1 files changed, 586 insertions, 188 deletions

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 2f76193c3489..7f69cfeaadf7 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -16,14 +16,100 @@
 #include <linux/list.h>
 #include <linux/fs.h>
 
+#include "trace.h"
+
+/*
+ * A fast way to enable or disable all ring buffers is to
+ * call tracing_on or tracing_off. Turning off the ring buffers
+ * prevents all ring buffers from being recorded to.
+ * Turning this switch on, makes it OK to write to the
+ * ring buffer, if the ring buffer is enabled itself.
+ *
+ * There's three layers that must be on in order to write
+ * to the ring buffer.
+ *
+ * 1) This global flag must be set.
+ * 2) The ring buffer must be enabled for recording.
+ * 3) The per cpu buffer must be enabled for recording.
+ *
+ * In case of an anomaly, this global flag has a bit set that
+ * will permantly disable all ring buffers.
+ */
+
+/*
+ * Global flag to disable all recording to ring buffers
+ *  This has two bits: ON, DISABLED
+ *
+ *  ON   DISABLED
+ * ---- ----------
+ *   0      0        : ring buffers are off
+ *   1      0        : ring buffers are on
+ *   X      1        : ring buffers are permanently disabled
+ */
+
+enum {
+        RB_BUFFERS_ON_BIT       = 0,
+        RB_BUFFERS_DISABLED_BIT = 1,
+};
+
+enum {
+        RB_BUFFERS_ON           = 1 << RB_BUFFERS_ON_BIT,
+        RB_BUFFERS_DISABLED     = 1 << RB_BUFFERS_DISABLED_BIT,
+};
+
+static long ring_buffer_flags __read_mostly = RB_BUFFERS_ON;
+
+/**
+ * tracing_on - enable all tracing buffers
+ *
+ * This function enables all tracing buffers that may have been
+ * disabled with tracing_off.
+ */
+void tracing_on(void)
+{
+        set_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags);
+}
+
+/**
+ * tracing_off - turn off all tracing buffers
+ *
+ * This function stops all tracing buffers from recording data.
+ * It does not disable any overhead the tracers themselves may
+ * be causing. This function simply causes all recording to
+ * the ring buffers to fail.
+ */
+void tracing_off(void)
+{
+        clear_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags);
+}
+
+/**
+ * tracing_off_permanent - permanently disable ring buffers
+ *
+ * This function, once called, will disable all ring buffers
+ * permanenty.
+ */
+void tracing_off_permanent(void)
+{
+        set_bit(RB_BUFFERS_DISABLED_BIT, &ring_buffer_flags);
+}
+
+#include "trace.h"
+
 /* Up this if you want to test the TIME_EXTENTS and normalization */
 #define DEBUG_SHIFT 0
 
 /* FIXME!!! */
 u64 ring_buffer_time_stamp(int cpu)
 {
+        u64 time;
+
+        preempt_disable_notrace();
         /* shift to debug/test normalization and TIME_EXTENTS */
-        return sched_clock() << DEBUG_SHIFT;
+        time = sched_clock() << DEBUG_SHIFT;
+        preempt_enable_notrace();
+
+        return time;
 }
 
 void ring_buffer_normalize_time_stamp(int cpu, u64 *ts)
@@ -109,20 +195,24 @@ void *ring_buffer_event_data(struct ring_buffer_event *event)
 #define TS_MASK         ((1ULL << TS_SHIFT) - 1)
 #define TS_DELTA_TEST   (~TS_MASK)
 
-/*
- * This hack stolen from mm/slob.c.
- * We can store per page timing information in the page frame of the page.
- * Thanks to Peter Zijlstra for suggesting this idea.
- */
-struct buffer_page {
+struct buffer_data_page {
         u64              time_stamp;    /* page time stamp */
-        local_t          write;         /* index for next write */
         local_t          commit;        /* write commited index */
+        unsigned char    data[];        /* data of buffer page */
+};
+
+struct buffer_page {
+        local_t          write;         /* index for next write */
         unsigned         read;          /* index for next read */
         struct list_head list;          /* list of free pages */
-        void *page;                     /* Actual data page */
+        struct buffer_data_page *page;  /* Actual data page */
 };
 
+static void rb_init_page(struct buffer_data_page *bpage)
+{
+        local_set(&bpage->commit, 0);
+}
+
 /*
  * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
  * this issue out.
@@ -144,7 +234,7 @@ static inline int test_time_stamp(u64 delta)
         return 0;
 }
 
-#define BUF_PAGE_SIZE PAGE_SIZE
+#define BUF_PAGE_SIZE (PAGE_SIZE - sizeof(struct buffer_data_page))
 
 /*
  * head_page == tail_page && head == tail then buffer is empty.
@@ -152,7 +242,8 @@ static inline int test_time_stamp(u64 delta)
 struct ring_buffer_per_cpu {
         int                             cpu;
         struct ring_buffer              *buffer;
-        spinlock_t                      lock;
+        spinlock_t                      reader_lock; /* serialize readers */
+        raw_spinlock_t                  lock;
         struct lock_class_key           lock_key;
         struct list_head                pages;
         struct buffer_page              *head_page;     /* read from head */
@@ -186,32 +277,16 @@ struct ring_buffer_iter {
         u64                             read_stamp;
 };
 
