1 files changed, 254 insertions, 133 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 63dbc7ff213f..5c75deeefe30 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -43,9 +43,6 @@
 
 #define TRACE_BUFFER_FLAGS      (RB_FL_OVERWRITE)
 
-unsigned long __read_mostly     tracing_max_latency;
-unsigned long __read_mostly     tracing_thresh;
-
 /*
  * On boot up, the ring buffer is set to the minimum size, so that
  * we do not waste memory on systems that are not using tracing.
@@ -172,10 +169,11 @@ static struct trace_array	global_trace;
 
 static DEFINE_PER_CPU(struct trace_array_cpu, global_trace_cpu);
 
-int filter_current_check_discard(struct ftrace_event_call *call, void *rec,
+int filter_current_check_discard(struct ring_buffer *buffer,
+                                 struct ftrace_event_call *call, void *rec,
                                  struct ring_buffer_event *event)
 {
-        return filter_check_discard(call, rec, global_trace.buffer, event);
+        return filter_check_discard(call, rec, buffer, event);
 }
 EXPORT_SYMBOL_GPL(filter_current_check_discard);
 
@@ -266,6 +264,9 @@ unsigned long trace_flags = TRACE_ITER_PRINT_PARENT | TRACE_ITER_PRINTK |
         TRACE_ITER_ANNOTATE | TRACE_ITER_CONTEXT_INFO | TRACE_ITER_SLEEP_TIME |
         TRACE_ITER_GRAPH_TIME;
 
+static int trace_stop_count;
+static DEFINE_SPINLOCK(tracing_start_lock);
+
 /**
  * trace_wake_up - wake up tasks waiting for trace input
  *
@@ -338,45 +339,6 @@ static struct {
 
 int trace_clock_id;
 
-/*
- * ftrace_max_lock is used to protect the swapping of buffers
- * when taking a max snapshot. The buffers themselves are
- * protected by per_cpu spinlocks. But the action of the swap
- * needs its own lock.
- *
- * This is defined as a raw_spinlock_t in order to help
- * with performance when lockdep debugging is enabled.
- */
-static raw_spinlock_t ftrace_max_lock =
-        (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
-
-/*
- * Copy the new maximum trace into the separate maximum-trace
- * structure. (this way the maximum trace is permanently saved,
- * for later retrieval via /sys/kernel/debug/tracing/latency_trace)
- */
-static void
-__update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
-{
-        struct trace_array_cpu *data = tr->data[cpu];
-
-        max_tr.cpu = cpu;
-        max_tr.time_start = data->preempt_timestamp;
-
-        data = max_tr.data[cpu];
-        data->saved_latency = tracing_max_latency;
-
-        memcpy(data->comm, tsk->comm, TASK_COMM_LEN);
-        data->pid = tsk->pid;
-        data->uid = task_uid(tsk);
-        data->nice = tsk->static_prio - 20 - MAX_RT_PRIO;
-        data->policy = tsk->policy;
-        data->rt_priority = tsk->rt_priority;
-
-        /* record this tasks comm */
-        tracing_record_cmdline(tsk);
-}
-
 ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf, size_t cnt)
 {
         int len;
@@ -420,6 +382,56 @@ static ssize_t trace_seq_to_buffer(struct trace_seq *s, void *buf, size_t cnt)
         return cnt;
 }
 
