_interval
 	    || buf->read_timer_enabled)
 		return;
 
-	init_timer(&buf->read_timer);
-	buf->read_timer.function = read_buffer_timer;
-	buf->read_timer.expires = jiffies + chan->read_timer_interval;
-	buf->read_timer.data = (unsigned long)buf;
+	//TODO
+	//init_timer(&buf->read_timer);
+	//buf->read_timer.function = read_buffer_timer;
+	//buf->read_timer.expires = jiffies + chan->read_timer_interval;
+	//buf->read_timer.data = (unsigned long)buf;
 
-	if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
-		add_timer_on(&buf->read_timer, buf->backend.cpu);
-	else
-		add_timer(&buf->read_timer);
+	//if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
+	//	add_timer_on(&buf->read_timer, buf->backend.cpu);
+	//else
+	//	add_timer(&buf->read_timer);
 	buf->read_timer_enabled = 1;
 }
 
-/*
- * Called with ring_buffer_nohz_lock held for per-cpu buffers.
- */
-static void lib_ring_buffer_stop_read_timer(struct lib_ring_buffer *buf)
+static void lib_ring_buffer_stop_read_timer(struct lttng_ust_lib_ring_buffer *buf,
+			   struct lttng_ust_shm_handle *handle)
 {
-	struct channel *chan = buf->backend.chan;
-	const struct lib_ring_buffer_config *config = chan->backend.config;
+	struct channel *chan = shmp(handle, buf->backend.chan);
+	const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
 
 	if (config->wakeup != RING_BUFFER_WAKEUP_BY_TIMER
 	    || !chan->read_timer_interval
 	    || !buf->read_timer_enabled)
 		return;
 
-	del_timer_sync(&buf->read_timer);
+	//TODO
+	//del_timer_sync(&buf->read_timer);
 	/*
 	 * do one more check to catch data that has been written in the last
 	 * timer period.
 	 */
-	if (lib_ring_buffer_poll_deliver(config, buf, chan)) {
-		wake_up_interruptible(&buf->read_wait);
-		wake_up_interruptible(&chan->read_wait);
+	if (lib_ring_buffer_poll_deliver(config, buf, chan, handle)) {
+		//TODO
+		//wake_up_interruptible(&buf->read_wait);
+		//wake_up_interruptible(&chan->read_wait);
 	}
 	buf->read_timer_enabled = 0;
 }
 
-#ifdef CONFIG_HOTPLUG_CPU
-/**
- *	lib_ring_buffer_cpu_hp_callback - CPU hotplug callback
- *	@nb: notifier block
- *	@action: hotplug action to take
- *	@hcpu: CPU number
- *
- *	Returns the success/failure of the operation. (%NOTIFY_OK, %NOTIFY_BAD)
- */
-static
-int __cpuinit lib_ring_buffer_cpu_hp_callback(struct notifier_block *nb,
-					      unsigned long action,
-					      void *hcpu)
-{
-	unsigned int cpu = (unsigned long)hcpu;
-	struct channel *chan = container_of(nb, struct channel,
-					    cpu_hp_notifier);
-	struct lib_ring_buffer *buf = per_cpu_ptr(chan->backend.buf, cpu);
-	const struct lib_ring_buffer_config *config = chan->backend.config;
-
-	if (!chan->cpu_hp_enable)
-		return NOTIFY_DONE;
-
-	CHAN_WARN_ON(chan, config->alloc == RING_BUFFER_ALLOC_GLOBAL);
-
-	switch (action) {
-	case CPU_DOWN_FAILED:
-	case CPU_DOWN_FAILED_FROZEN:
-	case CPU_ONLINE:
-	case CPU_ONLINE_FROZEN:
-		wake_up_interruptible(&chan->hp_wait);
-		lib_ring_buffer_start_switch_timer(buf);
-		lib_ring_buffer_start_read_timer(buf);
-		return NOTIFY_OK;
-
-	case CPU_DOWN_PREPARE:
-	case CPU_DOWN_PREPARE_FROZEN:
-		lib_ring_buffer_stop_switch_timer(buf);
-		lib_ring_buffer_stop_read_timer(buf);
-		return NOTIFY_OK;
-
-	case CPU_DEAD:
-	case CPU_DEAD_FROZEN:
-		/*
-		 * Performing a buffer switch on a remote CPU. Performed by
-		 * the CPU responsible for doing the hotunplug after the target
-		 * CPU stopped running completely. Ensures that all data
-		 * from that remote CPU is flushed.
-		 */
-		lib_ring_buffer_switch_slow(buf, SWITCH_ACTIVE);
-		return NOTIFY_OK;
-
-	default:
-		return NOTIFY_DONE;
-	}
-}
-#endif
-
-#if defined(CONFIG_NO_HZ) && defined(CONFIG_LIB_RING_BUFFER)
-/*
- * For per-cpu buffers, call the reader wakeups before switching the buffer, so
- * that wake-up-tracing generated events are flushed before going idle (in
- * tick_nohz). We test if the spinlock is locked to deal with the race where
- * readers try to sample the ring buffer before we perform the switch. We let
- * the readers retry in that case. If there is data in the buffer, the wake up
- * is going to forbid the CPU running the reader thread from going idle.
- */
-static int notrace ring_buffer_tick_nohz_callback(struct notifier_block *nb,
-						  unsigned long val,
-						  void *data)
-{
-	struct channel *chan = container_of(nb, struct channel,
-					    tick_nohz_notifier);
-	const struct lib_ring_buffer_config *config = chan->backend.config;
-	struct lib_ring_buffer *buf;
-	int cpu = smp_processor_id();
-
-	if (config->alloc != RING_BUFFER_ALLOC_PER_CPU) {
-		/*
-		 * We don't support keeping the system idle with global buffers
-		 * and streaming active. In order to do so, we would need to
-		 * sample a non-nohz-cpumask racelessly with the nohz updates
-		 * without adding synchronization overhead to nohz. Leave this
-		 * use-case out for now.
-		 */
-		return 0;
-	}
-
-	buf = channel_get_ring_buffer(config, chan, cpu);
-	switch (val) {
-	case TICK_NOHZ_FLUSH:
-		raw_spin_lock(&buf->raw_tick_nohz_spinlock);
-		if (config->wakeup == RING_BUFFER_WAKEUP_BY_TIMER
-		    && chan->read_timer_interval
-		    && atomic_long_read(&buf->active_readers)
-		    && (lib_ring_buffer_poll_deliver(config, buf, chan)
-			|| lib_ring_buffer_pending_data(config, buf, chan))) {
-			wake_up_interruptible(&buf->read_wait);
-			wake_up_interruptible(&chan->read_wait);
-		}
-		if (chan->switch_timer_interval)
-			lib_ring_buffer_switch_slow(buf, SWITCH_ACTIVE);
-		raw_spin_unlock(&buf->raw_tick_nohz_spinlock);
-		break;
-	case TICK_NOHZ_STOP:
-		spin_lock(&__get_cpu_var(ring_buffer_nohz_lock));
-		lib_ring_buffer_stop_switch_timer(buf);
-		lib_ring_buffer_stop_read_timer(buf);
-		spin_unlock(&__get_cpu_var(ring_buffer_nohz_lock));
-		break;
-	case TICK_NOHZ_RESTART:
-		spin_lock(&__get_cpu_var(ring_buffer_nohz_lock));
-		lib_ring_buffer_start_read_timer(buf);
-		lib_ring_buffer_start_switch_timer(buf);
-		spin_unlock(&__get_cpu_var(ring_buffer_nohz_lock));
-		break;
-	}
-
-	return 0;
-}
-
-void notrace lib_ring_buffer_tick_nohz_flush(void)
-{
-	atomic_notifier_call_chain(&tick_nohz_notifier, TICK_NOHZ_FLUSH,
-				   NULL);
-}
-
-void notrace lib_ring_buffer_tick_nohz_stop(void)
-{
-	atomic_notifier_call_chain(&tick_nohz_notifier, TICK_NOHZ_STOP,
-				   NULL);
-}
-
-void notrace lib_ring_buffer_tick_nohz_restart(void)
-{
-	atomic_notifier_call_chain(&tick_nohz_notifier, TICK_NOHZ_RESTART,
-				   NULL);
-}
-#endif /* defined(CONFIG_NO_HZ) && defined(CONFIG_LIB_RING_BUFFER) */
-
-/*
- * Holds CPU hotplug.
- */
-static void channel_unregister_notifiers(struct channel *chan)
+static void channel_unregister_notifiers(struct channel *chan,
+			   struct lttng_ust_shm_handle *handle)
 {
-	const struct lib_ring_buffer_config *config = chan->backend.config;
+	const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
 	int cpu;
 
