1 files changed, 190 insertions, 131 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 1e6640f80454..f3dadae83883 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -22,12 +22,13 @@
 #include <linux/hardirq.h>
 #include <linux/kthread.h>
 #include <linux/uaccess.h>
-#include <linux/kprobes.h>
 #include <linux/ftrace.h>
 #include <linux/sysctl.h>
+#include <linux/slab.h>
 #include <linux/ctype.h>
 #include <linux/list.h>
 #include <linux/hash.h>
+#include <linux/rcupdate.h>
 
 #include <trace/events/sched.h>
 
@@ -85,22 +86,22 @@ ftrace_func_t ftrace_trace_function __read_mostly = ftrace_stub;
 ftrace_func_t __ftrace_trace_function __read_mostly = ftrace_stub;
 ftrace_func_t ftrace_pid_function __read_mostly = ftrace_stub;
 
-#ifdef CONFIG_FUNCTION_GRAPH_TRACER
-static int ftrace_set_func(unsigned long *array, int *idx, char *buffer);
-#endif
-
+/*
+ * Traverse the ftrace_list, invoking all entries.  The reason that we
+ * can use rcu_dereference_raw() is that elements removed from this list
+ * are simply leaked, so there is no need to interact with a grace-period
+ * mechanism.  The rcu_dereference_raw() calls are needed to handle
+ * concurrent insertions into the ftrace_list.
+ *
+ * Silly Alpha and silly pointer-speculation compiler optimizations!
+ */
 static void ftrace_list_func(unsigned long ip, unsigned long parent_ip)
 {
-        struct ftrace_ops *op = ftrace_list;
-
-        /* in case someone actually ports this to alpha! */
-        read_barrier_depends();
+        struct ftrace_ops *op = rcu_dereference_raw(ftrace_list); /*see above*/
 
         while (op != &ftrace_list_end) {
-                /* silly alpha */
-                read_barrier_depends();
                 op->func(ip, parent_ip);
-                op = op->next;
+                op = rcu_dereference_raw(op->next); /*see above*/
         };
 }
 
@@ -155,8 +156,7 @@ static int __register_ftrace_function(struct ftrace_ops *ops)
          * the ops->next pointer is valid before another CPU sees
          * the ops pointer included into the ftrace_list.
          */
-        smp_wmb();
-        ftrace_list = ops;
+        rcu_assign_pointer(ftrace_list, ops);
 
         if (ftrace_enabled) {
                 ftrace_func_t func;
@@ -264,6 +264,7 @@ struct ftrace_profile {
         unsigned long                   counter;
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
         unsigned long long              time;
+        unsigned long long              time_squared;
 #endif
 };
 
@@ -366,9 +367,9 @@ static int function_stat_headers(struct seq_file *m)
 {
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
         seq_printf(m, "  Function                               "
-                   "Hit    Time            Avg\n"
+                   "Hit    Time            Avg             s^2\n"
                       "  --------                               "
-                   "---    ----            ---\n");
+                   "---    ----            ---             ---\n");
 #else
         seq_printf(m, "  Function                               Hit\n"
                       "  --------                               ---\n");
@@ -380,11 +381,19 @@ static int function_stat_show(struct seq_file *m, void *v)
 {
         struct ftrace_profile *rec = v;
         char str[KSYM_SYMBOL_LEN];
+        int ret = 0;
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
-        static DEFINE_MUTEX(mutex);
         static struct trace_seq s;
         unsigned long long avg;
+        unsigned long long stddev;
 #endif
+        mutex_lock(&ftrace_profile_lock);
+
+        /* we raced with function_profile_reset() */
+        if (unlikely(rec->counter == 0)) {
+                ret = -EBUSY;
+                goto out;
+        }
 
         kallsyms_lookup(rec->ip, NULL, NULL, NULL, str);
         seq_printf(m, "  %-30.30s  %10lu", str, rec->counter);
@@ -394,17 +403,31 @@ static int function_stat_show(struct seq_file *m, void *v)
         avg = rec->time;
         do_div(avg, rec->counter);
 
-        mutex_lock(&mutex);
+        /* Sample standard deviation (s^2) */
+        if (rec->counter <= 1)
+                stddev = 0;
+        else {
+                stddev = rec->time_squared - rec->counter * avg * avg;
+                /*
+                 * Divide only 1000 for ns^2 -> us^2 conversion.
+                 * trace_print_graph_duration will divide 1000 again.
+                 */
+                do_div(stddev, (rec->counter - 1) * 1000);
+        }
+
         trace_seq_init(&s);
         trace_print_graph_duration(rec->time, &s);
         trace_seq_puts(&s, "    ");
         trace_print_graph_duration(avg, &s);
+        trace_seq_puts(&s, "    ");
+        trace_print_graph_duration(stddev, &s);
         trace_print_seq(m, &s);
-        mutex_unlock(&mutex);
 #endif
         seq_putc(m, '\n');
+out:
+        mutex_unlock(&ftrace_profile_lock);
 