+/*
+ * ftrace_max_lock is used to protect the swapping of buffers
+ * when taking a max snapshot. The buffers themselves are
+ * protected by per_cpu spinlocks. But the action of the swap
+ * needs its own lock.
+ *
+ * This is defined as a raw_spinlock_t in order to help
+ * with performance when lockdep debugging is enabled.
+ *
+ * It is also used in other places outside the update_max_tr
+ * so it needs to be defined outside of the
+ * CONFIG_TRACER_MAX_TRACE.
+ */
+static raw_spinlock_t ftrace_max_lock =
+        (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
+
+#ifdef CONFIG_TRACER_MAX_TRACE
+unsigned long __read_mostly     tracing_max_latency;
+unsigned long __read_mostly     tracing_thresh;
+
+/*
+ * Copy the new maximum trace into the separate maximum-trace
+ * structure. (this way the maximum trace is permanently saved,
+ * for later retrieval via /sys/kernel/debug/tracing/latency_trace)
+ */
+static void
+__update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
+{
+        struct trace_array_cpu *data = tr->data[cpu];
+        struct trace_array_cpu *max_data = tr->data[cpu];
+
+        max_tr.cpu = cpu;
+        max_tr.time_start = data->preempt_timestamp;
+
+        max_data = max_tr.data[cpu];
+        max_data->saved_latency = tracing_max_latency;
+        max_data->critical_start = data->critical_start;
+        max_data->critical_end = data->critical_end;
+
+        memcpy(data->comm, tsk->comm, TASK_COMM_LEN);
+        max_data->pid = tsk->pid;
+        max_data->uid = task_uid(tsk);
+        max_data->nice = tsk->static_prio - 20 - MAX_RT_PRIO;
+        max_data->policy = tsk->policy;
+        max_data->rt_priority = tsk->rt_priority;
+
+        /* record this tasks comm */
+        tracing_record_cmdline(tsk);
+}
+
 /**
  * update_max_tr - snapshot all trace buffers from global_trace to max_tr
  * @tr: tracer
@@ -434,16 +446,15 @@ update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
 {
         struct ring_buffer *buf = tr->buffer;
 
+        if (trace_stop_count)
+                return;
+
         WARN_ON_ONCE(!irqs_disabled());
         __raw_spin_lock(&ftrace_max_lock);
 
         tr->buffer = max_tr.buffer;
         max_tr.buffer = buf;
 
-        ftrace_disable_cpu();
-        ring_buffer_reset(tr->buffer);
-        ftrace_enable_cpu();
-
         __update_max_tr(tr, tsk, cpu);
         __raw_spin_unlock(&ftrace_max_lock);
 }
@@ -461,21 +472,35 @@ update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu)
 {
         int ret;
 
+        if (trace_stop_count)
+                return;
+
         WARN_ON_ONCE(!irqs_disabled());
         __raw_spin_lock(&ftrace_max_lock);
 
         ftrace_disable_cpu();
 
-        ring_buffer_reset(max_tr.buffer);
         ret = ring_buffer_swap_cpu(max_tr.buffer, tr->buffer, cpu);
 
+        if (ret == -EBUSY) {
+                /*
+                 * We failed to swap the buffer due to a commit taking
+                 * place on this CPU. We fail to record, but we reset
+                 * the max trace buffer (no one writes directly to it)
+                 * and flag that it failed.
+                 */
+                trace_array_printk(&max_tr, _THIS_IP_,
+                        "Failed to swap buffers due to commit in progress\n");
+        }
+
         ftrace_enable_cpu();
 
-        WARN_ON_ONCE(ret && ret != -EAGAIN);
+        WARN_ON_ONCE(ret && ret != -EAGAIN && ret != -EBUSY);
 
         __update_max_tr(tr, tsk, cpu);
         __raw_spin_unlock(&ftrace_max_lock);
 }
+#endif /* CONFIG_TRACER_MAX_TRACE */
 
 /**
  * register_tracer - register a tracer with the ftrace system.
@@ -532,7 +557,6 @@ __acquires(kernel_lock)
         if (type->selftest && !tracing_selftest_disabled) {
                 struct tracer *saved_tracer = current_trace;
                 struct trace_array *tr = &global_trace;
-                int i;
 