-	channel_iterator_unregister_notifiers(chan);
 	if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
-#ifdef CONFIG_NO_HZ
-		/*
-		 * Remove the nohz notifier first, so we are certain we stop
-		 * the timers.
-		 */
-		atomic_notifier_chain_unregister(&tick_nohz_notifier,
-						 &chan->tick_nohz_notifier);
-		/*
-		 * ring_buffer_nohz_lock will not be needed below, because
-		 * we just removed the notifiers, which were the only source of
-		 * concurrency.
-		 */
-#endif /* CONFIG_NO_HZ */
-#ifdef CONFIG_HOTPLUG_CPU
-		get_online_cpus();
-		chan->cpu_hp_enable = 0;
-		for_each_online_cpu(cpu) {
-			struct lib_ring_buffer *buf = per_cpu_ptr(chan->backend.buf,
-							      cpu);
-			lib_ring_buffer_stop_switch_timer(buf);
-			lib_ring_buffer_stop_read_timer(buf);
-		}
-		put_online_cpus();
-		unregister_cpu_notifier(&chan->cpu_hp_notifier);
-#else
 		for_each_possible_cpu(cpu) {
-			struct lib_ring_buffer *buf = per_cpu_ptr(chan->backend.buf,
-							      cpu);
-			lib_ring_buffer_stop_switch_timer(buf);
-			lib_ring_buffer_stop_read_timer(buf);
+			struct lttng_ust_lib_ring_buffer *buf = shmp(handle, chan->backend.buf[cpu].shmp);
+
+			lib_ring_buffer_stop_switch_timer(buf, handle);
+			lib_ring_buffer_stop_read_timer(buf, handle);
 		}
-#endif
 	} else {
-		struct lib_ring_buffer *buf = chan->backend.buf;
+		struct lttng_ust_lib_ring_buffer *buf = shmp(handle, chan->backend.buf[0].shmp);
 
-		lib_ring_buffer_stop_switch_timer(buf);
-		lib_ring_buffer_stop_read_timer(buf);
+		lib_ring_buffer_stop_switch_timer(buf, handle);
+		lib_ring_buffer_stop_read_timer(buf, handle);
 	}
-	channel_backend_unregister_notifiers(&chan->backend);
+	//channel_backend_unregister_notifiers(&chan->backend);
 }
 
-static void channel_free(struct channel *chan)
+static void channel_free(struct channel *chan, struct lttng_ust_shm_handle *handle,
+		int shadow)
 {
-	channel_iterator_free(chan);
-	channel_backend_free(&chan->backend);
-	kfree(chan);
+	if (!shadow)
+		channel_backend_free(&chan->backend, handle);
+	/* chan is freed by shm teardown */
+	shm_object_table_destroy(handle->table);
+	free(handle);
 }
 
 /**
  * channel_create - Create channel.
  * @config: ring buffer instance configuration
  * @name: name of the channel
- * @priv: ring buffer client private data
+ * @priv_data: ring buffer client private data area pointer (output)
+ * @priv_data_size: length, in bytes, of the private data area.
+ * @priv_data_init: initialization data for private data.
  * @buf_addr: pointer the the beginning of the preallocated buffer contiguous
  *            address mapping. It is used only by RING_BUFFER_STATIC
  *            configuration. It can be set to NULL for other backends.
@@ -596,103 +430,166 @@ static void channel_free(struct channel *chan)
  * Holds cpu hotplug.
  * Returns NULL on failure.
  */
-struct channel *channel_create(const struct lib_ring_buffer_config *config,
-		   const char *name, void *priv, void *buf_addr,
-		   size_t subbuf_size,
+struct lttng_ust_shm_handle *channel_create(const struct lttng_ust_lib_ring_buffer_config *config,
+		   const char *name,
+		   void **priv_data,
+		   size_t priv_data_align,
+		   size_t priv_data_size,
+		   void *priv_data_init,
+		   void *buf_addr, size_t subbuf_size,
 		   size_t num_subbuf, unsigned int switch_timer_interval,
-		   unsigned int read_timer_interval)
+		   unsigned int read_timer_interval,
+		   int **shm_fd, int **wait_fd, uint64_t **memory_map_size)
 {
 	int ret, cpu;
+	size_t shmsize, chansize;
 	struct channel *chan;
+	struct lttng_ust_shm_handle *handle;
+	struct shm_object *shmobj;
+	struct shm_ref *ref;
 
 	if (lib_ring_buffer_check_config(config, switch_timer_interval,
 					 read_timer_interval))
 		return NULL;
 
-	chan = kzalloc(sizeof(struct channel), GFP_KERNEL);
-	if (!chan)
+	handle = zmalloc(sizeof(struct lttng_ust_shm_handle));
+	if (!handle)
 		return NULL;
 
-	ret = channel_backend_init(&chan->backend, name, config, priv,
-				   subbuf_size, num_subbuf);
-	if (ret)
-		goto error;
+	/* Allocate table for channel + per-cpu buffers */
+	handle->table = shm_object_table_create(1 + num_possible_cpus());
+	if (!handle->table)
+		goto error_table_alloc;
+
+	/* Calculate the shm allocation layout */
+	shmsize = sizeof(struct channel);
+	shmsize += offset_align(shmsize, __alignof__(struct lttng_ust_lib_ring_buffer_shmp));
+	if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
+		shmsize += sizeof(struct lttng_ust_lib_ring_buffer_shmp) * num_possible_cpus();
+	else
+		shmsize += sizeof(struct lttng_ust_lib_ring_buffer_shmp);
+	chansize = shmsize;
+	shmsize += offset_align(shmsize, priv_data_align);
+	shmsize += priv_data_size;
+
+	shmobj = shm_object_table_append(handle->table, shmsize);
+	if (!shmobj)
+		goto error_append;
+	/* struct channel is at object 0, offset 0 (hardcoded) */
+	set_shmp(handle->chan, zalloc_shm(shmobj, chansize));
+	assert(handle->chan._ref.index == 0);
+	assert(handle->chan._ref.offset == 0);
+	chan = shmp(handle, handle->chan);
+	if (!chan)
+		goto error_append;
+
+	/* space for private data */
+	if (priv_data_size) {
+		DECLARE_SHMP(void, priv_data_alloc);
+
+		align_shm(shmobj, priv_data_align);
+		chan->priv_data_offset = shmobj->allocated_len;
+		set_shmp(priv_data_alloc, zalloc_shm(shmobj, priv_data_size));
+		if (!shmp(handle, priv_data_alloc))
+			goto error_append;
+		*priv_data = channel_get_private(chan);
+		memcpy(*priv_data, priv_data_init, priv_data_size);
+	} else {
+		chan->priv_data_offset = -1;
+		*priv_data = NULL;
+	}
 
-	ret = channel_iterator_init(chan);
+	ret = channel_backend_init(&chan->backend, name, config,
+				   subbuf_size, num_subbuf, handle);
 	if (ret)
-		goto error_free_backend;
+		goto error_backend_init;
 
 	chan->commit_count_mask = (~0UL >> chan->backend.num_subbuf_order);
-	chan->switch_timer_interval = usecs_to_jiffies(switch_timer_interval);
-	chan->read_timer_interval = usecs_to_jiffies(read_timer_interval);
-	kref_init(&chan->ref);
-	init_waitqueue_head(&chan->read_wait);
-	init_waitqueue_head(&chan->hp_wait);
+	//TODO
+	//chan->switch_timer_interval = usecs_to_jiffies(switch_timer_interval);
+	//chan->read_timer_interval = usecs_to_jiffies(read_timer_interval);
+	//TODO
+	//init_waitqueue_head(&chan->read_wait);
+	//init_waitqueue_head(&chan->hp_wait);
 