+/* buffer may be either ring_buffer or ring_buffer_per_cpu */
 #define RB_WARN_ON(buffer, cond)                                \
-        do {                                                    \
-                if (unlikely(cond)) {                           \
-                        atomic_inc(&buffer->record_disabled);   \
-                        WARN_ON(1);                             \
-                }                                               \
-        } while (0)
-
-#define RB_WARN_ON_RET(buffer, cond)                            \
-        do {                                                    \
-                if (unlikely(cond)) {                           \
-                        atomic_inc(&buffer->record_disabled);   \
-                        WARN_ON(1);                             \
-                        return -1;                              \
-                }                                               \
-        } while (0)
-
-#define RB_WARN_ON_ONCE(buffer, cond)                           \
-        do {                                                    \
-                static int once;                                \
-                if (unlikely(cond) && !once) {                  \
-                        once++;                                 \
+        ({                                                      \
+                int _____ret = unlikely(cond);                  \
+                if (_____ret) {                                 \
                         atomic_inc(&buffer->record_disabled);   \
                         WARN_ON(1);                             \
                 }                                               \
-        } while (0)
+                _____ret;                                       \
+        })
 
 /**
  * check_pages - integrity check of buffer pages
@@ -223,16 +298,20 @@ struct ring_buffer_iter {
 static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
 {
         struct list_head *head = &cpu_buffer->pages;
-        struct buffer_page *page, *tmp;
+        struct buffer_page *bpage, *tmp;
 
-        RB_WARN_ON_RET(cpu_buffer, head->next->prev != head);
-        RB_WARN_ON_RET(cpu_buffer, head->prev->next != head);
+        if (RB_WARN_ON(cpu_buffer, head->next->prev != head))
+                return -1;
+        if (RB_WARN_ON(cpu_buffer, head->prev->next != head))
+                return -1;
 
-        list_for_each_entry_safe(page, tmp, head, list) {
-                RB_WARN_ON_RET(cpu_buffer,
-                               page->list.next->prev != &page->list);
-                RB_WARN_ON_RET(cpu_buffer,
-                               page->list.prev->next != &page->list);
+        list_for_each_entry_safe(bpage, tmp, head, list) {
+                if (RB_WARN_ON(cpu_buffer,
+                               bpage->list.next->prev != &bpage->list))
+                        return -1;
+                if (RB_WARN_ON(cpu_buffer,
+                               bpage->list.prev->next != &bpage->list))
+                        return -1;
         }
 
         return 0;
@@ -242,22 +321,23 @@ static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
                              unsigned nr_pages)
 {
         struct list_head *head = &cpu_buffer->pages;
-        struct buffer_page *page, *tmp;
+        struct buffer_page *bpage, *tmp;
         unsigned long addr;
         LIST_HEAD(pages);
         unsigned i;
 
         for (i = 0; i < nr_pages; i++) {
-                page = kzalloc_node(ALIGN(sizeof(*page), cache_line_size()),
+                bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
                                     GFP_KERNEL, cpu_to_node(cpu_buffer->cpu));
-                if (!page)
+                if (!bpage)
                         goto free_pages;
-                list_add(&page->list, &pages);
+                list_add(&bpage->list, &pages);
 
                 addr = __get_free_page(GFP_KERNEL);
                 if (!addr)
                         goto free_pages;
-                page->page = (void *)addr;
+                bpage->page = (void *)addr;
+                rb_init_page(bpage->page);
         }
 
         list_splice(&pages, head);
@@ -267,9 +347,9 @@ static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
         return 0;
 
  free_pages:
-        list_for_each_entry_safe(page, tmp, &pages, list) {
-                list_del_init(&page->list);
-                free_buffer_page(page);
+        list_for_each_entry_safe(bpage, tmp, &pages, list) {
+                list_del_init(&bpage->list);
+                free_buffer_page(bpage);
         }
         return -ENOMEM;
 }
@@ -278,7 +358,7 @@ static struct ring_buffer_per_cpu *
 rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu)
 {
         struct ring_buffer_per_cpu *cpu_buffer;
-        struct buffer_page *page;
+        struct buffer_page *bpage;
         unsigned long addr;
         int ret;
 
@@ -289,19 +369,21 @@ rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu)
 
         cpu_buffer->cpu = cpu;
         cpu_buffer->buffer = buffer;
-        spin_lock_init(&cpu_buffer->lock);
+        spin_lock_init(&cpu_buffer->reader_lock);
+        cpu_buffer->lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
         INIT_LIST_HEAD(&cpu_buffer->pages);
 
-        page = kzalloc_node(ALIGN(sizeof(*page), cache_line_size()),
+        bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
                             GFP_KERNEL, cpu_to_node(cpu));
-        if (!page)
+        if (!bpage)
                 goto fail_free_buffer;
 
-        cpu_buffer->reader_page = page;
+        cpu_buffer->reader_page = bpage;
         addr = __get_free_page(GFP_KERNEL);
         if (!addr)
                 goto fail_free_reader;
-        page->page = (void *)addr;
+        bpage->page = (void *)addr;
+        rb_init_page(bpage->page);
 
         INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
 
@@ -326,14 +408,14 @@ rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu)
 static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
 {
         struct list_head *head = &cpu_buffer->pages;
-        struct buffer_page *page, *tmp;
+        struct buffer_page *bpage, *tmp;
 
         list_del_init(&cpu_buffer->reader_page->list);
         free_buffer_page(cpu_buffer->reader_page);
 
-        list_for_each_entry_safe(page, tmp, head, list) {
-                list_del_init(&page->list);
-                free_buffer_page(page);
+        list_for_each_entry_safe(bpage, tmp, head, list) {
+                list_del_init(&bpage->list);
+                free_buffer_page(bpage);
         }
         kfree(cpu_buffer);
 }
@@ -430,7 +512,7 @@ static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
 static void
 rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages)
 {
-        struct buffer_page *page;
+        struct buffer_page *bpage;
         struct list_head *p;
         unsigned i;
 