                 /*
                  * Run a selftest on this tracer.
@@ -541,8 +565,7 @@ __acquires(kernel_lock)
                  * internal tracing to verify that everything is in order.
                  * If we fail, we do not register this tracer.
                  */
-                for_each_tracing_cpu(i)
-                        tracing_reset(tr, i);
+                tracing_reset_online_cpus(tr);
 
                 current_trace = type;
                 /* the test is responsible for initializing and enabling */
@@ -555,8 +578,7 @@ __acquires(kernel_lock)
                         goto out;
                 }
                 /* Only reset on passing, to avoid touching corrupted buffers */
-                for_each_tracing_cpu(i)
-                        tracing_reset(tr, i);
+                tracing_reset_online_cpus(tr);
 
                 printk(KERN_CONT "PASSED\n");
         }
@@ -631,21 +653,42 @@ void unregister_tracer(struct tracer *type)
         mutex_unlock(&trace_types_lock);
 }
 
-void tracing_reset(struct trace_array *tr, int cpu)
+static void __tracing_reset(struct trace_array *tr, int cpu)
 {
         ftrace_disable_cpu();
         ring_buffer_reset_cpu(tr->buffer, cpu);
         ftrace_enable_cpu();
 }
 
+void tracing_reset(struct trace_array *tr, int cpu)
+{
+        struct ring_buffer *buffer = tr->buffer;
+
+        ring_buffer_record_disable(buffer);
+
+        /* Make sure all commits have finished */
+        synchronize_sched();
+        __tracing_reset(tr, cpu);
+
+        ring_buffer_record_enable(buffer);
+}
+
 void tracing_reset_online_cpus(struct trace_array *tr)
 {
+        struct ring_buffer *buffer = tr->buffer;
         int cpu;
 
+        ring_buffer_record_disable(buffer);
+
+        /* Make sure all commits have finished */
+        synchronize_sched();
+
         tr->time_start = ftrace_now(tr->cpu);
 
         for_each_online_cpu(cpu)
-                tracing_reset(tr, cpu);
+                __tracing_reset(tr, cpu);
+
+        ring_buffer_record_enable(buffer);
 }
 
 void tracing_reset_current(int cpu)
@@ -676,9 +719,6 @@ static void trace_init_cmdlines(void)
         cmdline_idx = 0;
 }
 
-static int trace_stop_count;
-static DEFINE_SPINLOCK(tracing_start_lock);
-
 /**
  * ftrace_off_permanent - disable all ftrace code permanently
  *
@@ -859,14 +899,15 @@ tracing_generic_entry_update(struct trace_entry *entry, unsigned long flags,
 }
 EXPORT_SYMBOL_GPL(tracing_generic_entry_update);
 
-struct ring_buffer_event *trace_buffer_lock_reserve(struct trace_array *tr,
-                                                    int type,
-                                                    unsigned long len,
-                                                    unsigned long flags, int pc)
+struct ring_buffer_event *
+trace_buffer_lock_reserve(struct ring_buffer *buffer,
+                          int type,
+                          unsigned long len,
+                          unsigned long flags, int pc)
 {
         struct ring_buffer_event *event;
 
-        event = ring_buffer_lock_reserve(tr->buffer, len);
+        event = ring_buffer_lock_reserve(buffer, len);
         if (event != NULL) {
                 struct trace_entry *ent = ring_buffer_event_data(event);
 
@@ -877,53 +918,59 @@ struct ring_buffer_event *trace_buffer_lock_reserve(struct trace_array *tr,
         return event;
 }
 
-static inline void __trace_buffer_unlock_commit(struct trace_array *tr,
-                                        struct ring_buffer_event *event,
-                                        unsigned long flags, int pc,
-                                        int wake)
+static inline void
+__trace_buffer_unlock_commit(struct ring_buffer *buffer,
+                             struct ring_buffer_event *event,
+                             unsigned long flags, int pc,
+                             int wake)
 {
-        ring_buffer_unlock_commit(tr->buffer, event);
+        ring_buffer_unlock_commit(buffer, event);
 