 	if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
-#if defined(CONFIG_NO_HZ) && defined(CONFIG_LIB_RING_BUFFER)
-		/* Only benefit from NO_HZ idle with per-cpu buffers for now. */
-		chan->tick_nohz_notifier.notifier_call =
-			ring_buffer_tick_nohz_callback;
-		chan->tick_nohz_notifier.priority = ~0U;
-		atomic_notifier_chain_register(&tick_nohz_notifier,
-				       &chan->tick_nohz_notifier);
-#endif /* defined(CONFIG_NO_HZ) && defined(CONFIG_LIB_RING_BUFFER) */
-
 		/*
 		 * In case of non-hotplug cpu, if the ring-buffer is allocated
 		 * in early initcall, it will not be notified of secondary cpus.
 		 * In that off case, we need to allocate for all possible cpus.
 		 */
-#ifdef CONFIG_HOTPLUG_CPU
-		chan->cpu_hp_notifier.notifier_call =
-				lib_ring_buffer_cpu_hp_callback;
-		chan->cpu_hp_notifier.priority = 6;
-		register_cpu_notifier(&chan->cpu_hp_notifier);
-
-		get_online_cpus();
-		for_each_online_cpu(cpu) {
-			struct lib_ring_buffer *buf = per_cpu_ptr(chan->backend.buf,
-							       cpu);
-			spin_lock(&per_cpu(ring_buffer_nohz_lock, cpu));
-			lib_ring_buffer_start_switch_timer(buf);
-			lib_ring_buffer_start_read_timer(buf);
-			spin_unlock(&per_cpu(ring_buffer_nohz_lock, cpu));
-		}
-		chan->cpu_hp_enable = 1;
-		put_online_cpus();
-#else
 		for_each_possible_cpu(cpu) {
-			struct lib_ring_buffer *buf = per_cpu_ptr(chan->backend.buf,
-							      cpu);
-			spin_lock(&per_cpu(ring_buffer_nohz_lock, cpu));
-			lib_ring_buffer_start_switch_timer(buf);
-			lib_ring_buffer_start_read_timer(buf);
-			spin_unlock(&per_cpu(ring_buffer_nohz_lock, cpu));
+			struct lttng_ust_lib_ring_buffer *buf = shmp(handle, chan->backend.buf[cpu].shmp);
+			lib_ring_buffer_start_switch_timer(buf, handle);
+			lib_ring_buffer_start_read_timer(buf, handle);
 		}
-#endif
 	} else {
-		struct lib_ring_buffer *buf = chan->backend.buf;
+		struct lttng_ust_lib_ring_buffer *buf = shmp(handle, chan->backend.buf[0].shmp);
 
-		lib_ring_buffer_start_switch_timer(buf);
-		lib_ring_buffer_start_read_timer(buf);
+		lib_ring_buffer_start_switch_timer(buf, handle);
+		lib_ring_buffer_start_read_timer(buf, handle);
 	}
+	ref = &handle->chan._ref;
+	shm_get_object_data(handle, ref, shm_fd, wait_fd, memory_map_size);
+	return handle;
+
+error_backend_init:
+error_append:
+	shm_object_table_destroy(handle->table);
+error_table_alloc:
+	free(handle);
+	return NULL;
+}
+
+struct lttng_ust_shm_handle *channel_handle_create(int shm_fd, int wait_fd,
+					uint64_t memory_map_size)
+{
+	struct lttng_ust_shm_handle *handle;
+	struct shm_object *object;
 
-	return chan;
+	handle = zmalloc(sizeof(struct lttng_ust_shm_handle));
+	if (!handle)
+		return NULL;
 
-error_free_backend:
-	channel_backend_free(&chan->backend);
-error:
-	kfree(chan);
+	/* Allocate table for channel + per-cpu buffers */
+	handle->table = shm_object_table_create(1 + num_possible_cpus());
+	if (!handle->table)
+		goto error_table_alloc;
+	/* Add channel object */
+	object = shm_object_table_append_shadow(handle->table,
+			shm_fd, wait_fd, memory_map_size);
+	if (!object)
+		goto error_table_object;
+	/* struct channel is at object 0, offset 0 (hardcoded) */
+	handle->chan._ref.index = 0;
+	handle->chan._ref.offset = 0;
+	return handle;
+
+error_table_object:
+	shm_object_table_destroy(handle->table);
+error_table_alloc:
+	free(handle);
 	return NULL;
 }
-EXPORT_SYMBOL_GPL(channel_create);
+
+int channel_handle_add_stream(struct lttng_ust_shm_handle *handle,
+		int shm_fd, int wait_fd, uint64_t memory_map_size)
+{
+	struct shm_object *object;
+
+	/* Add stream object */
+	object = shm_object_table_append_shadow(handle->table,
+			shm_fd, wait_fd, memory_map_size);
+	if (!object)
+		return -1;
+	return 0;
+}
 
 static
-void channel_release(struct kref *kref)
+void channel_release(struct channel *chan, struct lttng_ust_shm_handle *handle,
+		int shadow)
 {
-	struct channel *chan = container_of(kref, struct channel, ref);
-	channel_free(chan);
+	channel_free(chan, handle, shadow);
 }
 
 /**
@@ -700,108 +597,89 @@ void channel_release(struct kref *kref)
  * @chan: channel to destroy
  *
  * Holds cpu hotplug.
- * Call "destroy" callback, finalize channels, wait for readers to release their
- * reference, then destroy ring buffer data. Note that when readers have
- * completed data consumption of finalized channels, get_subbuf() will return
- * -ENODATA. They should release their handle at that point.
- * Returns the private data pointer.
+ * Call "destroy" callback, finalize channels, decrement the channel
+ * reference count. Note that when readers have completed data
+ * consumption of finalized channels, get_subbuf() will return -ENODATA.
+ * They should release their handle at that point. 
  */
-void *channel_destroy(struct channel *chan)
+void channel_destroy(struct channel *chan, struct lttng_ust_shm_handle *handle,
+		int shadow)
 {
-	int cpu;
-	const struct lib_ring_buffer_config *config = chan->backend.config;
-	void *priv;
+	if (shadow) {
+		channel_release(chan, handle, shadow);
+		return;
+	}
 
-	channel_unregister_notifiers(chan);
+	channel_unregister_notifiers(chan, handle);
 
-	if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
-		/*
-		 * No need to hold cpu hotplug, because all notifiers have been
-		 * unregistered.
-		 */
-		for_each_channel_cpu(cpu, chan) {
-			struct lib_ring_buffer *buf = per_cpu_ptr(chan->backend.buf,
-							      cpu);
-
-			if (config->cb.buffer_finalize)
-				config->cb.buffer_finalize(buf,
-							   chan->backend.priv,
-							   cpu);
-			if (buf->backend.allocated)
-				lib_ring_buffer_switch_slow(buf, SWITCH_FLUSH);
-			/*
-			 * Perform flush before writing to finalized.
-			 */
-			smp_wmb();
-			ACCESS_ONCE(buf->finalized) = 1;
-			wake_up_interruptible(&buf->read_wait);
-		}
-	} else {
-		struct lib_ring_buffer *buf = chan->backend.buf;
+	/*
+	 * Note: the consumer takes care of finalizing and switching the
+	 * buffers.
+	 */
 
-		if (config->cb.buffer_finalize)
-			config->cb.buffer_finalize(buf, chan->backend.priv, -1);
-		if (buf->backend.allocated)
-			lib_ring_buffer_switch_slow(buf, SWITCH_FLUSH);
-		/*
-		 * Perform flush before writing to finalized.
-		 */
-		smp_wmb();
-		ACCESS_ONCE(buf->finalized) = 1;
-		wake_up_interruptible(&buf->read_wait);
-	}
-	ACCESS_ONCE(chan->finalized) = 1;
-	wake_up_interruptible(&chan->hp_wait);
-	wake_up_interruptible(&chan->read_wait);
-	kref_put(&chan->ref, channel_release);
-	priv = chan->backend.priv;
-	return priv;
+	/*
+	 * sessiond/consumer are keeping a reference on the shm file
+	 * descriptor directly. No need to refcount.
+	 */
+	channel_release(chan, handle, shadow);
+	return;
 }
-EXPORT_SYMBOL_GPL(channel_destroy);
 
-struct lib_ring_buffer *channel_get_ring_buffer(
-					const struct lib_ring_buffer_config *config,
-					struct channel *chan, int cpu)
+struct lttng_ust_lib_ring_buffer *channel_get_ring_buffer(
+					const struct lttng_ust_lib_ring_buffer_config *config,
+					struct channel *chan, int cpu,
+					struct lttng_ust_shm_handle *handle,
+					int **shm_fd, int **wait_fd,
+					uint64_t **memory_map_size)
 {
-	if (config->alloc == RING_BUFFER_ALLOC_GLOBAL)
-		return chan->backend.buf;
-	else
-		return per_cpu_ptr(chan->backend.buf, cpu);
+	struct shm_ref *ref;
+
+	if (config->alloc == RING_BUFFER_ALLOC_GLOBAL) {
+		ref = &chan->backend.buf[0].shmp._ref;
+		shm_get_object_data(handle, ref, shm_fd, wait_fd,
+			memory_map_size);
+		return shmp(handle, chan->backend.buf[0].shmp);
+	} else {
+		if (cpu >= num_possible_cpus())
+			return NULL;
+		ref = &chan->backend.buf[cpu].shmp._ref;
+		shm_get_object_data(handle, ref, shm_fd, wait_fd,
+			memory_map_size);
+		return shmp(handle, chan->backend.buf[cpu].shmp);
+	}
 }
-EXPORT_SYMBOL_GPL(channel_get_ring_buffer);
 