@@ -438,13 +520,15 @@ rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages)
         synchronize_sched();
 
         for (i = 0; i < nr_pages; i++) {
-                BUG_ON(list_empty(&cpu_buffer->pages));
+                if (RB_WARN_ON(cpu_buffer, list_empty(&cpu_buffer->pages)))
+                        return;
                 p = cpu_buffer->pages.next;
-                page = list_entry(p, struct buffer_page, list);
-                list_del_init(&page->list);
-                free_buffer_page(page);
+                bpage = list_entry(p, struct buffer_page, list);
+                list_del_init(&bpage->list);
+                free_buffer_page(bpage);
         }
-        BUG_ON(list_empty(&cpu_buffer->pages));
+        if (RB_WARN_ON(cpu_buffer, list_empty(&cpu_buffer->pages)))
+                return;
 
         rb_reset_cpu(cpu_buffer);
 
@@ -458,7 +542,7 @@ static void
 rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer,
                 struct list_head *pages, unsigned nr_pages)
 {
-        struct buffer_page *page;
+        struct buffer_page *bpage;
         struct list_head *p;
         unsigned i;
 
@@ -466,11 +550,12 @@ rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer,
         synchronize_sched();
 
         for (i = 0; i < nr_pages; i++) {
-                BUG_ON(list_empty(pages));
+                if (RB_WARN_ON(cpu_buffer, list_empty(pages)))
+                        return;
                 p = pages->next;
-                page = list_entry(p, struct buffer_page, list);
-                list_del_init(&page->list);
-                list_add_tail(&page->list, &cpu_buffer->pages);
+                bpage = list_entry(p, struct buffer_page, list);
+                list_del_init(&bpage->list);
+                list_add_tail(&bpage->list, &cpu_buffer->pages);
         }
         rb_reset_cpu(cpu_buffer);
 
@@ -497,12 +582,18 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
 {
         struct ring_buffer_per_cpu *cpu_buffer;
         unsigned nr_pages, rm_pages, new_pages;
-        struct buffer_page *page, *tmp;
+        struct buffer_page *bpage, *tmp;
         unsigned long buffer_size;
         unsigned long addr;
         LIST_HEAD(pages);
         int i, cpu;
 
+        /*
+         * Always succeed at resizing a non-existent buffer:
+         */
+        if (!buffer)
+                return size;
+
         size = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
         size *= BUF_PAGE_SIZE;
         buffer_size = buffer->pages * BUF_PAGE_SIZE;
@@ -521,7 +612,10 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
         if (size < buffer_size) {
 
                 /* easy case, just free pages */
-                BUG_ON(nr_pages >= buffer->pages);
+                if (RB_WARN_ON(buffer, nr_pages >= buffer->pages)) {
+                        mutex_unlock(&buffer->mutex);
+                        return -1;
+                }
 
                 rm_pages = buffer->pages - nr_pages;
 
@@ -540,21 +634,26 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
          * add these pages to the cpu_buffers. Otherwise we just free
          * them all and return -ENOMEM;
          */
-        BUG_ON(nr_pages <= buffer->pages);
+        if (RB_WARN_ON(buffer, nr_pages <= buffer->pages)) {
+                mutex_unlock(&buffer->mutex);
+                return -1;
+        }
+
         new_pages = nr_pages - buffer->pages;
 
         for_each_buffer_cpu(buffer, cpu) {
                 for (i = 0; i < new_pages; i++) {
-                        page = kzalloc_node(ALIGN(sizeof(*page),
+                        bpage = kzalloc_node(ALIGN(sizeof(*bpage),
                                                   cache_line_size()),
                                             GFP_KERNEL, cpu_to_node(cpu));
-                        if (!page)
+                        if (!bpage)
                                 goto free_pages;
-                        list_add(&page->list, &pages);
+                        list_add(&bpage->list, &pages);
                         addr = __get_free_page(GFP_KERNEL);
                         if (!addr)
                                 goto free_pages;
-                        page->page = (void *)addr;
+                        bpage->page = (void *)addr;
+                        rb_init_page(bpage->page);
                 }
         }
 
@@ -563,7 +662,10 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
                 rb_insert_pages(cpu_buffer, &pages, new_pages);
         }
 
-        BUG_ON(!list_empty(&pages));
+        if (RB_WARN_ON(buffer, !list_empty(&pages))) {
+                mutex_unlock(&buffer->mutex);
+                return -1;
+        }
 
  out:
         buffer->pages = nr_pages;
@@ -572,10 +674,11 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
         return size;
 
  free_pages:
-        list_for_each_entry_safe(page, tmp, &pages, list) {
-                list_del_init(&page->list);
-                free_buffer_page(page);
+        list_for_each_entry_safe(bpage, tmp, &pages, list) {
+                list_del_init(&bpage->list);
+                free_buffer_page(bpage);
         }
+        mutex_unlock(&buffer->mutex);
         return -ENOMEM;
 }
 
@@ -584,9 +687,15 @@ static inline int rb_null_event(struct ring_buffer_event *event)
         return event->type == RINGBUF_TYPE_PADDING;
 }
 