-        ftrace_trace_stack(tr, flags, 6, pc);
-        ftrace_trace_userstack(tr, flags, pc);
+        ftrace_trace_stack(buffer, flags, 6, pc);
+        ftrace_trace_userstack(buffer, flags, pc);
 
         if (wake)
                 trace_wake_up();
 }
 
-void trace_buffer_unlock_commit(struct trace_array *tr,
-                                        struct ring_buffer_event *event,
-                                        unsigned long flags, int pc)
+void trace_buffer_unlock_commit(struct ring_buffer *buffer,
+                                struct ring_buffer_event *event,
+                                unsigned long flags, int pc)
 {
-        __trace_buffer_unlock_commit(tr, event, flags, pc, 1);
+        __trace_buffer_unlock_commit(buffer, event, flags, pc, 1);
 }
 
 struct ring_buffer_event *
-trace_current_buffer_lock_reserve(int type, unsigned long len,
+trace_current_buffer_lock_reserve(struct ring_buffer **current_rb,
+                                  int type, unsigned long len,
                                   unsigned long flags, int pc)
 {
-        return trace_buffer_lock_reserve(&global_trace,
+        *current_rb = global_trace.buffer;
+        return trace_buffer_lock_reserve(*current_rb,
                                          type, len, flags, pc);
 }
 EXPORT_SYMBOL_GPL(trace_current_buffer_lock_reserve);
 
-void trace_current_buffer_unlock_commit(struct ring_buffer_event *event,
+void trace_current_buffer_unlock_commit(struct ring_buffer *buffer,
+                                        struct ring_buffer_event *event,
                                         unsigned long flags, int pc)
 {
-        __trace_buffer_unlock_commit(&global_trace, event, flags, pc, 1);
+        __trace_buffer_unlock_commit(buffer, event, flags, pc, 1);
 }
 EXPORT_SYMBOL_GPL(trace_current_buffer_unlock_commit);
 
-void trace_nowake_buffer_unlock_commit(struct ring_buffer_event *event,
-                                        unsigned long flags, int pc)
+void trace_nowake_buffer_unlock_commit(struct ring_buffer *buffer,
+                                       struct ring_buffer_event *event,
+                                       unsigned long flags, int pc)
 {
-        __trace_buffer_unlock_commit(&global_trace, event, flags, pc, 0);
+        __trace_buffer_unlock_commit(buffer, event, flags, pc, 0);
 }
 EXPORT_SYMBOL_GPL(trace_nowake_buffer_unlock_commit);
 
-void trace_current_buffer_discard_commit(struct ring_buffer_event *event)
+void trace_current_buffer_discard_commit(struct ring_buffer *buffer,
+                                         struct ring_buffer_event *event)
 {
-        ring_buffer_discard_commit(global_trace.buffer, event);
+        ring_buffer_discard_commit(buffer, event);
 }
 EXPORT_SYMBOL_GPL(trace_current_buffer_discard_commit);
 
@@ -933,6 +980,7 @@ trace_function(struct trace_array *tr,
                int pc)
 {
         struct ftrace_event_call *call = &event_function;
+        struct ring_buffer *buffer = tr->buffer;
         struct ring_buffer_event *event;
         struct ftrace_entry *entry;
 
@@ -940,7 +988,7 @@ trace_function(struct trace_array *tr,
         if (unlikely(local_read(&__get_cpu_var(ftrace_cpu_disabled))))
                 return;
 
-        event = trace_buffer_lock_reserve(tr, TRACE_FN, sizeof(*entry),
+        event = trace_buffer_lock_reserve(buffer, TRACE_FN, sizeof(*entry),
                                           flags, pc);
         if (!event)
                 return;
@@ -948,8 +996,8 @@ trace_function(struct trace_array *tr,
         entry->ip                       = ip;
         entry->parent_ip                = parent_ip;
 
