11 files changed, 260 insertions, 67 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index 35c8ec2ba03a..e5ae36ebe8af 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1127,7 +1127,6 @@ NORET_TYPE void do_exit(long code)
         preempt_disable();
         /* causes final put_task_struct in finish_task_switch(). */
         tsk->state = TASK_DEAD;
-
         schedule();
         BUG();
         /* Avoid "noreturn function does return".  */
diff --git a/kernel/fork.c b/kernel/fork.c
index ac62f43ee430..d6e1a3205f62 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -47,6 +47,7 @@
 #include <linux/mount.h>
 #include <linux/audit.h>
 #include <linux/memcontrol.h>
+#include <linux/ftrace.h>
 #include <linux/profile.h>
 #include <linux/rmap.h>
 #include <linux/acct.h>
@@ -139,6 +140,7 @@ void free_task(struct task_struct *tsk)
         prop_local_destroy_single(&tsk->dirties);
         free_thread_info(tsk->stack);
         rt_mutex_debug_task_free(tsk);
+        ftrace_retfunc_exit_task(tsk);
         free_task_struct(tsk);
 }
 EXPORT_SYMBOL(free_task);
@@ -1269,6 +1271,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
         total_forks++;
         spin_unlock(&current->sighand->siglock);
         write_unlock_irq(&tasklist_lock);
+        ftrace_retfunc_init_task(p);
         proc_fork_connector(p);
         cgroup_post_fork(p);
         return p;
diff --git a/kernel/power/disk.c b/kernel/power/disk.c
index c9d74083746f..f77d3819ef57 100644
--- a/kernel/power/disk.c
+++ b/kernel/power/disk.c
@@ -22,7 +22,6 @@
 #include <linux/console.h>
 #include <linux/cpu.h>
 #include <linux/freezer.h>
-#include <linux/ftrace.h>
 
 #include "power.h"
 
@@ -257,7 +256,7 @@ static int create_image(int platform_mode)
 
 int hibernation_snapshot(int platform_mode)
 {
-        int error, ftrace_save;
+        int error;
 
         /* Free memory before shutting down devices. */
         error = swsusp_shrink_memory();
@@ -269,7 +268,6 @@ int hibernation_snapshot(int platform_mode)
                 goto Close;
 
         suspend_console();
-        ftrace_save = __ftrace_enabled_save();
         error = device_suspend(PMSG_FREEZE);
         if (error)
                 goto Recover_platform;
@@ -299,7 +297,6 @@ int hibernation_snapshot(int platform_mode)
  Resume_devices:
         device_resume(in_suspend ?
                 (error ? PMSG_RECOVER : PMSG_THAW) : PMSG_RESTORE);
-        __ftrace_enabled_restore(ftrace_save);
         resume_console();
  Close:
         platform_end(platform_mode);
@@ -370,11 +367,10 @@ static int resume_target_kernel(void)
 
 int hibernation_restore(int platform_mode)
 {
-        int error, ftrace_save;
+        int error;
 
         pm_prepare_console();
         suspend_console();
-        ftrace_save = __ftrace_enabled_save();
         error = device_suspend(PMSG_QUIESCE);
         if (error)
                 goto Finish;
@@ -389,7 +385,6 @@ int hibernation_restore(int platform_mode)
         platform_restore_cleanup(platform_mode);
         device_resume(PMSG_RECOVER);
  Finish:
-        __ftrace_enabled_restore(ftrace_save);
         resume_console();
         pm_restore_console();
         return error;
@@ -402,7 +397,7 @@ int hibernation_restore(int platform_mode)
 
 int hibernation_platform_enter(void)
 {
-        int error, ftrace_save;
+        int error;
 
         if (!hibernation_ops)
                 return -ENOSYS;
@@ -417,7 +412,6 @@ int hibernation_platform_enter(void)
                 goto Close;
 
         suspend_console();
-        ftrace_save = __ftrace_enabled_save();
         error = device_suspend(PMSG_HIBERNATE);
         if (error) {
                 if (hibernation_ops->recover)
@@ -452,7 +446,6 @@ int hibernation_platform_enter(void)
         hibernation_ops->finish();
  Resume_devices:
         device_resume(PMSG_RESTORE);
-        __ftrace_enabled_restore(ftrace_save);
         resume_console();
  Close:
         hibernation_ops->end();
diff --git a/kernel/power/main.c b/kernel/power/main.c
index b8f7ce9473e8..613f16941b85 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -22,7 +22,6 @@
 #include <linux/freezer.h>
 #include <linux/vmstat.h>
 #include <linux/syscalls.h>
-#include <linux/ftrace.h>
 