-static inline void *__rb_page_index(struct buffer_page *page, unsigned index)
+static inline void *
+__rb_data_page_index(struct buffer_data_page *bpage, unsigned index)
 {
-        return page->page + index;
+        return bpage->data + index;
+}
+
+static inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
+{
+        return bpage->page->data + index;
 }
 
 static inline struct ring_buffer_event *
@@ -616,7 +725,7 @@ static inline unsigned rb_page_write(struct buffer_page *bpage)
 
 static inline unsigned rb_page_commit(struct buffer_page *bpage)
 {
-        return local_read(&bpage->commit);
+        return local_read(&bpage->page->commit);
 }
 
 /* Size is determined by what has been commited */
@@ -651,7 +760,8 @@ static void rb_update_overflow(struct ring_buffer_per_cpu *cpu_buffer)
              head += rb_event_length(event)) {
 
                 event = __rb_page_index(cpu_buffer->head_page, head);
-                BUG_ON(rb_null_event(event));
+                if (RB_WARN_ON(cpu_buffer, rb_null_event(event)))
+                        return;
                 /* Only count data entries */
                 if (event->type != RINGBUF_TYPE_DATA)
                         continue;
@@ -661,14 +771,14 @@ static void rb_update_overflow(struct ring_buffer_per_cpu *cpu_buffer)
 }
 
 static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
-                               struct buffer_page **page)
+                               struct buffer_page **bpage)
 {
-        struct list_head *p = (*page)->list.next;
+        struct list_head *p = (*bpage)->list.next;
 
         if (p == &cpu_buffer->pages)
                 p = p->next;
 
-        *page = list_entry(p, struct buffer_page, list);
+        *bpage = list_entry(p, struct buffer_page, list);
 }
 
 static inline unsigned
@@ -704,16 +814,18 @@ rb_set_commit_event(struct ring_buffer_per_cpu *cpu_buffer,
         addr &= PAGE_MASK;
 
         while (cpu_buffer->commit_page->page != (void *)addr) {
-                RB_WARN_ON(cpu_buffer,
-                           cpu_buffer->commit_page == cpu_buffer->tail_page);
-                cpu_buffer->commit_page->commit =
+                if (RB_WARN_ON(cpu_buffer,
+                          cpu_buffer->commit_page == cpu_buffer->tail_page))
+                        return;
+                cpu_buffer->commit_page->page->commit =
                         cpu_buffer->commit_page->write;
                 rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
-                cpu_buffer->write_stamp = cpu_buffer->commit_page->time_stamp;
+                cpu_buffer->write_stamp =
+                        cpu_buffer->commit_page->page->time_stamp;
         }
 
         /* Now set the commit to the event's index */
-        local_set(&cpu_buffer->commit_page->commit, index);
+        local_set(&cpu_buffer->commit_page->page->commit, index);
 }
 
 static inline void
@@ -728,16 +840,17 @@ rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
          * assign the commit to the tail.
          */
         while (cpu_buffer->commit_page != cpu_buffer->tail_page) {
-                cpu_buffer->commit_page->commit =
+                cpu_buffer->commit_page->page->commit =
                         cpu_buffer->commit_page->write;
                 rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
-                cpu_buffer->write_stamp = cpu_buffer->commit_page->time_stamp;
+                cpu_buffer->write_stamp =
+                        cpu_buffer->commit_page->page->time_stamp;
                 /* add barrier to keep gcc from optimizing too much */
                 barrier();
         }
         while (rb_commit_index(cpu_buffer) !=
                rb_page_write(cpu_buffer->commit_page)) {
-                cpu_buffer->commit_page->commit =
+                cpu_buffer->commit_page->page->commit =
                         cpu_buffer->commit_page->write;
                 barrier();
         }
@@ -745,7 +858,7 @@ rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
 
 static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
 {
-        cpu_buffer->read_stamp = cpu_buffer->reader_page->time_stamp;
+        cpu_buffer->read_stamp = cpu_buffer->reader_page->page->time_stamp;
         cpu_buffer->reader_page->read = 0;
 }
 
@@ -764,7 +877,7 @@ static inline void rb_inc_iter(struct ring_buffer_iter *iter)
         else
                 rb_inc_page(cpu_buffer, &iter->head_page);
 
-        iter->read_stamp = iter->head_page->time_stamp;
+        iter->read_stamp = iter->head_page->page->time_stamp;
         iter->head = 0;
 }
 
@@ -852,7 +965,8 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
         if (write > BUF_PAGE_SIZE) {
                 struct buffer_page *next_page = tail_page;
 
-                spin_lock_irqsave(&cpu_buffer->lock, flags);
+                local_irq_save(flags);
+                __raw_spin_lock(&cpu_buffer->lock);
 
                 rb_inc_page(cpu_buffer, &next_page);
 
@@ -860,7 +974,8 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
                 reader_page = cpu_buffer->reader_page;
 
                 /* we grabbed the lock before incrementing */
-                RB_WARN_ON(cpu_buffer, next_page == reader_page);
+                if (RB_WARN_ON(cpu_buffer, next_page == reader_page))
+                        goto out_unlock;
 
                 /*
                  * If for some reason, we had an interrupt storm that made
@@ -898,12 +1013,12 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
                  */
                 if (tail_page == cpu_buffer->tail_page) {
                         local_set(&next_page->write, 0);
-                        local_set(&next_page->commit, 0);
+                        local_set(&next_page->page->commit, 0);
                         cpu_buffer->tail_page = next_page;
 
                         /* reread the time stamp */
                         *ts = ring_buffer_time_stamp(cpu_buffer->cpu);
-                        cpu_buffer->tail_page->time_stamp = *ts;
+                        cpu_buffer->tail_page->page->time_stamp = *ts;
                 }
 
                 /*
@@ -928,7 +1043,8 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
                         rb_set_commit_to_write(cpu_buffer);
                 }
 