-int lib_ring_buffer_open_read(struct lib_ring_buffer *buf)
+int lib_ring_buffer_open_read(struct lttng_ust_lib_ring_buffer *buf,
+			      struct lttng_ust_shm_handle *handle,
+			      int shadow)
 {
-	struct channel *chan = buf->backend.chan;
-
-	if (!atomic_long_add_unless(&buf->active_readers, 1, 1))
+	if (shadow) {
+		if (uatomic_cmpxchg(&buf->active_shadow_readers, 0, 1) != 0)
+			return -EBUSY;
+		cmm_smp_mb();
+		return 0;
+	}
+	if (uatomic_cmpxchg(&buf->active_readers, 0, 1) != 0)
 		return -EBUSY;
-	kref_get(&chan->ref);
-	smp_mb__after_atomic_inc();
+	cmm_smp_mb();
 	return 0;
 }
-EXPORT_SYMBOL_GPL(lib_ring_buffer_open_read);
 
-void lib_ring_buffer_release_read(struct lib_ring_buffer *buf)
+void lib_ring_buffer_release_read(struct lttng_ust_lib_ring_buffer *buf,
+				  struct lttng_ust_shm_handle *handle,
+				  int shadow)
 {
-	struct channel *chan = buf->backend.chan;
-
-	CHAN_WARN_ON(chan, atomic_long_read(&buf->active_readers) != 1);
-	smp_mb__before_atomic_dec();
-	atomic_long_dec(&buf->active_readers);
-	kref_put(&chan->ref, channel_release);
-}
-EXPORT_SYMBOL_GPL(lib_ring_buffer_release_read);
+	struct channel *chan = shmp(handle, buf->backend.chan);
 
-/*
- * Promote compiler barrier to a smp_mb().
- * For the specific ring buffer case, this IPI call should be removed if the
- * architecture does not reorder writes.  This should eventually be provided by
- * a separate architecture-specific infrastructure.
- */
-static void remote_mb(void *info)
-{
-	smp_mb();
+	if (shadow) {
+		CHAN_WARN_ON(chan, uatomic_read(&buf->active_shadow_readers) != 1);
+		cmm_smp_mb();
+		uatomic_dec(&buf->active_shadow_readers);
+		return;
+	}
+	CHAN_WARN_ON(chan, uatomic_read(&buf->active_readers) != 1);
+	cmm_smp_mb();
+	uatomic_dec(&buf->active_readers);
 }
 
 /**
@@ -812,24 +690,23 @@ static void remote_mb(void *info)
  *
  * Returns -ENODATA if buffer is finalized, -EAGAIN if there is currently no
  * data to read at consumed position, or 0 if the get operation succeeds.
- * Busy-loop trying to get data if the tick_nohz sequence lock is held.
  */
 
-int lib_ring_buffer_snapshot(struct lib_ring_buffer *buf,
-			     unsigned long *consumed, unsigned long *produced)
+int lib_ring_buffer_snapshot(struct lttng_ust_lib_ring_buffer *buf,
+			     unsigned long *consumed, unsigned long *produced,
+			     struct lttng_ust_shm_handle *handle)
 {
-	struct channel *chan = buf->backend.chan;
-	const struct lib_ring_buffer_config *config = chan->backend.config;
+	struct channel *chan = shmp(handle, buf->backend.chan);
+	const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
 	unsigned long consumed_cur, write_offset;
 	int finalized;
 
-retry:
-	finalized = ACCESS_ONCE(buf->finalized);
+	finalized = CMM_ACCESS_ONCE(buf->finalized);
 	/*
 	 * Read finalized before counters.
 	 */
-	smp_rmb();
-	consumed_cur = atomic_long_read(&buf->consumed);
+	cmm_smp_rmb();
+	consumed_cur = uatomic_read(&buf->consumed);
 	/*
 	 * No need to issue a memory barrier between consumed count read and
 	 * write offset read, because consumed count can only change
@@ -860,38 +737,36 @@ nodata:
 	 */
 	if (finalized)
 		return -ENODATA;
-	else if (raw_spin_is_locked(&buf->raw_tick_nohz_spinlock))
-		goto retry;
 	else
 		return -EAGAIN;
 }
-EXPORT_SYMBOL_GPL(lib_ring_buffer_snapshot);
 
 /**
  * lib_ring_buffer_put_snapshot - move consumed counter forward
  * @buf: ring buffer
  * @consumed_new: new consumed count value
  */
-void lib_ring_buffer_move_consumer(struct lib_ring_buffer *buf,
-				   unsigned long consumed_new)
+void lib_ring_buffer_move_consumer(struct lttng_ust_lib_ring_buffer *buf,
+				   unsigned long consumed_new,
+				   struct lttng_ust_shm_handle *handle)
 {
-	struct lib_ring_buffer_backend *bufb = &buf->backend;
-	struct channel *chan = bufb->chan;
+	struct lttng_ust_lib_ring_buffer_backend *bufb = &buf->backend;
+	struct channel *chan = shmp(handle, bufb->chan);
 	unsigned long consumed;
 
-	CHAN_WARN_ON(chan, atomic_long_read(&buf->active_readers) != 1);
+	CHAN_WARN_ON(chan, uatomic_read(&buf->active_readers) != 1
+			&& uatomic_read(&buf->active_shadow_readers) != 1);
 
 	/*
 	 * Only push the consumed value forward.
 	 * If the consumed cmpxchg fails, this is because we have been pushed by
 	 * the writer in flight recorder mode.
 	 */
-	consumed = atomic_long_read(&buf->consumed);
+	consumed = uatomic_read(&buf->consumed);
 	while ((long) consumed - (long) consumed_new < 0)
-		consumed = atomic_long_cmpxchg(&buf->consumed, consumed,
-					       consumed_new);
+		consumed = uatomic_cmpxchg(&buf->consumed, consumed,
+					   consumed_new);
 }
-EXPORT_SYMBOL_GPL(lib_ring_buffer_move_consumer);
 
 /**
  * lib_ring_buffer_get_subbuf - get exclusive access to subbuffer for reading
@@ -900,88 +775,37 @@ EXPORT_SYMBOL_GPL(lib_ring_buffer_move_consumer);
  *
  * Returns -ENODATA if buffer is finalized, -EAGAIN if there is currently no
  * data to read at consumed position, or 0 if the get operation succeeds.
- * Busy-loop trying to get data if the tick_nohz sequence lock is held.
  */
-int lib_ring_buffer_get_subbuf(struct lib_ring_buffer *buf,
-			       unsigned long consumed)
+int lib_ring_buffer_get_subbuf(struct lttng_ust_lib_ring_buffer *buf,
+			       unsigned long consumed,
+			       struct lttng_ust_shm_handle *handle)
 {
-	struct channel *chan = buf->backend.chan;
-	const struct lib_ring_buffer_config *config = chan->backend.config;
+	struct channel *chan = shmp(handle, buf->backend.chan);
+	const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
 	unsigned long consumed_cur, consumed_idx, commit_count, write_offset;
 	int ret;
 	int finalized;
 
 retry:
-	finalized = ACCESS_ONCE(buf->finalized);
+	finalized = CMM_ACCESS_ONCE(buf->finalized);
 	/*
 	 * Read finalized before counters.
 	 */
-	smp_rmb();
-	consumed_cur = atomic_long_read(&buf->consumed);
+	cmm_smp_rmb();
+	consumed_cur = uatomic_read(&buf->consumed);
 	consumed_idx = subbuf_index(consumed, chan);
-	commit_count = v_read(config, &buf->commit_cold[consumed_idx].cc_sb);
+	commit_count = v_read(config, &shmp_index(handle, buf->commit_cold, consumed_idx)->cc_sb);
 	/*
 	 * Make sure we read the commit count before reading the buffer
 	 * data and the write offset. Correct consumed offset ordering
 	 * wrt commit count is insured by the use of cmpxchg to update
 	 * the consumed offset.
-	 * smp_call_function_single can fail if the remote CPU is offline,
-	 * this is OK because then there is no wmb to execute there.
-	 * If our thread is executing on the same CPU as the on the buffers
-	 * belongs to, we don't have to synchronize it at all. If we are
-	 * migrated, the scheduler will take care of the memory barriers.
-	 * Normally, smp_call_function_single() should ensure program order when
-	 * executing the remote function, which implies that it surrounds the
-	 * function execution with :
-	 * smp_mb()
-	 * send IPI
-	 * csd_lock_wait
-	 *                recv IPI
-	 *                smp_mb()
-	 *                exec. function
-	 *                smp_mb()
-	 *                csd unlock
-	 * smp_mb()
-	 *
-	 * However, smp_call_function_single() does not seem to clearly execute
-	 * such barriers. It depends on spinlock semantic to provide the barrier
-	 * before executing the IPI and, when busy-looping, csd_lock_wait only
-	 * executes smp_mb() when it has to wait for the other CPU.
-	 *
-	 * I don't trust this code. Therefore, let's add the smp_mb() sequence
-	 * required ourself, even if duplicated. It has no performance impact
-	 * anyway.
-	 *
-	 * smp_mb() is needed because smp_rmb() and smp_wmb() only order read vs
-	 * read and write vs write. They do not ensure core synchronization. We
-	 * really have to ensure total order between the 3 barriers running on
-	 * the 2 CPUs.
 	 */
-	if (config->ipi == RING_BUFFER_IPI_BARRIER) {
-		if (config->sync == RING_BUFFER_SYNC_PER_CPU
-		    && config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
-			if (raw_smp_processor_id() != buf->backend.cpu) {
-				/* Total order with IPI handler smp_mb() */
-				smp_mb();
-				smp_call_function_single(buf->backend.cpu,
-							 remote_mb, NULL, 1);
-				/* Total order with IPI handler smp_mb() */
-				smp_mb();
-			}
-		} else {
-			/* Total order with IPI handler smp_mb() */
-			smp_mb();
-			smp_call_function(remote_mb, NULL, 1);
-			/* Total order with IPI handler smp_mb() */
-			smp_mb();
-		}
-	} else {
-		/*
-		 * Local rmb to match the remote wmb to read the commit count
-		 * before the buffer data and the write offset.
-		 */
-		smp_rmb();
-	}
+	/*
+	 * Local rmb to match the remote wmb to read the commit count
+	 * before the buffer data and the write offset.
+	 */
+	cmm_smp_rmb();
 