 #include "power.h"
 
@@ -317,7 +316,7 @@ static int suspend_enter(suspend_state_t state)
  */
 int suspend_devices_and_enter(suspend_state_t state)
 {
-        int error, ftrace_save;
+        int error;
 
         if (!suspend_ops)
                 return -ENOSYS;
@@ -328,7 +327,6 @@ int suspend_devices_and_enter(suspend_state_t state)
                         goto Close;
         }
         suspend_console();
-        ftrace_save = __ftrace_enabled_save();
         suspend_test_start();
         error = device_suspend(PMSG_SUSPEND);
         if (error) {
@@ -360,7 +358,6 @@ int suspend_devices_and_enter(suspend_state_t state)
         suspend_test_start();
         device_resume(PMSG_RESUME);
         suspend_test_finish("resume devices");
-        __ftrace_enabled_restore(ftrace_save);
         resume_console();
  Close:
         if (suspend_ops->end)
diff --git a/kernel/sched.c b/kernel/sched.c
index 4de56108c86f..388d9db044ab 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5901,6 +5901,7 @@ void __cpuinit init_idle(struct task_struct *idle, int cpu)
          * The idle tasks have their own, simple scheduling class:
          */
         idle->sched_class = &idle_sched_class;
+        ftrace_retfunc_init_task(idle);
 }
 
 /*
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 87fc34a1bb91..9cbf7761f498 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -169,14 +169,29 @@ config TRACE_BRANCH_PROFILING
           This tracer profiles all the the likely and unlikely macros
           in the kernel. It will display the results in:
 
-          /debugfs/tracing/profile_likely
-          /debugfs/tracing/profile_unlikely
+          /debugfs/tracing/profile_annotated_branch
 
           Note: this will add a significant overhead, only turn this
           on if you need to profile the system's use of these macros.
 
           Say N if unsure.
 
+config PROFILE_ALL_BRANCHES
+        bool "Profile all if conditionals"
+        depends on TRACE_BRANCH_PROFILING
+        help
+          This tracer profiles all branch conditions. Every if ()
+          taken in the kernel is recorded whether it hit or miss.
+          The results will be displayed in:
+
+          /debugfs/tracing/profile_branch
+
+          This configuration, when enabled, will impose a great overhead
+          on the system. This should only be enabled when the system
+          is to be analyzed
+
+          Say N if unsure.
+
 config TRACING_BRANCHES
         bool
         help
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index f212da486689..53042f118f23 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1498,10 +1498,77 @@ ftrace_enable_sysctl(struct ctl_table *table, int write,
 
 #ifdef CONFIG_FUNCTION_RET_TRACER
 
+static atomic_t ftrace_retfunc_active;
+
 /* The callback that hooks the return of a function */
 trace_function_return_t ftrace_function_return =
                         (trace_function_return_t)ftrace_stub;
 
+
+/* Try to assign a return stack array on FTRACE_RETSTACK_ALLOC_SIZE tasks. */
+static int alloc_retstack_tasklist(struct ftrace_ret_stack **ret_stack_list)
+{
+        int i;
+        int ret = 0;
+        unsigned long flags;
+        int start = 0, end = FTRACE_RETSTACK_ALLOC_SIZE;
+        struct task_struct *g, *t;
+
+        for (i = 0; i < FTRACE_RETSTACK_ALLOC_SIZE; i++) {
+                ret_stack_list[i] = kmalloc(FTRACE_RETFUNC_DEPTH
+                                        * sizeof(struct ftrace_ret_stack),
+                                        GFP_KERNEL);
+                if (!ret_stack_list[i]) {
+                        start = 0;
+                        end = i;
+                        ret = -ENOMEM;
+                        goto free;
+                }
+        }
+
+        read_lock_irqsave(&tasklist_lock, flags);
+        do_each_thread(g, t) {
+                if (start == end) {
+                        ret = -EAGAIN;
+                        goto unlock;
+                }
+
+                if (t->ret_stack == NULL) {
+                        t->ret_stack = ret_stack_list[start++];
+                        t->curr_ret_stack = -1;
+                        atomic_set(&t->trace_overrun, 0);
+                }
+        } while_each_thread(g, t);
+
+unlock:
+        read_unlock_irqrestore(&tasklist_lock, flags);
+free:
+        for (i = start; i < end; i++)
+                kfree(ret_stack_list[i]);
+        return ret;
+}
+
+/* Allocate a return stack for each task */
+static int start_return_tracing(void)
+{
+        struct ftrace_ret_stack **ret_stack_list;
+        int ret;
+
+        ret_stack_list = kmalloc(FTRACE_RETSTACK_ALLOC_SIZE *
+                                sizeof(struct ftrace_ret_stack *),
+                                GFP_KERNEL);
+
+        if (!ret_stack_list)
+                return -ENOMEM;
+
+        do {
+                ret = alloc_retstack_tasklist(ret_stack_list);
+        } while (ret == -EAGAIN);
+
+        kfree(ret_stack_list);
+        return ret;
+}
+
 int register_ftrace_return(trace_function_return_t func)
 {
         int ret = 0;
@@ -1516,7 +1583,12 @@ int register_ftrace_return(trace_function_return_t func)
                 ret = -EBUSY;
                 goto out;
         }
-
+        atomic_inc(&ftrace_retfunc_active);
+        ret = start_return_tracing();
+        if (ret) {
+                atomic_dec(&ftrace_retfunc_active);
+                goto out;
+        }
         ftrace_tracing_type = FTRACE_TYPE_RETURN;
         ftrace_function_return = func;
         ftrace_startup();
@@ -1530,6 +1602,7 @@ void unregister_ftrace_return(void)
 {
         mutex_lock(&ftrace_sysctl_lock);
 