-                spin_unlock_irqrestore(&cpu_buffer->lock, flags);
+                __raw_spin_unlock(&cpu_buffer->lock);
+                local_irq_restore(flags);
 
                 /* fail and let the caller try again */
                 return ERR_PTR(-EAGAIN);
@@ -936,7 +1052,8 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
 
         /* We reserved something on the buffer */
 
-        BUG_ON(write > BUF_PAGE_SIZE);
+        if (RB_WARN_ON(cpu_buffer, write > BUF_PAGE_SIZE))
+                return NULL;
 
         event = __rb_page_index(tail_page, tail);
         rb_update_event(event, type, length);
@@ -946,12 +1063,13 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
          * this page's time stamp.
          */
         if (!tail && rb_is_commit(cpu_buffer, event))
-                cpu_buffer->commit_page->time_stamp = *ts;
+                cpu_buffer->commit_page->page->time_stamp = *ts;
 
         return event;
 
  out_unlock:
-        spin_unlock_irqrestore(&cpu_buffer->lock, flags);
+        __raw_spin_unlock(&cpu_buffer->lock);
+        local_irq_restore(flags);
         return NULL;
 }
 
@@ -996,7 +1114,7 @@ rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
                         event->time_delta = *delta & TS_MASK;
                         event->array[0] = *delta >> TS_SHIFT;
                 } else {
-                        cpu_buffer->commit_page->time_stamp = *ts;
+                        cpu_buffer->commit_page->page->time_stamp = *ts;
                         event->time_delta = 0;
                         event->array[0] = 0;
                 }
@@ -1034,10 +1152,8 @@ rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer,
          * storm or we have something buggy.
          * Bail!
          */
-        if (unlikely(++nr_loops > 1000)) {
-                RB_WARN_ON(cpu_buffer, 1);
+        if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
                 return NULL;
-        }
 
         ts = ring_buffer_time_stamp(cpu_buffer->cpu);
 
@@ -1133,12 +1249,14 @@ ring_buffer_lock_reserve(struct ring_buffer *buffer,
         struct ring_buffer_event *event;
         int cpu, resched;
 
+        if (ring_buffer_flags != RB_BUFFERS_ON)
+                return NULL;
+
         if (atomic_read(&buffer->record_disabled))
                 return NULL;
 
         /* If we are tracing schedule, we don't want to recurse */
-        resched = need_resched();
-        preempt_disable_notrace();
+        resched = ftrace_preempt_disable();
 
         cpu = raw_smp_processor_id();
 
@@ -1169,10 +1287,7 @@ ring_buffer_lock_reserve(struct ring_buffer *buffer,
         return event;
 
  out:
-        if (resched)
-                preempt_enable_notrace();
-        else
-                preempt_enable_notrace();
+        ftrace_preempt_enable(resched);
         return NULL;
 }
 
@@ -1214,12 +1329,9 @@ int ring_buffer_unlock_commit(struct ring_buffer *buffer,
         /*
          * Only the last preempt count needs to restore preemption.
          */
-        if (preempt_count() == 1) {
-                if (per_cpu(rb_need_resched, cpu))
-                        preempt_enable_no_resched_notrace();
-                else
-                        preempt_enable_notrace();
-        } else
+        if (preempt_count() == 1)
+                ftrace_preempt_enable(per_cpu(rb_need_resched, cpu));
+        else
                 preempt_enable_no_resched_notrace();
 
         return 0;
@@ -1249,11 +1361,13 @@ int ring_buffer_write(struct ring_buffer *buffer,
         int ret = -EBUSY;
         int cpu, resched;
 
+        if (ring_buffer_flags != RB_BUFFERS_ON)
+                return -EBUSY;
+
         if (atomic_read(&buffer->record_disabled))
                 return -EBUSY;
 
-        resched = need_resched();
-        preempt_disable_notrace();
+        resched = ftrace_preempt_disable();
 
         cpu = raw_smp_processor_id();
 
@@ -1279,10 +1393,7 @@ int ring_buffer_write(struct ring_buffer *buffer,
 
         ret = 0;
  out:
-        if (resched)
-                preempt_enable_no_resched_notrace();
-        else
-                preempt_enable_notrace();
+        ftrace_preempt_enable(resched);
 
         return ret;
 }
@@ -1441,14 +1552,7 @@ unsigned long ring_buffer_overruns(struct ring_buffer *buffer)
         return overruns;
 }
 
-/**
- * ring_buffer_iter_reset - reset an iterator
- * @iter: The iterator to reset
- *
- * Resets the iterator, so that it will start from the beginning
- * again.
- */
-void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
+static void rb_iter_reset(struct ring_buffer_iter *iter)
 {
         struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
 
@@ -1463,7 +1567,24 @@ void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
         if (iter->head)
                 iter->read_stamp = cpu_buffer->read_stamp;
         else
-                iter->read_stamp = iter->head_page->time_stamp;
+                iter->read_stamp = iter->head_page->page->time_stamp;
+}
+
+/**
+ * ring_buffer_iter_reset - reset an iterator
+ * @iter: The iterator to reset
+ *
+ * Resets the iterator, so that it will start from the beginning
+ * again.
+ */
+void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
+{
+        struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
+        unsigned long flags;
+
+        spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+        rb_iter_reset(iter);
+        spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
 }
 
 /**
@@ -1549,7 +1670,8 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
         unsigned long flags;
         int nr_loops = 0;
 