-        if (!filter_check_discard(call, entry, tr->buffer, event))
-                ring_buffer_unlock_commit(tr->buffer, event);
+        if (!filter_check_discard(call, entry, buffer, event))
+                ring_buffer_unlock_commit(buffer, event);
 }
 
 void
@@ -962,7 +1010,7 @@ ftrace(struct trace_array *tr, struct trace_array_cpu *data,
 }
 
 #ifdef CONFIG_STACKTRACE
-static void __ftrace_trace_stack(struct trace_array *tr,
+static void __ftrace_trace_stack(struct ring_buffer *buffer,
                                  unsigned long flags,
                                  int skip, int pc)
 {
@@ -971,7 +1019,7 @@ static void __ftrace_trace_stack(struct trace_array *tr,
         struct stack_entry *entry;
         struct stack_trace trace;
 
-        event = trace_buffer_lock_reserve(tr, TRACE_STACK,
+        event = trace_buffer_lock_reserve(buffer, TRACE_STACK,
                                           sizeof(*entry), flags, pc);
         if (!event)
                 return;
@@ -984,26 +1032,27 @@ static void __ftrace_trace_stack(struct trace_array *tr,
         trace.entries           = entry->caller;
 
         save_stack_trace(&trace);
-        if (!filter_check_discard(call, entry, tr->buffer, event))
-                ring_buffer_unlock_commit(tr->buffer, event);
+        if (!filter_check_discard(call, entry, buffer, event))
+                ring_buffer_unlock_commit(buffer, event);
 }
 
-void ftrace_trace_stack(struct trace_array *tr, unsigned long flags, int skip,
-                        int pc)
+void ftrace_trace_stack(struct ring_buffer *buffer, unsigned long flags,
+                        int skip, int pc)
 {
         if (!(trace_flags & TRACE_ITER_STACKTRACE))
                 return;
 
-        __ftrace_trace_stack(tr, flags, skip, pc);
+        __ftrace_trace_stack(buffer, flags, skip, pc);
 }
 
 void __trace_stack(struct trace_array *tr, unsigned long flags, int skip,
                    int pc)
 {
-        __ftrace_trace_stack(tr, flags, skip, pc);
+        __ftrace_trace_stack(tr->buffer, flags, skip, pc);
 }
 
-void ftrace_trace_userstack(struct trace_array *tr, unsigned long flags, int pc)
+void
+ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags, int pc)
 {
         struct ftrace_event_call *call = &event_user_stack;
         struct ring_buffer_event *event;
@@ -1013,7 +1062,7 @@ void ftrace_trace_userstack(struct trace_array *tr, unsigned long flags, int pc)
         if (!(trace_flags & TRACE_ITER_USERSTACKTRACE))
                 return;
 
-        event = trace_buffer_lock_reserve(tr, TRACE_USER_STACK,
+        event = trace_buffer_lock_reserve(buffer, TRACE_USER_STACK,
                                           sizeof(*entry), flags, pc);
         if (!event)
                 return;
@@ -1027,8 +1076,8 @@ void ftrace_trace_userstack(struct trace_array *tr, unsigned long flags, int pc)
         trace.entries           = entry->caller;
 
         save_stack_trace_user(&trace);
-        if (!filter_check_discard(call, entry, tr->buffer, event))
-                ring_buffer_unlock_commit(tr->buffer, event);
+        if (!filter_check_discard(call, entry, buffer, event))
+                ring_buffer_unlock_commit(buffer, event);
 }
 
 #ifdef UNUSED
@@ -1047,9 +1096,10 @@ ftrace_trace_special(void *__tr,
 {
         struct ring_buffer_event *event;
         struct trace_array *tr = __tr;
+        struct ring_buffer *buffer = tr->buffer;
         struct special_entry *entry;
 