+        atomic_dec(&ftrace_retfunc_active);
         ftrace_function_return = (trace_function_return_t)ftrace_stub;
         ftrace_shutdown();
         /* Restore normal tracing type */
@@ -1537,6 +1610,32 @@ void unregister_ftrace_return(void)
 
         mutex_unlock(&ftrace_sysctl_lock);
 }
+
+/* Allocate a return stack for newly created task */
+void ftrace_retfunc_init_task(struct task_struct *t)
+{
+        if (atomic_read(&ftrace_retfunc_active)) {
+                t->ret_stack = kmalloc(FTRACE_RETFUNC_DEPTH
+                                * sizeof(struct ftrace_ret_stack),
+                                GFP_KERNEL);
+                if (!t->ret_stack)
+                        return;
+                t->curr_ret_stack = -1;
+                atomic_set(&t->trace_overrun, 0);
+        } else
+                t->ret_stack = NULL;
+}
+
+void ftrace_retfunc_exit_task(struct task_struct *t)
+{
+        struct ftrace_ret_stack *ret_stack = t->ret_stack;
+
+        t->ret_stack = NULL;
+        /* NULL must become visible to IRQs before we free it: */
+        barrier();
+
+        kfree(ret_stack);
+}
 #endif
 
 
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 85ced143c2c4..e206951603c1 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -18,8 +18,46 @@
 
 #include "trace.h"
 
-/* Global flag to disable all recording to ring buffers */
-static int ring_buffers_off __read_mostly;
+/*
+ * 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
@@ -29,7 +67,7 @@ static int ring_buffers_off __read_mostly;
  */
 void tracing_on(void)
 {
-        ring_buffers_off = 0;
+        set_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags);
 }
 
 /**
@@ -42,7 +80,18 @@ void tracing_on(void)
  */
 void tracing_off(void)
 {
-        ring_buffers_off = 1;
+        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"
@@ -1185,7 +1234,7 @@ ring_buffer_lock_reserve(struct ring_buffer *buffer,
         struct ring_buffer_event *event;
         int cpu, resched;
 
-        if (ring_buffers_off)
+        if (ring_buffer_flags != RB_BUFFERS_ON)
                 return NULL;
 
         if (atomic_read(&buffer->record_disabled))
@@ -1297,7 +1346,7 @@ int ring_buffer_write(struct ring_buffer *buffer,
         int ret = -EBUSY;
         int cpu, resched;
 
-        if (ring_buffers_off)
+        if (ring_buffer_flags != RB_BUFFERS_ON)
                 return -EBUSY;
 
         if (atomic_read(&buffer->record_disabled))
@@ -2178,12 +2227,14 @@ static ssize_t
 rb_simple_read(struct file *filp, char __user *ubuf,
                size_t cnt, loff_t *ppos)
 {
-        int *p = filp->private_data;
+        long *p = filp->private_data;
         char buf[64];
         int r;
 