 	write_offset = v_read(config, &buf->offset);
 
@@ -1020,7 +844,8 @@ retry:
 	 * looking for matches the one contained in the subbuffer id.
 	 */
 	ret = update_read_sb_index(config, &buf->backend, &chan->backend,
-				   consumed_idx, buf_trunc_val(consumed, chan));
+				   consumed_idx, buf_trunc_val(consumed, chan),
+				   handle);
 	if (ret)
 		goto retry;
 	subbuffer_id_clear_noref(config, &buf->backend.buf_rsb.id);
@@ -1037,25 +862,24 @@ nodata:
 	 */
 	if (finalized)
 		return -ENODATA;
-	else if (raw_spin_is_locked(&buf->raw_tick_nohz_spinlock))
-		goto retry;
 	else
 		return -EAGAIN;
 }
-EXPORT_SYMBOL_GPL(lib_ring_buffer_get_subbuf);
 
 /**
  * lib_ring_buffer_put_subbuf - release exclusive subbuffer access
  * @buf: ring buffer
  */
-void lib_ring_buffer_put_subbuf(struct lib_ring_buffer *buf)
+void lib_ring_buffer_put_subbuf(struct lttng_ust_lib_ring_buffer *buf,
+				struct lttng_ust_shm_handle *handle)
 {
-	struct lib_ring_buffer_backend *bufb = &buf->backend;
-	struct channel *chan = bufb->chan;
-	const struct lib_ring_buffer_config *config = chan->backend.config;
+	struct lttng_ust_lib_ring_buffer_backend *bufb = &buf->backend;
+	struct channel *chan = shmp(handle, bufb->chan);
+	const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
 	unsigned long read_sb_bindex, consumed_idx, consumed;
 
-	CHAN_WARN_ON(chan, atomic_long_read(&buf->active_readers) != 1);
+	CHAN_WARN_ON(chan, uatomic_read(&buf->active_readers) != 1
+			&& uatomic_read(&buf->active_shadow_readers) != 1);
 
 	if (!buf->get_subbuf) {
 		/*
@@ -1076,9 +900,9 @@ void lib_ring_buffer_put_subbuf(struct lib_ring_buffer *buf)
 	 */
 	read_sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id);
 	v_add(config, v_read(config,
-			     &bufb->array[read_sb_bindex]->records_unread),
+			     &shmp(handle, shmp_index(handle, bufb->array, read_sb_bindex)->shmp)->records_unread),
 	      &bufb->records_read);
-	v_set(config, &bufb->array[read_sb_bindex]->records_unread, 0);
+	v_set(config, &shmp(handle, shmp_index(handle, bufb->array, read_sb_bindex)->shmp)->records_unread, 0);
 	CHAN_WARN_ON(chan, config->mode == RING_BUFFER_OVERWRITE
 		     && subbuffer_id_is_noref(config, bufb->buf_rsb.id));
 	subbuffer_id_set_noref(config, &bufb->buf_rsb.id);
@@ -1093,34 +917,34 @@ void lib_ring_buffer_put_subbuf(struct lib_ring_buffer *buf)
 	 */
 	consumed_idx = subbuf_index(consumed, chan);
 	update_read_sb_index(config, &buf->backend, &chan->backend,
-			     consumed_idx, buf_trunc_val(consumed, chan));
+			     consumed_idx, buf_trunc_val(consumed, chan),
+			     handle);
 	/*
 	 * update_read_sb_index return value ignored. Don't exchange sub-buffer
 	 * if the writer concurrently updated it.
 	 */
 }
-EXPORT_SYMBOL_GPL(lib_ring_buffer_put_subbuf);
 
 /*
  * cons_offset is an iterator on all subbuffer offsets between the reader
  * position and the writer position. (inclusive)
  */
 static
-void lib_ring_buffer_print_subbuffer_errors(struct lib_ring_buffer *buf,
+void lib_ring_buffer_print_subbuffer_errors(struct lttng_ust_lib_ring_buffer *buf,
 					    struct channel *chan,
 					    unsigned long cons_offset,
-					    int cpu)
+					    int cpu,
+					    struct lttng_ust_shm_handle *handle)
 {
-	const struct lib_ring_buffer_config *config = chan->backend.config;
+	const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
 	unsigned long cons_idx, commit_count, commit_count_sb;
 
 	cons_idx = subbuf_index(cons_offset, chan);
-	commit_count = v_read(config, &buf->commit_hot[cons_idx].cc);
-	commit_count_sb = v_read(config, &buf->commit_cold[cons_idx].cc_sb);
+	commit_count = v_read(config, &shmp_index(handle, buf->commit_hot, cons_idx)->cc);
+	commit_count_sb = v_read(config, &shmp_index(handle, buf->commit_cold, cons_idx)->cc_sb);
 
 	if (subbuf_offset(commit_count, chan) != 0)
-		printk(KERN_WARNING
-		       "ring buffer %s, cpu %d: "
+		DBG("ring buffer %s, cpu %d: "
 		       "commit count in subbuffer %lu,\n"
 		       "expecting multiples of %lu bytes\n"
 		       "  [ %lu bytes committed, %lu bytes reader-visible ]\n",
@@ -1128,73 +952,74 @@ void lib_ring_buffer_print_subbuffer_errors(struct lib_ring_buffer *buf,
 		       chan->backend.subbuf_size,
 		       commit_count, commit_count_sb);
 
-	printk(KERN_DEBUG "ring buffer: %s, cpu %d: %lu bytes committed\n",
+	DBG("ring buffer: %s, cpu %d: %lu bytes committed\n",
 	       chan->backend.name, cpu, commit_count);
 }
 
 static
-void lib_ring_buffer_print_buffer_errors(struct lib_ring_buffer *buf,
+void lib_ring_buffer_print_buffer_errors(struct lttng_ust_lib_ring_buffer *buf,
 					 struct channel *chan,
-					 void *priv, int cpu)
+					 void *priv, int cpu,
+					 struct lttng_ust_shm_handle *handle)
 {
-	const struct lib_ring_buffer_config *config = chan->backend.config;
+	const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
 	unsigned long write_offset, cons_offset;
 
-	/*
-	 * Can be called in the error path of allocation when
-	 * trans_channel_data is not yet set.
-	 */
-	if (!chan)
-		return;
 	/*
 	 * No need to order commit_count, write_offset and cons_offset reads
 	 * because we execute at teardown when no more writer nor reader
 	 * references are left.
 	 */
 	write_offset = v_read(config, &buf->offset);
-	cons_offset = atomic_long_read(&buf->consumed);
+	cons_offset = uatomic_read(&buf->consumed);
 	if (write_offset != cons_offset)
-		printk(KERN_WARNING
-		       "ring buffer %s, cpu %d: "
+		DBG("ring buffer %s, cpu %d: "
 		       "non-consumed data\n"
 		       "  [ %lu bytes written, %lu bytes read ]\n",
 		       chan->backend.name, cpu, write_offset, cons_offset);
 