-        spin_lock_irqsave(&cpu_buffer->lock, flags);
+        local_irq_save(flags);
+        __raw_spin_lock(&cpu_buffer->lock);
 
  again:
         /*
@@ -1558,8 +1680,7 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
          * a case where we will loop three times. There should be no
          * reason to loop four times (that I know of).
          */
-        if (unlikely(++nr_loops > 3)) {
-                RB_WARN_ON(cpu_buffer, 1);
+        if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
                 reader = NULL;
                 goto out;
         }
@@ -1571,8 +1692,9 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
                 goto out;
 
         /* Never should we have an index greater than the size */
-        RB_WARN_ON(cpu_buffer,
-                   cpu_buffer->reader_page->read > rb_page_size(reader));
+        if (RB_WARN_ON(cpu_buffer,
+                       cpu_buffer->reader_page->read > rb_page_size(reader)))
+                goto out;
 
         /* check if we caught up to the tail */
         reader = NULL;
@@ -1589,7 +1711,7 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
         cpu_buffer->reader_page->list.prev = reader->list.prev;
 
         local_set(&cpu_buffer->reader_page->write, 0);
-        local_set(&cpu_buffer->reader_page->commit, 0);
+        local_set(&cpu_buffer->reader_page->page->commit, 0);
 
         /* Make the reader page now replace the head */
         reader->list.prev->next = &cpu_buffer->reader_page->list;
@@ -1611,7 +1733,8 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
         goto again;
 
  out:
-        spin_unlock_irqrestore(&cpu_buffer->lock, flags);
+        __raw_spin_unlock(&cpu_buffer->lock);
+        local_irq_restore(flags);
 
         return reader;
 }
@@ -1625,7 +1748,8 @@ static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
         reader = rb_get_reader_page(cpu_buffer);
 
         /* This function should not be called when buffer is empty */
-        BUG_ON(!reader);
+        if (RB_WARN_ON(cpu_buffer, !reader))
+                return;
 
         event = rb_reader_event(cpu_buffer);
 
@@ -1652,7 +1776,9 @@ static void rb_advance_iter(struct ring_buffer_iter *iter)
          * Check if we are at the end of the buffer.
          */
         if (iter->head >= rb_page_size(iter->head_page)) {
-                BUG_ON(iter->head_page == cpu_buffer->commit_page);
+                if (RB_WARN_ON(buffer,
+                               iter->head_page == cpu_buffer->commit_page))
+                        return;
                 rb_inc_iter(iter);
                 return;
         }
@@ -1665,8 +1791,10 @@ static void rb_advance_iter(struct ring_buffer_iter *iter)
          * This should not be called to advance the header if we are
          * at the tail of the buffer.
          */
-        BUG_ON((iter->head_page == cpu_buffer->commit_page) &&
-               (iter->head + length > rb_commit_index(cpu_buffer)));
+        if (RB_WARN_ON(cpu_buffer,
+                       (iter->head_page == cpu_buffer->commit_page) &&
+                       (iter->head + length > rb_commit_index(cpu_buffer))))
+                return;
 
         rb_update_iter_read_stamp(iter, event);
 
@@ -1678,17 +1806,8 @@ static void rb_advance_iter(struct ring_buffer_iter *iter)
                 rb_advance_iter(iter);
 }
 
-/**
- * ring_buffer_peek - peek at the next event to be read
- * @buffer: The ring buffer to read
- * @cpu: The cpu to peak at
- * @ts: The timestamp counter of this event.
- *
- * This will return the event that will be read next, but does
- * not consume the data.
- */
-struct ring_buffer_event *
-ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)
+static struct ring_buffer_event *
+rb_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)
 {
         struct ring_buffer_per_cpu *cpu_buffer;
         struct ring_buffer_event *event;
@@ -1709,10 +1828,8 @@ ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)
          * can have.  Nesting 10 deep of interrupts is clearly
          * an anomaly.
          */
-        if (unlikely(++nr_loops > 10)) {
-                RB_WARN_ON(cpu_buffer, 1);
+        if (RB_WARN_ON(cpu_buffer, ++nr_loops > 10))
                 return NULL;
-        }
 
         reader = rb_get_reader_page(cpu_buffer);
         if (!reader)
@@ -1750,16 +1867,8 @@ ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)
         return NULL;
 }
 
-/**
- * ring_buffer_iter_peek - peek at the next event to be read
- * @iter: The ring buffer iterator
- * @ts: The timestamp counter of this event.
- *
- * This will return the event that will be read next, but does
- * not increment the iterator.
- */
-struct ring_buffer_event *
-ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
+static struct ring_buffer_event *
+rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
 {
         struct ring_buffer *buffer;
         struct ring_buffer_per_cpu *cpu_buffer;
@@ -1781,10 +1890,8 @@ ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
          * can have. Nesting 10 deep of interrupts is clearly
          * an anomaly.
          */
-        if (unlikely(++nr_loops > 10)) {
-                RB_WARN_ON(cpu_buffer, 1);
+        if (RB_WARN_ON(cpu_buffer, ++nr_loops > 10))
                 return NULL;
-        }
 
         if (rb_per_cpu_empty(cpu_buffer))
                 return NULL;
@@ -1821,6 +1928,51 @@ ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
 }
 