-        /* !ring_buffers_off == tracing_on */
-        r = sprintf(buf, "%d\n", !*p);
+        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);
 }
@@ -2192,7 +2243,7 @@ static ssize_t
 rb_simple_write(struct file *filp, const char __user *ubuf,
                 size_t cnt, loff_t *ppos)
 {
-        int *p = filp->private_data;
+        long *p = filp->private_data;
         char buf[64];
         long val;
         int ret;
@@ -2209,8 +2260,10 @@ rb_simple_write(struct file *filp, const char __user *ubuf,
         if (ret < 0)
                 return ret;
 
-        /* !ring_buffers_off == tracing_on */
-        *p = !val;
+        if (val)
+                set_bit(RB_BUFFERS_ON_BIT, p);
+        else
+                clear_bit(RB_BUFFERS_ON_BIT, p);
 
         (*ppos)++;
 
@@ -2232,7 +2285,7 @@ static __init int rb_init_debugfs(void)
         d_tracer = tracing_init_dentry();
 
         entry = debugfs_create_file("tracing_on", 0644, d_tracer,
-                                    &ring_buffers_off, &rb_simple_fops);
+                                    &ring_buffer_flags, &rb_simple_fops);
         if (!entry)
                 pr_warning("Could not create debugfs 'tracing_on' entry\n");
 
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 48d1536f1ca4..a45b59e53fbc 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -686,6 +686,21 @@ static int trace_stop_count;
 static DEFINE_SPINLOCK(tracing_start_lock);
 
 /**
+ * ftrace_off_permanent - disable all ftrace code permanently
+ *
+ * This should only be called when a serious anomally has
+ * been detected.  This will turn off the function tracing,
+ * ring buffers, and other tracing utilites. It takes no
+ * locks and can be called from any context.
+ */
+void ftrace_off_permanent(void)
+{
+        tracing_disabled = 1;
+        ftrace_stop();
+        tracing_off_permanent();
+}
+
+/**
  * tracing_start - quick start of the tracer
  *
  * If tracing is enabled but was stopped by tracing_stop,
diff --git a/kernel/trace/trace_branch.c b/kernel/trace/trace_branch.c
index 23f9b02ce967..877ee88e6a74 100644
--- a/kernel/trace/trace_branch.c
+++ b/kernel/trace/trace_branch.c
@@ -185,12 +185,13 @@ EXPORT_SYMBOL(ftrace_likely_update);
 struct ftrace_pointer {
         void            *start;
         void            *stop;
+        int             hit;
 };
 
 static void *
 t_next(struct seq_file *m, void *v, loff_t *pos)
 {
-        struct ftrace_pointer *f = m->private;
+        const struct ftrace_pointer *f = m->private;
         struct ftrace_branch_data *p = v;
 
         (*pos)++;
@@ -223,13 +224,17 @@ static void t_stop(struct seq_file *m, void *p)
 
 static int t_show(struct seq_file *m, void *v)
 {
+        const struct ftrace_pointer *fp = m->private;
         struct ftrace_branch_data *p = v;
         const char *f;
-        unsigned long percent;
+        long percent;
 
         if (v == (void *)1) {
-                seq_printf(m, " correct incorrect  %% "
-                              "       Function                "
+                if (fp->hit)
+                        seq_printf(m, "   miss      hit    %% ");
+                else
+                        seq_printf(m, " correct incorrect  %% ");
+                seq_printf(m, "       Function                "
                               "  File              Line\n"
                               " ------- ---------  - "
                               "       --------                "
@@ -243,13 +248,20 @@ static int t_show(struct seq_file *m, void *v)
                 f--;
         f++;
 
+        /*
+         * The miss is overlayed on correct, and hit on incorrect.
+         */
         if (p->correct) {
                 percent = p->incorrect * 100;
                 percent /= p->correct + p->incorrect;
         } else
-                percent = p->incorrect ? 100 : 0;
+                percent = p->incorrect ? 100 : -1;
 
-        seq_printf(m, "%8lu %8lu %3lu ", p->correct, p->incorrect, percent);
+        seq_printf(m, "%8lu %8lu ",  p->correct, p->incorrect);
+        if (percent < 0)
+                seq_printf(m, "  X ");
+        else
+                seq_printf(m, "%3ld ", percent);
         seq_printf(m, "%-30.30s %-20.20s %d\n", p->func, f, p->line);
         return 0;
 }
@@ -261,7 +273,7 @@ static struct seq_operations tracing_likely_seq_ops = {
         .show           = t_show,
 };
 
-static int tracing_likely_open(struct inode *inode, struct file *file)
+static int tracing_branch_open(struct inode *inode, struct file *file)
 {
         int ret;
 