-	for (cons_offset = atomic_long_read(&buf->consumed);
+	for (cons_offset = uatomic_read(&buf->consumed);
 	     (long) (subbuf_trunc((unsigned long) v_read(config, &buf->offset),
 				  chan)
 		     - cons_offset) > 0;
 	     cons_offset = subbuf_align(cons_offset, chan))
 		lib_ring_buffer_print_subbuffer_errors(buf, chan, cons_offset,
-						       cpu);
+						       cpu, handle);
 }
 
 static
 void lib_ring_buffer_print_errors(struct channel *chan,
-				  struct lib_ring_buffer *buf, int cpu)
+				  struct lttng_ust_lib_ring_buffer *buf, int cpu,
+				  struct lttng_ust_shm_handle *handle)
 {
-	const struct lib_ring_buffer_config *config = chan->backend.config;
-	void *priv = chan->backend.priv;
-
-	printk(KERN_DEBUG "ring buffer %s, cpu %d: %lu records written, "
-			  "%lu records overrun\n",
-			  chan->backend.name, cpu,
-			  v_read(config, &buf->records_count),
-			  v_read(config, &buf->records_overrun));
-
-	if (v_read(config, &buf->records_lost_full)
-	    || v_read(config, &buf->records_lost_wrap)
-	    || v_read(config, &buf->records_lost_big))
-		printk(KERN_WARNING
-		       "ring buffer %s, cpu %d: records were lost. Caused by:\n"
-		       "  [ %lu buffer full, %lu nest buffer wrap-around, "
-		       "%lu event too big ]\n",
-		       chan->backend.name, cpu,
-		       v_read(config, &buf->records_lost_full),
-		       v_read(config, &buf->records_lost_wrap),
-		       v_read(config, &buf->records_lost_big));
-
-	lib_ring_buffer_print_buffer_errors(buf, chan, priv, cpu);
+	const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
+	void *priv = channel_get_private(chan);
+
+	if (!strcmp(chan->backend.name, "relay-metadata-mmap")) {
+		DBG("ring buffer %s: %lu records written, "
+			"%lu records overrun\n",
+			chan->backend.name,
+			v_read(config, &buf->records_count),
+			v_read(config, &buf->records_overrun));
+	} else {
+		DBG("ring buffer %s, cpu %d: %lu records written, "
+			"%lu records overrun\n",
+			chan->backend.name, cpu,
+			v_read(config, &buf->records_count),
+			v_read(config, &buf->records_overrun));
+
+		if (v_read(config, &buf->records_lost_full)
+		    || v_read(config, &buf->records_lost_wrap)
+		    || v_read(config, &buf->records_lost_big))
+			DBG("ring buffer %s, cpu %d: records were lost. Caused by:\n"
+				"  [ %lu buffer full, %lu nest buffer wrap-around, "
+				"%lu event too big ]\n",
+				chan->backend.name, cpu,
+				v_read(config, &buf->records_lost_full),
+				v_read(config, &buf->records_lost_wrap),
+				v_read(config, &buf->records_lost_big));
+	}
+	lib_ring_buffer_print_buffer_errors(buf, chan, priv, cpu, handle);
 }
 
 /*
@@ -1203,39 +1028,33 @@ void lib_ring_buffer_print_errors(struct channel *chan,
  * Only executed when the buffer is finalized, in SWITCH_FLUSH.
  */
 static
-void lib_ring_buffer_switch_old_start(struct lib_ring_buffer *buf,
+void lib_ring_buffer_switch_old_start(struct lttng_ust_lib_ring_buffer *buf,
 				      struct channel *chan,
 				      struct switch_offsets *offsets,
-				      u64 tsc)
+				      uint64_t tsc,
+				      struct lttng_ust_shm_handle *handle)
 {
-	const struct lib_ring_buffer_config *config = chan->backend.config;
+	const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
 	unsigned long oldidx = subbuf_index(offsets->old, chan);
 	unsigned long commit_count;
 
-	config->cb.buffer_begin(buf, tsc, oldidx);
+	config->cb.buffer_begin(buf, tsc, oldidx, handle);
 
 	/*
 	 * Order all writes to buffer before the commit count update that will
 	 * determine that the subbuffer is full.
 	 */
-	if (config->ipi == RING_BUFFER_IPI_BARRIER) {
-		/*
-		 * Must write slot data before incrementing commit count.  This
-		 * compiler barrier is upgraded into a smp_mb() by the IPI sent
-		 * by get_subbuf().
-		 */
-		barrier();
-	} else
-		smp_wmb();
+	cmm_smp_wmb();
 	v_add(config, config->cb.subbuffer_header_size(),
-	      &buf->commit_hot[oldidx].cc);
-	commit_count = v_read(config, &buf->commit_hot[oldidx].cc);
+	      &shmp_index(handle, buf->commit_hot, oldidx)->cc);
+	commit_count = v_read(config, &shmp_index(handle, buf->commit_hot, oldidx)->cc);
 	/* Check if the written buffer has to be delivered */
 	lib_ring_buffer_check_deliver(config, buf, chan, offsets->old,
-				      commit_count, oldidx);
+				      commit_count, oldidx, handle);
 	lib_ring_buffer_write_commit_counter(config, buf, chan, oldidx,
 					     offsets->old, commit_count,
-					     config->cb.subbuffer_header_size());
+					     config->cb.subbuffer_header_size(),
+					     handle);
 }
 
 /*
@@ -1247,39 +1066,33 @@ void lib_ring_buffer_switch_old_start(struct lib_ring_buffer *buf,
  * subbuffer.
  */
 static
-void lib_ring_buffer_switch_old_end(struct lib_ring_buffer *buf,
+void lib_ring_buffer_switch_old_end(struct lttng_ust_lib_ring_buffer *buf,
 				    struct channel *chan,
 				    struct switch_offsets *offsets,
-				    u64 tsc)
+				    uint64_t tsc,
+				    struct lttng_ust_shm_handle *handle)
 {
-	const struct lib_ring_buffer_config *config = chan->backend.config;
+	const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
 	unsigned long oldidx = subbuf_index(offsets->old - 1, chan);
 	unsigned long commit_count, padding_size, data_size;
 
 	data_size = subbuf_offset(offsets->old - 1, chan) + 1;
 	padding_size = chan->backend.subbuf_size - data_size;
-	subbuffer_set_data_size(config, &buf->backend, oldidx, data_size);
+	subbuffer_set_data_size(config, &buf->backend, oldidx, data_size,
+				handle);
 
 	/*
 	 * Order all writes to buffer before the commit count update that will
 	 * determine that the subbuffer is full.
 	 */
-	if (config->ipi == RING_BUFFER_IPI_BARRIER) {
-		/*
-		 * Must write slot data before incrementing commit count.  This
-		 * compiler barrier is upgraded into a smp_mb() by the IPI sent
-		 * by get_subbuf().
-		 */
-		barrier();
-	} else
-		smp_wmb();
-	v_add(config, padding_size, &buf->commit_hot[oldidx].cc);
-	commit_count = v_read(config, &buf->commit_hot[oldidx].cc);
+	cmm_smp_wmb();
+	v_add(config, padding_size, &shmp_index(handle, buf->commit_hot, oldidx)->cc);
+	commit_count = v_read(config, &shmp_index(handle, buf->commit_hot, oldidx)->cc);
 	lib_ring_buffer_check_deliver(config, buf, chan, offsets->old - 1,
-				      commit_count, oldidx);
+				      commit_count, oldidx, handle);
 	lib_ring_buffer_write_commit_counter(config, buf, chan, oldidx,
 					     offsets->old, commit_count,
-					     padding_size);
+					     padding_size, handle);
 }
 
 /*
@@ -1290,39 +1103,33 @@ void lib_ring_buffer_switch_old_end(struct lib_ring_buffer *buf,
  * that this code is executed before the deliver of this sub-buffer.
  */
 static
-void lib_ring_buffer_switch_new_start(struct lib_ring_buffer *buf,
+void lib_ring_buffer_switch_new_start(struct lttng_ust_lib_ring_buffer *buf,
 				      struct channel *chan,
 				      struct switch_offsets *offsets,
-				      u64 tsc)
+				      uint64_t tsc,
+				      struct lttng_ust_shm_handle *handle)
 {
-	const struct lib_ring_buffer_config *config = chan->backend.config;
+	const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
 	unsigned long beginidx = subbuf_index(offsets->begin, chan);
 	unsigned long commit_count;
 
-	config->cb.buffer_begin(buf, tsc, beginidx);
+	config->cb.buffer_begin(buf, tsc, beginidx, handle);
 
 	/*
 	 * Order all writes to buffer before the commit count update that will
 	 * determine that the subbuffer is full.
 	 */
-	if (config->ipi == RING_BUFFER_IPI_BARRIER) {
-		/*
-		 * Must write slot data before incrementing commit count.  This
-		 * compiler barrier is upgraded into a smp_mb() by the IPI sent
-		 * by get_subbuf().
-		 */
-		barrier();
-	} else
-		smp_wmb();
+	cmm_smp_wmb();
 	v_add(config, config->cb.subbuffer_header_size(),
-	      &buf->commit_hot[beginidx].cc);
-	commit_count = v_read(config, &buf->commit_hot[beginidx].cc);
+	      &shmp_index(handle, buf->commit_hot, beginidx)->cc);
+	commit_count = v_read(config, &shmp_index(handle, buf->commit_hot, beginidx)->cc);
 	/* Check if the written buffer has to be delivered */
 	lib_ring_buffer_check_deliver(config, buf, chan, offsets->begin,
-				      commit_count, beginidx);
+				      commit_count, beginidx, handle);
 	lib_ring_buffer_write_commit_counter(config, buf, chan, beginidx,
 					     offsets->begin, commit_count,
-					     config->cb.subbuffer_header_size());
+					     config->cb.subbuffer_header_size(),
+					     handle);
 }
 
