4 files changed, 135 insertions, 19 deletions

diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
index 536b0ca46a03..e097c2e6b6dc 100644
--- a/include/linux/ring_buffer.h
+++ b/include/linux/ring_buffer.h
@@ -120,6 +120,9 @@ unsigned long ring_buffer_overruns(struct ring_buffer *buffer);
 u64 ring_buffer_time_stamp(int cpu);
 void ring_buffer_normalize_time_stamp(int cpu, u64 *ts);
 
+void tracing_on(void);
+void tracing_off(void);
+
 enum ring_buffer_flags {
         RB_FL_OVERWRITE         = 1 << 0,
 };
diff --git a/kernel/profile.c b/kernel/profile.c
index 9830a037d8db..5b7d1ac7124c 100644
--- a/kernel/profile.c
+++ b/kernel/profile.c
@@ -544,7 +544,7 @@ static const struct file_operations proc_profile_operations = {
 };
 
 #ifdef CONFIG_SMP
-static void __init profile_nop(void *unused)
+static inline void profile_nop(void *unused)
 {
 }
 
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 4a39d24568c8..e60205722d0c 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -185,7 +185,6 @@ enum {
 };
 
 static int ftrace_filtered;
-static int tracing_on;
 
 static LIST_HEAD(ftrace_new_addrs);
 
@@ -506,13 +505,10 @@ static int __ftrace_modify_code(void *data)
 {
         int *command = data;
 
-        if (*command & FTRACE_ENABLE_CALLS) {
+        if (*command & FTRACE_ENABLE_CALLS)
                 ftrace_replace_code(1);
-                tracing_on = 1;
-        } else if (*command & FTRACE_DISABLE_CALLS) {
+        else if (*command & FTRACE_DISABLE_CALLS)
                 ftrace_replace_code(0);
-                tracing_on = 0;
-        }
 
         if (*command & FTRACE_UPDATE_TRACE_FUNC)
                 ftrace_update_ftrace_func(ftrace_trace_function);
@@ -677,7 +673,7 @@ static int __init ftrace_dyn_table_alloc(unsigned long num_to_init)
 
         cnt = num_to_init / ENTRIES_PER_PAGE;
         pr_info("ftrace: allocating %ld entries in %d pages\n",
-                num_to_init, cnt);
+                num_to_init, cnt + 1);
 
         for (i = 0; i < cnt; i++) {
                 pg->next = (void *)get_zeroed_page(GFP_KERNEL);
@@ -757,13 +753,11 @@ static void *t_start(struct seq_file *m, loff_t *pos)
         void *p = NULL;
         loff_t l = -1;
 
-        if (*pos != iter->pos) {
-                for (p = t_next(m, p, &l); p && l < *pos; p = t_next(m, p, &l))
-                        ;
-        } else {
-                l = *pos;
-                p = t_next(m, p, &l);
-        }
+        if (*pos > iter->pos)
+                *pos = iter->pos;
+
+        l = *pos;
+        p = t_next(m, p, &l);
 
         return p;
 }
@@ -774,15 +768,21 @@ static void t_stop(struct seq_file *m, void *p)
 
 static int t_show(struct seq_file *m, void *v)
 {
+        struct ftrace_iterator *iter = m->private;
         struct dyn_ftrace *rec = v;
         char str[KSYM_SYMBOL_LEN];
+        int ret = 0;
 
         if (!rec)
                 return 0;
 
         kallsyms_lookup(rec->ip, NULL, NULL, NULL, str);
 
-        seq_printf(m, "%s\n", str);
+        ret = seq_printf(m, "%s\n", str);
+        if (ret < 0) {
+                iter->pos--;
+                iter->idx--;
+        }
 
         return 0;
 }
@@ -808,7 +808,7 @@ ftrace_avail_open(struct inode *inode, struct file *file)
                 return -ENOMEM;
 
         iter->pg = ftrace_pages_start;
-        iter->pos = -1;
+        iter->pos = 0;
 
         ret = seq_open(file, &show_ftrace_seq_ops);
         if (!ret) {
@@ -895,7 +895,7 @@ ftrace_regex_open(struct inode *inode, struct file *file, int enable)
 
         if (file->f_mode & FMODE_READ) {
                 iter->pg = ftrace_pages_start;
-                iter->pos = -1;
+                iter->pos = 0;
                 iter->flags = enable ? FTRACE_ITER_FILTER :
                         FTRACE_ITER_NOTRACE;
 
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 2f76193c3489..036456cbb4f7 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -16,14 +16,49 @@
 #include <linux/list.h>
 #include <linux/fs.h>
 
+#include "trace.h"
+
+/* Global flag to disable all recording to ring buffers */
+static int ring_buffers_off __read_mostly;
+
+/**
+ * tracing_on - enable all tracing buffers
+ *
+ * This function enables all tracing buffers that may have been
+ * disabled with tracing_off.
+ */
+void tracing_on(void)
+{
+        ring_buffers_off = 0;
+}
+
+/**
+ * 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)
+{
+        ring_buffers_off = 1;
+}
+
 /* 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)
@@ -503,6 +538,12 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
         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;
@@ -1133,6 +1174,9 @@ ring_buffer_lock_reserve(struct ring_buffer *buffer,
         struct ring_buffer_event *event;
         int cpu, resched;
 
+        if (ring_buffers_off)
+                return NULL;
+
         if (atomic_read(&buffer->record_disabled))
                 return NULL;
 
@@ -1249,6 +1293,9 @@ int ring_buffer_write(struct ring_buffer *buffer,
         int ret = -EBUSY;
         int cpu, resched;
 
+        if (ring_buffers_off)
+                return -EBUSY;
+
         if (atomic_read(&buffer->record_disabled))
                 return -EBUSY;
 
@@ -2070,3 +2117,69 @@ int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
         return 0;
 }
 
+static ssize_t
+rb_simple_read(struct file *filp, char __user *ubuf,
+               size_t cnt, loff_t *ppos)
+{
+        int *p = filp->private_data;
+        char buf[64];
+        int r;
+
+        /* !ring_buffers_off == tracing_on */
+        r = sprintf(buf, "%d\n", !*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)
+{
+        int *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;
+
+        /* !ring_buffers_off == tracing_on */
+        *p = !val;
+
+        (*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_buffers_off, &rb_simple_fops);
+        if (!entry)
+                pr_warning("Could not create debugfs 'tracing_on' entry\n");
+
+        return 0;
+}
+
+fs_initcall(rb_init_debugfs);