 /**
+ * ring_buffer_peek - peek at the next event to be read
+ * @buffer: The ring buffer to read
+ * @cpu: The cpu to peak at
+ * @ts: The timestamp counter of this event.
+ *
+ * This will return the event that will be read next, but does
+ * not consume the data.
+ */
+struct ring_buffer_event *
+ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)
+{
+        struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
+        struct ring_buffer_event *event;
+        unsigned long flags;
+
+        spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+        event = rb_buffer_peek(buffer, cpu, ts);
+        spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+
+        return event;
+}
+
+/**
+ * ring_buffer_iter_peek - peek at the next event to be read
+ * @iter: The ring buffer iterator
+ * @ts: The timestamp counter of this event.
+ *
+ * This will return the event that will be read next, but does
+ * not increment the iterator.
+ */
+struct ring_buffer_event *
+ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
+{
+        struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
+        struct ring_buffer_event *event;
+        unsigned long flags;
+
+        spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+        event = rb_iter_peek(iter, ts);
+        spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+
+        return event;
+}
+
+/**
  * ring_buffer_consume - return an event and consume it
  * @buffer: The ring buffer to get the next event from
  *
@@ -1831,19 +1983,24 @@ ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
 struct ring_buffer_event *
 ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts)
 {
-        struct ring_buffer_per_cpu *cpu_buffer;
+        struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
         struct ring_buffer_event *event;
+        unsigned long flags;
 
         if (!cpu_isset(cpu, buffer->cpumask))
                 return NULL;
 
-        event = ring_buffer_peek(buffer, cpu, ts);
+        spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+
+        event = rb_buffer_peek(buffer, cpu, ts);
         if (!event)
-                return NULL;
+                goto out;
 
-        cpu_buffer = buffer->buffers[cpu];
         rb_advance_reader(cpu_buffer);
 
+ out:
+        spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+
         return event;
 }
 
@@ -1880,9 +2037,11 @@ ring_buffer_read_start(struct ring_buffer *buffer, int cpu)
         atomic_inc(&cpu_buffer->record_disabled);
         synchronize_sched();
 
-        spin_lock_irqsave(&cpu_buffer->lock, flags);
-        ring_buffer_iter_reset(iter);
-        spin_unlock_irqrestore(&cpu_buffer->lock, flags);
+        spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+        __raw_spin_lock(&cpu_buffer->lock);
+        rb_iter_reset(iter);
+        __raw_spin_unlock(&cpu_buffer->lock);
+        spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
 
         return iter;
 }
@@ -1914,12 +2073,17 @@ struct ring_buffer_event *
 ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts)
 {
         struct ring_buffer_event *event;
+        struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
+        unsigned long flags;
 
-        event = ring_buffer_iter_peek(iter, ts);
+        spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+        event = rb_iter_peek(iter, ts);
         if (!event)
-                return NULL;
+                goto out;
 
         rb_advance_iter(iter);
+ out:
+        spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
 
         return event;
 }
@@ -1939,7 +2103,7 @@ rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
         cpu_buffer->head_page
                 = list_entry(cpu_buffer->pages.next, struct buffer_page, list);
         local_set(&cpu_buffer->head_page->write, 0);
-        local_set(&cpu_buffer->head_page->commit, 0);
+        local_set(&cpu_buffer->head_page->page->commit, 0);
 
         cpu_buffer->head_page->read = 0;
 
@@ -1948,7 +2112,7 @@ rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
 
         INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
         local_set(&cpu_buffer->reader_page->write, 0);
-        local_set(&cpu_buffer->reader_page->commit, 0);
+        local_set(&cpu_buffer->reader_page->page->commit, 0);
         cpu_buffer->reader_page->read = 0;
 
         cpu_buffer->overrun = 0;
@@ -1968,11 +2132,15 @@ void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu)
         if (!cpu_isset(cpu, buffer->cpumask))
                 return;
 
-        spin_lock_irqsave(&cpu_buffer->lock, flags);
+        spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+
+        __raw_spin_lock(&cpu_buffer->lock);
 
         rb_reset_cpu(cpu_buffer);
 
-        spin_unlock_irqrestore(&cpu_buffer->lock, flags);
+        __raw_spin_unlock(&cpu_buffer->lock);
+
+        spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
 }
 
 /**
@@ -2070,3 +2238,233 @@ int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
         return 0;
 }
 