 /*
@@ -1332,39 +1139,33 @@ void lib_ring_buffer_switch_new_start(struct lib_ring_buffer *buf,
  * have to do the deliver themselves.
  */
 static
-void lib_ring_buffer_switch_new_end(struct lib_ring_buffer *buf,
-					    struct channel *chan,
-					    struct switch_offsets *offsets,
-					    u64 tsc)
+void lib_ring_buffer_switch_new_end(struct lttng_ust_lib_ring_buffer *buf,
+				    struct channel *chan,
+				    struct switch_offsets *offsets,
+				    uint64_t tsc,
+				    struct lttng_ust_shm_handle *handle)
 {
-	const struct lib_ring_buffer_config *config = chan->backend.config;
+	const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
 	unsigned long endidx = subbuf_index(offsets->end - 1, chan);
 	unsigned long commit_count, padding_size, data_size;
 
 	data_size = subbuf_offset(offsets->end - 1, chan) + 1;
 	padding_size = chan->backend.subbuf_size - data_size;
-	subbuffer_set_data_size(config, &buf->backend, endidx, data_size);
+	subbuffer_set_data_size(config, &buf->backend, endidx, data_size,
+				handle);
 
 	/*
 	 * Order all writes to buffer before the commit count update that will
 	 * determine that the subbuffer is full.
 	 */
-	if (config->ipi == RING_BUFFER_IPI_BARRIER) {
-		/*
-		 * Must write slot data before incrementing commit count.  This
-		 * compiler barrier is upgraded into a smp_mb() by the IPI sent
-		 * by get_subbuf().
-		 */
-		barrier();
-	} else
-		smp_wmb();
-	v_add(config, padding_size, &buf->commit_hot[endidx].cc);
-	commit_count = v_read(config, &buf->commit_hot[endidx].cc);
+	cmm_smp_wmb();
+	v_add(config, padding_size, &shmp_index(handle, buf->commit_hot, endidx)->cc);
+	commit_count = v_read(config, &shmp_index(handle, buf->commit_hot, endidx)->cc);
 	lib_ring_buffer_check_deliver(config, buf, chan, offsets->end - 1,
-				  commit_count, endidx);
+				  commit_count, endidx, handle);
 	lib_ring_buffer_write_commit_counter(config, buf, chan, endidx,
 					     offsets->end, commit_count,
-					     padding_size);
+					     padding_size, handle);
 }
 
 /*
@@ -1374,12 +1175,12 @@ void lib_ring_buffer_switch_new_end(struct lib_ring_buffer *buf,
  */
 static
 int lib_ring_buffer_try_switch_slow(enum switch_mode mode,
-				    struct lib_ring_buffer *buf,
+				    struct lttng_ust_lib_ring_buffer *buf,
 				    struct channel *chan,
 				    struct switch_offsets *offsets,
-				    u64 *tsc)
+				    uint64_t *tsc)
 {
-	const struct lib_ring_buffer_config *config = chan->backend.config;
+	const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
 	unsigned long off;
 
 	offsets->begin = v_read(config, &buf->offset);
@@ -1400,13 +1201,13 @@ int lib_ring_buffer_try_switch_slow(enum switch_mode mode,
 	 * The next record that reserves space will be responsible for
 	 * populating the following subbuffer header. We choose not to populate
 	 * the next subbuffer header here because we want to be able to use
-	 * SWITCH_ACTIVE for periodical buffer flush and CPU tick_nohz stop
-	 * buffer flush, which must guarantee that all the buffer content
-	 * (records and header timestamps) are visible to the reader. This is
-	 * required for quiescence guarantees for the fusion merge.
+	 * SWITCH_ACTIVE for periodical buffer flush, which must
+	 * guarantee that all the buffer content (records and header
+	 * timestamps) are visible to the reader. This is required for
+	 * quiescence guarantees for the fusion merge.
 	 */
 	if (mode == SWITCH_FLUSH || off > 0) {
-		if (unlikely(off == 0)) {
+		if (caa_unlikely(off == 0)) {
 			/*
 			 * The client does not save any header information.
 			 * Don't switch empty subbuffer on finalize, because it
@@ -1435,13 +1236,14 @@ int lib_ring_buffer_try_switch_slow(enum switch_mode mode,
  * operations, this function must be called from the CPU which owns the buffer
  * for a ACTIVE flush.
  */
-void lib_ring_buffer_switch_slow(struct lib_ring_buffer *buf, enum switch_mode mode)
+void lib_ring_buffer_switch_slow(struct lttng_ust_lib_ring_buffer *buf, enum switch_mode mode,
+				 struct lttng_ust_shm_handle *handle)
 {
-	struct channel *chan = buf->backend.chan;
-	const struct lib_ring_buffer_config *config = chan->backend.config;
+	struct channel *chan = shmp(handle, buf->backend.chan);
+	const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
 	struct switch_offsets offsets;
 	unsigned long oldidx;
-	u64 tsc;
+	uint64_t tsc;
 
 	offsets.size = 0;
 
@@ -1469,22 +1271,21 @@ void lib_ring_buffer_switch_slow(struct lib_ring_buffer *buf, enum switch_mode m
 	lib_ring_buffer_reserve_push_reader(buf, chan, offsets.old);
 
 	oldidx = subbuf_index(offsets.old, chan);
-	lib_ring_buffer_clear_noref(config, &buf->backend, oldidx);
+	lib_ring_buffer_clear_noref(config, &buf->backend, oldidx, handle);
 
 	/*
 	 * May need to populate header start on SWITCH_FLUSH.
 	 */
 	if (offsets.switch_old_start) {
-		lib_ring_buffer_switch_old_start(buf, chan, &offsets, tsc);
+		lib_ring_buffer_switch_old_start(buf, chan, &offsets, tsc, handle);
 		offsets.old += config->cb.subbuffer_header_size();
 	}
 
 	/*
 	 * Switch old subbuffer.
 	 */
-	lib_ring_buffer_switch_old_end(buf, chan, &offsets, tsc);
+	lib_ring_buffer_switch_old_end(buf, chan, &offsets, tsc, handle);
 }
-EXPORT_SYMBOL_GPL(lib_ring_buffer_switch_slow);
 
 /*
  * Returns :
@@ -1494,12 +1295,13 @@ EXPORT_SYMBOL_GPL(lib_ring_buffer_switch_slow);
  * -EIO if data cannot be written into the buffer for any other reason.
  */
 static
-int lib_ring_buffer_try_reserve_slow(struct lib_ring_buffer *buf,
+int lib_ring_buffer_try_reserve_slow(struct lttng_ust_lib_ring_buffer *buf,
 				     struct channel *chan,
 				     struct switch_offsets *offsets,
-				     struct lib_ring_buffer_ctx *ctx)
+				     struct lttng_ust_lib_ring_buffer_ctx *ctx)
 {
-	const struct lib_ring_buffer_config *config = chan->backend.config;
+	const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
+	struct lttng_ust_shm_handle *handle = ctx->handle;
 	unsigned long reserve_commit_diff;
 
 	offsets->begin = v_read(config, &buf->offset);
@@ -1516,7 +1318,7 @@ int lib_ring_buffer_try_reserve_slow(struct lib_ring_buffer *buf,
 	if (last_tsc_overflow(config, buf, ctx->tsc))
 		ctx->rflags |= RING_BUFFER_RFLAG_FULL_TSC;
 
-	if (unlikely(subbuf_offset(offsets->begin, ctx->chan) == 0)) {
+	if (caa_unlikely(subbuf_offset(offsets->begin, ctx->chan) == 0)) {
 		offsets->switch_new_start = 1;		/* For offsets->begin */
 	} else {
 		offsets->size = config->cb.record_header_size(config, chan,
@@ -1527,19 +1329,19 @@ int lib_ring_buffer_try_reserve_slow(struct lib_ring_buffer *buf,
 			lib_ring_buffer_align(offsets->begin + offsets->size,
 					      ctx->largest_align)
 			+ ctx->data_size;
-		if (unlikely(subbuf_offset(offsets->begin, chan) +
+		if (caa_unlikely(subbuf_offset(offsets->begin, chan) +
 			     offsets->size > chan->backend.subbuf_size)) {
 			offsets->switch_old_end = 1;	/* For offsets->old */
 			offsets->switch_new_start = 1;	/* For offsets->begin */
 		}
 	}
-	if (unlikely(offsets->switch_new_start)) {
+	if (caa_unlikely(offsets->switch_new_start)) {
 		unsigned long sb_index;
 