-        event = trace_buffer_lock_reserve(tr, TRACE_SPECIAL,
+        event = trace_buffer_lock_reserve(buffer, TRACE_SPECIAL,
                                           sizeof(*entry), 0, pc);
         if (!event)
                 return;
@@ -1057,7 +1107,7 @@ ftrace_trace_special(void *__tr,
         entry->arg1                     = arg1;
         entry->arg2                     = arg2;
         entry->arg3                     = arg3;
-        trace_buffer_unlock_commit(tr, event, 0, pc);
+        trace_buffer_unlock_commit(buffer, event, 0, pc);
 }
 
 void
@@ -1103,6 +1153,7 @@ int trace_vbprintk(unsigned long ip, const char *fmt, va_list args)
 
         struct ftrace_event_call *call = &event_bprint;
         struct ring_buffer_event *event;
+        struct ring_buffer *buffer;
         struct trace_array *tr = &global_trace;
         struct trace_array_cpu *data;
         struct bprint_entry *entry;
@@ -1135,7 +1186,9 @@ int trace_vbprintk(unsigned long ip, const char *fmt, va_list args)
                 goto out_unlock;
 
         size = sizeof(*entry) + sizeof(u32) * len;
-        event = trace_buffer_lock_reserve(tr, TRACE_BPRINT, size, flags, pc);
+        buffer = tr->buffer;
+        event = trace_buffer_lock_reserve(buffer, TRACE_BPRINT, size,
+                                          flags, pc);
         if (!event)
                 goto out_unlock;
         entry = ring_buffer_event_data(event);
@@ -1143,8 +1196,8 @@ int trace_vbprintk(unsigned long ip, const char *fmt, va_list args)
         entry->fmt                      = fmt;
 
         memcpy(entry->buf, trace_buf, sizeof(u32) * len);
-        if (!filter_check_discard(call, entry, tr->buffer, event))
-                ring_buffer_unlock_commit(tr->buffer, event);
+        if (!filter_check_discard(call, entry, buffer, event))
+                ring_buffer_unlock_commit(buffer, event);
 
 out_unlock:
         __raw_spin_unlock(&trace_buf_lock);
@@ -1159,14 +1212,30 @@ out:
 }
 EXPORT_SYMBOL_GPL(trace_vbprintk);
 
-int trace_vprintk(unsigned long ip, const char *fmt, va_list args)
+int trace_array_printk(struct trace_array *tr,
+                       unsigned long ip, const char *fmt, ...)
+{
+        int ret;
+        va_list ap;
+
+        if (!(trace_flags & TRACE_ITER_PRINTK))
+                return 0;
+
+        va_start(ap, fmt);
+        ret = trace_array_vprintk(tr, ip, fmt, ap);
+        va_end(ap);
+        return ret;
+}
+
+int trace_array_vprintk(struct trace_array *tr,
+                        unsigned long ip, const char *fmt, va_list args)
 {
         static raw_spinlock_t trace_buf_lock = __RAW_SPIN_LOCK_UNLOCKED;
         static char trace_buf[TRACE_BUF_SIZE];
 
         struct ftrace_event_call *call = &event_print;
         struct ring_buffer_event *event;
-        struct trace_array *tr = &global_trace;
+        struct ring_buffer *buffer;
         struct trace_array_cpu *data;
         int cpu, len = 0, size, pc;
         struct print_entry *entry;
@@ -1194,7 +1263,9 @@ int trace_vprintk(unsigned long ip, const char *fmt, va_list args)
         trace_buf[len] = 0;
 
         size = sizeof(*entry) + len + 1;
-        event = trace_buffer_lock_reserve(tr, TRACE_PRINT, size, irq_flags, pc);
+        buffer = tr->buffer;
+        event = trace_buffer_lock_reserve(buffer, TRACE_PRINT, size,
+                                          irq_flags, pc);
         if (!event)
                 goto out_unlock;
         entry = ring_buffer_event_data(event);
@@ -1202,8 +1273,8 @@ int trace_vprintk(unsigned long ip, const char *fmt, va_list args)
 