+static void rb_remove_entries(struct ring_buffer_per_cpu *cpu_buffer,
+                              struct buffer_data_page *bpage)
+{
+        struct ring_buffer_event *event;
+        unsigned long head;
+
+        __raw_spin_lock(&cpu_buffer->lock);
+        for (head = 0; head < local_read(&bpage->commit);
+             head += rb_event_length(event)) {
+
+                event = __rb_data_page_index(bpage, head);
+                if (RB_WARN_ON(cpu_buffer, rb_null_event(event)))
+                        return;
+                /* Only count data entries */
+                if (event->type != RINGBUF_TYPE_DATA)
+                        continue;
+                cpu_buffer->entries--;
+        }
+        __raw_spin_unlock(&cpu_buffer->lock);
+}
+
+/**
+ * ring_buffer_alloc_read_page - allocate a page to read from buffer
+ * @buffer: the buffer to allocate for.
+ *
+ * This function is used in conjunction with ring_buffer_read_page.
+ * When reading a full page from the ring buffer, these functions
+ * can be used to speed up the process. The calling function should
+ * allocate a few pages first with this function. Then when it
+ * needs to get pages from the ring buffer, it passes the result
+ * of this function into ring_buffer_read_page, which will swap
+ * the page that was allocated, with the read page of the buffer.
+ *
+ * Returns:
+ *  The page allocated, or NULL on error.
+ */
+void *ring_buffer_alloc_read_page(struct ring_buffer *buffer)
+{
+        unsigned long addr;
+        struct buffer_data_page *bpage;
+
+        addr = __get_free_page(GFP_KERNEL);
+        if (!addr)
+                return NULL;
+
+        bpage = (void *)addr;
+
+        return bpage;
+}
+
+/**
+ * ring_buffer_free_read_page - free an allocated read page
+ * @buffer: the buffer the page was allocate for
+ * @data: the page to free
+ *
+ * Free a page allocated from ring_buffer_alloc_read_page.
+ */
+void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data)
+{
+        free_page((unsigned long)data);
+}
+
+/**
+ * ring_buffer_read_page - extract a page from the ring buffer
+ * @buffer: buffer to extract from
+ * @data_page: the page to use allocated from ring_buffer_alloc_read_page
+ * @cpu: the cpu of the buffer to extract
+ * @full: should the extraction only happen when the page is full.
+ *
+ * This function will pull out a page from the ring buffer and consume it.
+ * @data_page must be the address of the variable that was returned
+ * from ring_buffer_alloc_read_page. This is because the page might be used
+ * to swap with a page in the ring buffer.
+ *
+ * for example:
+ *      rpage = ring_buffer_alloc_page(buffer);
+ *      if (!rpage)
+ *              return error;
+ *      ret = ring_buffer_read_page(buffer, &rpage, cpu, 0);
+ *      if (ret)
+ *              process_page(rpage);
+ *
+ * When @full is set, the function will not return true unless
+ * the writer is off the reader page.
+ *
+ * Note: it is up to the calling functions to handle sleeps and wakeups.
+ *  The ring buffer can be used anywhere in the kernel and can not
+ *  blindly call wake_up. The layer that uses the ring buffer must be
+ *  responsible for that.
+ *
+ * Returns:
+ *  1 if data has been transferred
+ *  0 if no data has been transferred.
+ */
+int ring_buffer_read_page(struct ring_buffer *buffer,
+                            void **data_page, int cpu, int full)
+{
+        struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
+        struct ring_buffer_event *event;
+        struct buffer_data_page *bpage;
+        unsigned long flags;
+        int ret = 0;
+
+        if (!data_page)
+                return 0;
+
+        bpage = *data_page;
+        if (!bpage)
+                return 0;
+
+        spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+
+        /*
+         * rb_buffer_peek will get the next ring buffer if
+         * the current reader page is empty.
+         */
+        event = rb_buffer_peek(buffer, cpu, NULL);
+        if (!event)
+                goto out;
+
+        /* check for data */
+        if (!local_read(&cpu_buffer->reader_page->page->commit))
+                goto out;
+        /*
+         * If the writer is already off of the read page, then simply
+         * switch the read page with the given page. Otherwise
+         * we need to copy the data from the reader to the writer.
+         */
+        if (cpu_buffer->reader_page == cpu_buffer->commit_page) {
+                unsigned int read = cpu_buffer->reader_page->read;
+
+                if (full)
+                        goto out;
+                /* The writer is still on the reader page, we must copy */
+                bpage = cpu_buffer->reader_page->page;
+                memcpy(bpage->data,
+                       cpu_buffer->reader_page->page->data + read,
+                       local_read(&bpage->commit) - read);
+
+                /* consume what was read */
+                cpu_buffer->reader_page += read;
+
+        } else {
+                /* swap the pages */
+                rb_init_page(bpage);
+                bpage = cpu_buffer->reader_page->page;
+                cpu_buffer->reader_page->page = *data_page;
+                cpu_buffer->reader_page->read = 0;
+                *data_page = bpage;
+        }
+        ret = 1;
+
+        /* update the entry counter */
+        rb_remove_entries(cpu_buffer, bpage);
+ out:
+        spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+
+        return ret;
+}
+
+static ssize_t
+rb_simple_read(struct file *filp, char __user *ubuf,
+               size_t cnt, loff_t *ppos)
+{
+        long *p = filp->private_data;
+        char buf[64];
+        int r;
+
+        if (test_bit(RB_BUFFERS_DISABLED_BIT, p))
+                r = sprintf(buf, "permanently disabled\n");
+        else
+                r = sprintf(buf, "%d\n", test_bit(RB_BUFFERS_ON_BIT, p));
+
+        return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
+}
+
+static ssize_t
+rb_simple_write(struct file *filp, const char __user *ubuf,
+                size_t cnt, loff_t *ppos)
+{
+        long *p = filp->private_data;
+        char buf[64];
+        long val;
+        int ret;
+
+        if (cnt >= sizeof(buf))
+                return -EINVAL;
+
+        if (copy_from_user(&buf, ubuf, cnt))
+                return -EFAULT;
+
+        buf[cnt] = 0;
+
+        ret = strict_strtoul(buf, 10, &val);
+        if (ret < 0)
+                return ret;
+
+        if (val)
+                set_bit(RB_BUFFERS_ON_BIT, p);
+        else
+                clear_bit(RB_BUFFERS_ON_BIT, p);
+
+        (*ppos)++;
+
+        return cnt;
+}
+
+static struct file_operations rb_simple_fops = {
+        .open           = tracing_open_generic,
+        .read           = rb_simple_read,
+        .write          = rb_simple_write,
+};
+
+
+static __init int rb_init_debugfs(void)
+{
+        struct dentry *d_tracer;
+        struct dentry *entry;
+
+        d_tracer = tracing_init_dentry();
+
+        entry = debugfs_create_file("tracing_on", 0644, d_tracer,
+                                    &ring_buffer_flags, &rb_simple_fops);
+        if (!entry)
+                pr_warning("Could not create debugfs 'tracing_on' entry\n");
+
+        return 0;
+}
+
+fs_initcall(rb_init_debugfs);