 		/*
 		 * We are typically not filling the previous buffer completely.
 		 */
-		if (likely(offsets->switch_old_end))
+		if (caa_likely(offsets->switch_old_end))
 			offsets->begin = subbuf_align(offsets->begin, chan);
 		offsets->begin = offsets->begin
 				 + config->cb.subbuffer_header_size();
@@ -1549,20 +1351,28 @@ int lib_ring_buffer_try_reserve_slow(struct lib_ring_buffer *buf,
 		  (buf_trunc(offsets->begin, chan)
 		   >> chan->backend.num_subbuf_order)
 		  - ((unsigned long) v_read(config,
-					    &buf->commit_cold[sb_index].cc_sb)
+					    &shmp_index(handle, buf->commit_cold, sb_index)->cc_sb)
 		     & chan->commit_count_mask);
-		if (likely(reserve_commit_diff == 0)) {
+		if (caa_likely(reserve_commit_diff == 0)) {
 			/* Next subbuffer not being written to. */
-			if (unlikely(config->mode != RING_BUFFER_OVERWRITE &&
+			if (caa_unlikely(config->mode != RING_BUFFER_OVERWRITE &&
 				subbuf_trunc(offsets->begin, chan)
 				 - subbuf_trunc((unsigned long)
-				     atomic_long_read(&buf->consumed), chan)
+				     uatomic_read(&buf->consumed), chan)
 				>= chan->backend.buf_size)) {
+				unsigned long nr_lost;
+
 				/*
 				 * We do not overwrite non consumed buffers
 				 * and we are full : record is lost.
 				 */
+				nr_lost = v_read(config, &buf->records_lost_full);
 				v_inc(config, &buf->records_lost_full);
+				if ((nr_lost & (DBG_PRINT_NR_LOST - 1)) == 0) {
+					DBG("%lu or more records lost in (%s:%d) (buffer full)\n",
+						nr_lost + 1, chan->backend.name,
+						buf->backend.cpu);
+				}
 				return -ENOBUFS;
 			} else {
 				/*
@@ -1573,13 +1383,21 @@ int lib_ring_buffer_try_reserve_slow(struct lib_ring_buffer *buf,
 				 */
 			}
 		} else {
+			unsigned long nr_lost;
+
 			/*
 			 * Next subbuffer reserve offset does not match the
 			 * commit offset. Drop record in producer-consumer and
 			 * overwrite mode. Caused by either a writer OOPS or too
 			 * many nested writes over a reserve/commit pair.
 			 */
+			nr_lost = v_read(config, &buf->records_lost_wrap);
 			v_inc(config, &buf->records_lost_wrap);
+			if ((nr_lost & (DBG_PRINT_NR_LOST - 1)) == 0) {
+				DBG("%lu or more records lost in (%s:%d) (wrap-around)\n",
+					nr_lost + 1, chan->backend.name,
+					buf->backend.cpu);
+			}
 			return -EIO;
 		}
 		offsets->size =
@@ -1591,13 +1409,22 @@ int lib_ring_buffer_try_reserve_slow(struct lib_ring_buffer *buf,
 			lib_ring_buffer_align(offsets->begin + offsets->size,
 					      ctx->largest_align)
 			+ ctx->data_size;
-		if (unlikely(subbuf_offset(offsets->begin, chan)
+		if (caa_unlikely(subbuf_offset(offsets->begin, chan)
 			     + offsets->size > chan->backend.subbuf_size)) {
+			unsigned long nr_lost;
+
 			/*
 			 * Record too big for subbuffers, report error, don't
 			 * complete the sub-buffer switch.
 			 */
+			nr_lost = v_read(config, &buf->records_lost_big);
 			v_inc(config, &buf->records_lost_big);
+			if ((nr_lost & (DBG_PRINT_NR_LOST - 1)) == 0) {
+				DBG("%lu or more records lost in (%s:%d) record size "
+					" of %zu bytes is too large for buffer\n",
+					nr_lost + 1, chan->backend.name,
+					buf->backend.cpu, offsets->size);
+			}
 			return -ENOSPC;
 		} else {
 			/*
@@ -1613,7 +1440,7 @@ int lib_ring_buffer_try_reserve_slow(struct lib_ring_buffer *buf,
 	}
 	offsets->end = offsets->begin + offsets->size;
 
-	if (unlikely(subbuf_offset(offsets->end, chan) == 0)) {
+	if (caa_unlikely(subbuf_offset(offsets->end, chan) == 0)) {
 		/*
 		 * The offset_end will fall at the very beginning of the next
 		 * subbuffer.
@@ -1631,18 +1458,19 @@ int lib_ring_buffer_try_reserve_slow(struct lib_ring_buffer *buf,
  * -EIO for other errors, else returns 0.
  * It will take care of sub-buffer switching.
  */
-int lib_ring_buffer_reserve_slow(struct lib_ring_buffer_ctx *ctx)
+int lib_ring_buffer_reserve_slow(struct lttng_ust_lib_ring_buffer_ctx *ctx)
 {
 	struct channel *chan = ctx->chan;
-	const struct lib_ring_buffer_config *config = chan->backend.config;
-	struct lib_ring_buffer *buf;
+	struct lttng_ust_shm_handle *handle = ctx->handle;
+	const struct lttng_ust_lib_ring_buffer_config *config = &chan->backend.config;
+	struct lttng_ust_lib_ring_buffer *buf;
 	struct switch_offsets offsets;
 	int ret;
 
 	if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
-		buf = per_cpu_ptr(chan->backend.buf, ctx->cpu);
+		buf = shmp(handle, chan->backend.buf[ctx->cpu].shmp);
 	else
-		buf = chan->backend.buf;
+		buf = shmp(handle, chan->backend.buf[0].shmp);
 	ctx->buf = buf;
 
 	offsets.size = 0;
@@ -1650,9 +1478,9 @@ int lib_ring_buffer_reserve_slow(struct lib_ring_buffer_ctx *ctx)
 	do {
 		ret = lib_ring_buffer_try_reserve_slow(buf, chan, &offsets,
 						       ctx);
-		if (unlikely(ret))
+		if (caa_unlikely(ret))
 			return ret;
-	} while (unlikely(v_cmpxchg(config, &buf->offset, offsets.old,
+	} while (caa_unlikely(v_cmpxchg(config, &buf->offset, offsets.old,
 				    offsets.end)
 			  != offsets.old));
 
@@ -1673,29 +1501,38 @@ int lib_ring_buffer_reserve_slow(struct lib_ring_buffer_ctx *ctx)
 	 * Clear noref flag for this subbuffer.
 	 */
 	lib_ring_buffer_clear_noref(config, &buf->backend,
-				    subbuf_index(offsets.end - 1, chan));
+				    subbuf_index(offsets.end - 1, chan),
+				    handle);
 
 	/*
 	 * Switch old subbuffer if needed.
 	 */
-	if (unlikely(offsets.switch_old_end)) {
+	if (caa_unlikely(offsets.switch_old_end)) {
 		lib_ring_buffer_clear_noref(config, &buf->backend,
-					    subbuf_index(offsets.old - 1, chan));
-		lib_ring_buffer_switch_old_end(buf, chan, &offsets, ctx->tsc);
+					    subbuf_index(offsets.old - 1, chan),
+					    handle);
+		lib_ring_buffer_switch_old_end(buf, chan, &offsets, ctx->tsc, handle);
 	}
 
 	/*
 	 * Populate new subbuffer.
 	 */
-	if (unlikely(offsets.switch_new_start))
-		lib_ring_buffer_switch_new_start(buf, chan, &offsets, ctx->tsc);
+	if (caa_unlikely(offsets.switch_new_start))
+		lib_ring_buffer_switch_new_start(buf, chan, &offsets, ctx->tsc, handle);
 
-	if (unlikely(offsets.switch_new_end))
-		lib_ring_buffer_switch_new_end(buf, chan, &offsets, ctx->tsc);
+	if (caa_unlikely(offsets.switch_new_end))
+		lib_ring_buffer_switch_new_end(buf, chan, &offsets, ctx->tsc, handle);
 
 	ctx->slot_size = offsets.size;
 	ctx->pre_offset = offsets.begin;
 	ctx->buf_offset = offsets.begin + offsets.pre_header_padding;
 	return 0;
 }
-EXPORT_SYMBOL_GPL(lib_ring_buffer_reserve_slow);
+
+/*
+ * Force a read (imply TLS fixup for dlopen) of TLS variables.
+ */
+void lttng_fixup_ringbuffer_tls(void)
+{
+	asm volatile ("" : : "m" (lib_ring_buffer_nesting));
+}