         memcpy(&entry->buf, trace_buf, len);
         entry->buf[len] = 0;
-        if (!filter_check_discard(call, entry, tr->buffer, event))
-                ring_buffer_unlock_commit(tr->buffer, event);
+        if (!filter_check_discard(call, entry, buffer, event))
+                ring_buffer_unlock_commit(buffer, event);
 
  out_unlock:
         __raw_spin_unlock(&trace_buf_lock);
@@ -1215,6 +1286,11 @@ int trace_vprintk(unsigned long ip, const char *fmt, va_list args)
 
         return len;
 }
+
+int trace_vprintk(unsigned long ip, const char *fmt, va_list args)
+{
+        return trace_array_printk(&global_trace, ip, fmt, args);
+}
 EXPORT_SYMBOL_GPL(trace_vprintk);
 
 enum trace_file_type {
@@ -1354,6 +1430,37 @@ static void *s_next(struct seq_file *m, void *v, loff_t *pos)
         return ent;
 }
 
+static void tracing_iter_reset(struct trace_iterator *iter, int cpu)
+{
+        struct trace_array *tr = iter->tr;
+        struct ring_buffer_event *event;
+        struct ring_buffer_iter *buf_iter;
+        unsigned long entries = 0;
+        u64 ts;
+
+        tr->data[cpu]->skipped_entries = 0;
+
+        if (!iter->buffer_iter[cpu])
+                return;
+
+        buf_iter = iter->buffer_iter[cpu];
+        ring_buffer_iter_reset(buf_iter);
+
+        /*
+         * We could have the case with the max latency tracers
+         * that a reset never took place on a cpu. This is evident
+         * by the timestamp being before the start of the buffer.
+         */
+        while ((event = ring_buffer_iter_peek(buf_iter, &ts))) {
+                if (ts >= iter->tr->time_start)
+                        break;
+                entries++;
+                ring_buffer_read(buf_iter, NULL);
+        }
+
+        tr->data[cpu]->skipped_entries = entries;
+}
+
 /*
  * No necessary locking here. The worst thing which can
  * happen is loosing events consumed at the same time
@@ -1392,10 +1499,9 @@ static void *s_start(struct seq_file *m, loff_t *pos)
 
                 if (cpu_file == TRACE_PIPE_ALL_CPU) {
                         for_each_tracing_cpu(cpu)
-                                ring_buffer_iter_reset(iter->buffer_iter[cpu]);
+                                tracing_iter_reset(iter, cpu);
                 } else
-                        ring_buffer_iter_reset(iter->buffer_iter[cpu_file]);
-
+                        tracing_iter_reset(iter, cpu_file);
 
                 ftrace_enable_cpu();
 
@@ -1444,16 +1550,32 @@ print_trace_header(struct seq_file *m, struct trace_iterator *iter)
         struct trace_array *tr = iter->tr;
         struct trace_array_cpu *data = tr->data[tr->cpu];
         struct tracer *type = current_trace;
-        unsigned long total;
-        unsigned long entries;
+        unsigned long entries = 0;
+        unsigned long total = 0;
+        unsigned long count;
         const char *name = "preemption";
+        int cpu;
 
         if (type)
                 name = type->name;
 
-        entries = ring_buffer_entries(iter->tr->buffer);
-        total = entries +
-                ring_buffer_overruns(iter->tr->buffer);
+
+        for_each_tracing_cpu(cpu) {
+                count = ring_buffer_entries_cpu(tr->buffer, cpu);
+                /*
+                 * If this buffer has skipped entries, then we hold all
+                 * entries for the trace and we need to ignore the
+                 * ones before the time stamp.
+                 */
+                if (tr->data[cpu]->skipped_entries) {
+                        count -= tr->data[cpu]->skipped_entries;
+                        /* total is the same as the entries */
+                        total += count;
+                } else
+                        total += count +
+                                ring_buffer_overrun_cpu(tr->buffer, cpu);
+                entries += count;
+        }
 