@@ -274,25 +286,30 @@ static int tracing_likely_open(struct inode *inode, struct file *file)
         return ret;
 }
 
-static struct file_operations tracing_likely_fops = {
-        .open           = tracing_likely_open,
+static const struct file_operations tracing_branch_fops = {
+        .open           = tracing_branch_open,
         .read           = seq_read,
         .llseek         = seq_lseek,
 };
 
-extern unsigned long __start_likely_profile[];
-extern unsigned long __stop_likely_profile[];
-extern unsigned long __start_unlikely_profile[];
-extern unsigned long __stop_unlikely_profile[];
+#ifdef CONFIG_PROFILE_ALL_BRANCHES
+extern unsigned long __start_branch_profile[];
+extern unsigned long __stop_branch_profile[];
 
-static struct ftrace_pointer ftrace_likely_pos = {
-        .start                  = __start_likely_profile,
-        .stop                   = __stop_likely_profile,
+static const struct ftrace_pointer ftrace_branch_pos = {
+        .start                  = __start_branch_profile,
+        .stop                   = __stop_branch_profile,
+        .hit                    = 1,
 };
 
-static struct ftrace_pointer ftrace_unlikely_pos = {
-        .start                  = __start_unlikely_profile,
-        .stop                   = __stop_unlikely_profile,
+#endif /* CONFIG_PROFILE_ALL_BRANCHES */
+
+extern unsigned long __start_annotated_branch_profile[];
+extern unsigned long __stop_annotated_branch_profile[];
+
+static const struct ftrace_pointer ftrace_annotated_branch_pos = {
+        .start                  = __start_annotated_branch_profile,
+        .stop                   = __stop_annotated_branch_profile,
 };
 
 static __init int ftrace_branch_init(void)
@@ -302,18 +319,21 @@ static __init int ftrace_branch_init(void)
 
         d_tracer = tracing_init_dentry();
 
-        entry = debugfs_create_file("profile_likely", 0444, d_tracer,
-                                    &ftrace_likely_pos,
-                                    &tracing_likely_fops);
+        entry = debugfs_create_file("profile_annotated_branch", 0444, d_tracer,
+                                    (void *)&ftrace_annotated_branch_pos,
+                                    &tracing_branch_fops);
         if (!entry)
-                pr_warning("Could not create debugfs 'profile_likely' entry\n");
+                pr_warning("Could not create debugfs "
+                           "'profile_annotatet_branch' entry\n");
 
-        entry = debugfs_create_file("profile_unlikely", 0444, d_tracer,
-                                    &ftrace_unlikely_pos,
-                                    &tracing_likely_fops);
+#ifdef CONFIG_PROFILE_ALL_BRANCHES
+        entry = debugfs_create_file("profile_branch", 0444, d_tracer,
+                                    (void *)&ftrace_branch_pos,
+                                    &tracing_branch_fops);
         if (!entry)
                 pr_warning("Could not create debugfs"
-                           " 'profile_unlikely' entry\n");
+                           " 'profile_branch' entry\n");
+#endif
 
         return 0;
 }
diff --git a/kernel/trace/trace_mmiotrace.c b/kernel/trace/trace_mmiotrace.c
index 433d650eda9f..2a98a206acc2 100644
--- a/kernel/trace/trace_mmiotrace.c
+++ b/kernel/trace/trace_mmiotrace.c
@@ -18,12 +18,14 @@ struct header_iter {
 
 static struct trace_array *mmio_trace_array;
 static bool overrun_detected;
+static unsigned long prev_overruns;
 
 static void mmio_reset_data(struct trace_array *tr)
 {
         int cpu;
 
         overrun_detected = false;
+        prev_overruns = 0;
         tr->time_start = ftrace_now(tr->cpu);
 
         for_each_online_cpu(cpu)
@@ -123,16 +125,12 @@ static void mmio_close(struct trace_iterator *iter)
 
 static unsigned long count_overruns(struct trace_iterator *iter)
 {
-        int cpu;
         unsigned long cnt = 0;
-/* FIXME: */
-#if 0
-        for_each_online_cpu(cpu) {
-                cnt += iter->overrun[cpu];
-                iter->overrun[cpu] = 0;
-        }
-#endif
-        (void)cpu;
+        unsigned long over = ring_buffer_overruns(iter->tr->buffer);
+
+        if (over > prev_overruns)
+                cnt = over - prev_overruns;
+        prev_overruns = over;
         return cnt;
 }