         seq_printf(m, "# %s latency trace v1.1.5 on %s\n",
                    name, UTS_RELEASE);
@@ -1495,7 +1617,7 @@ print_trace_header(struct seq_file *m, struct trace_iterator *iter)
                 seq_puts(m, "\n#  => ended at:   ");
                 seq_print_ip_sym(&iter->seq, data->critical_end, sym_flags);
                 trace_print_seq(m, &iter->seq);
-                seq_puts(m, "#\n");
+                seq_puts(m, "\n#\n");
         }
 
         seq_puts(m, "#\n");
@@ -1514,6 +1636,9 @@ static void test_cpu_buff_start(struct trace_iterator *iter)
         if (cpumask_test_cpu(iter->cpu, iter->started))
                 return;
 
+        if (iter->tr->data[iter->cpu]->skipped_entries)
+                return;
+
         cpumask_set_cpu(iter->cpu, iter->started);
 
         /* Don't print started cpu buffer for the first entry of the trace */
@@ -1776,19 +1901,23 @@ __tracing_open(struct inode *inode, struct file *file)
         if (ring_buffer_overruns(iter->tr->buffer))
                 iter->iter_flags |= TRACE_FILE_ANNOTATE;
 
+        /* stop the trace while dumping */
+        tracing_stop();
+
         if (iter->cpu_file == TRACE_PIPE_ALL_CPU) {
                 for_each_tracing_cpu(cpu) {
 
                         iter->buffer_iter[cpu] =
                                 ring_buffer_read_start(iter->tr->buffer, cpu);
+                        tracing_iter_reset(iter, cpu);
                 }
         } else {
                 cpu = iter->cpu_file;
                 iter->buffer_iter[cpu] =
                                 ring_buffer_read_start(iter->tr->buffer, cpu);
+                tracing_iter_reset(iter, cpu);
         }
 
-        /* TODO stop tracer */
         ret = seq_open(file, &tracer_seq_ops);
         if (ret < 0) {
                 fail_ret = ERR_PTR(ret);
@@ -1798,9 +1927,6 @@ __tracing_open(struct inode *inode, struct file *file)
         m = file->private_data;
         m->private = iter;
 
-        /* stop the trace while dumping */
-        tracing_stop();
-
         mutex_unlock(&trace_types_lock);
 
         return iter;
@@ -1811,6 +1937,7 @@ __tracing_open(struct inode *inode, struct file *file)
                         ring_buffer_read_finish(iter->buffer_iter[cpu]);
         }
         free_cpumask_var(iter->started);
+        tracing_start();
  fail:
         mutex_unlock(&trace_types_lock);
         kfree(iter->trace);
@@ -3774,17 +3901,9 @@ trace_options_core_write(struct file *filp, const char __user *ubuf, size_t cnt,
         if (ret < 0)
                 return ret;
 
-        switch (val) {
-        case 0:
-                trace_flags &= ~(1 << index);
-                break;
-        case 1:
-                trace_flags |= 1 << index;
-                break;
-
-        default:
+        if (val != 0 && val != 1)
                 return -EINVAL;
-        }
+        set_tracer_flags(1 << index, val);
 
         *ppos += cnt;
 
@@ -3952,11 +4071,13 @@ static __init int tracer_init_debugfs(void)
         trace_create_file("current_tracer", 0644, d_tracer,
                         &global_trace, &set_tracer_fops);
 
+#ifdef CONFIG_TRACER_MAX_TRACE
         trace_create_file("tracing_max_latency", 0644, d_tracer,
                         &tracing_max_latency, &tracing_max_lat_fops);
 
         trace_create_file("tracing_thresh", 0644, d_tracer,
                         &tracing_thresh, &tracing_max_lat_fops);
+#endif
 
         trace_create_file("README", 0444, d_tracer,
                         NULL, &tracing_readme_fops);