-        return 0;
+        return ret;
 }
 
 static void ftrace_profile_reset(struct ftrace_profile_stat *stat)
@@ -650,6 +673,10 @@ static void profile_graph_return(struct ftrace_graph_ret *trace)
         if (!stat->hash || !ftrace_profile_enabled)
                 goto out;
 
+        /* If the calltime was zero'd ignore it */
+        if (!trace->calltime)
+                goto out;
+
         calltime = trace->rettime - trace->calltime;
 
         if (!(trace_flags & TRACE_ITER_GRAPH_TIME)) {
@@ -668,8 +695,10 @@ static void profile_graph_return(struct ftrace_graph_ret *trace)
         }
 
         rec = ftrace_find_profiled_func(stat, trace->func);
-        if (rec)
+        if (rec) {
                 rec->time += calltime;
+                rec->time_squared += calltime * calltime;
+        }
 
  out:
         local_irq_restore(flags);
@@ -771,6 +800,7 @@ static const struct file_operations ftrace_profile_fops = {
         .open           = tracing_open_generic,
         .read           = ftrace_profile_read,
         .write          = ftrace_profile_write,
+        .llseek         = default_llseek,
 };
 
 /* used to initialize the real stat files */
@@ -855,10 +885,8 @@ enum {
         FTRACE_ENABLE_CALLS             = (1 << 0),
         FTRACE_DISABLE_CALLS            = (1 << 1),
         FTRACE_UPDATE_TRACE_FUNC        = (1 << 2),
-        FTRACE_ENABLE_MCOUNT            = (1 << 3),
-        FTRACE_DISABLE_MCOUNT           = (1 << 4),
-        FTRACE_START_FUNC_RET           = (1 << 5),
-        FTRACE_STOP_FUNC_RET            = (1 << 6),
+        FTRACE_START_FUNC_RET           = (1 << 3),
+        FTRACE_STOP_FUNC_RET            = (1 << 4),
 };
 
 static int ftrace_filtered;
@@ -898,36 +926,6 @@ static struct dyn_ftrace *ftrace_free_records;
                 }                               \
         }
 
-#ifdef CONFIG_KPROBES
-
-static int frozen_record_count;
-
-static inline void freeze_record(struct dyn_ftrace *rec)
-{
-        if (!(rec->flags & FTRACE_FL_FROZEN)) {
-                rec->flags |= FTRACE_FL_FROZEN;
-                frozen_record_count++;
-        }
-}
-
-static inline void unfreeze_record(struct dyn_ftrace *rec)
-{
-        if (rec->flags & FTRACE_FL_FROZEN) {
-                rec->flags &= ~FTRACE_FL_FROZEN;
-                frozen_record_count--;
-        }
-}
-
-static inline int record_frozen(struct dyn_ftrace *rec)
-{
-        return rec->flags & FTRACE_FL_FROZEN;
-}
-#else
-# define freeze_record(rec)                     ({ 0; })
-# define unfreeze_record(rec)                   ({ 0; })
-# define record_frozen(rec)                     ({ 0; })
-#endif /* CONFIG_KPROBES */
-
 static void ftrace_free_rec(struct dyn_ftrace *rec)
 {
         rec->freelist = ftrace_free_records;
@@ -1025,6 +1023,21 @@ static void ftrace_bug(int failed, unsigned long ip)
 }
 
 
+/* Return 1 if the address range is reserved for ftrace */
+int ftrace_text_reserved(void *start, void *end)
+{
+        struct dyn_ftrace *rec;
+        struct ftrace_page *pg;
+
+        do_for_each_ftrace_rec(pg, rec) {
+                if (rec->ip <= (unsigned long)end &&
+                    rec->ip + MCOUNT_INSN_SIZE > (unsigned long)start)
+                        return 1;
+        } while_for_each_ftrace_rec();
+        return 0;
+}
+
+
 static int
 __ftrace_replace_code(struct dyn_ftrace *rec, int enable)
 {
@@ -1076,14 +1089,6 @@ static void ftrace_replace_code(int enable)
                     !(rec->flags & FTRACE_FL_CONVERTED))
                         continue;
 
-                /* ignore updates to this record's mcount site */
-                if (get_kprobe((void *)rec->ip)) {
-                        freeze_record(rec);
-                        continue;
-                } else {
-                        unfreeze_record(rec);
-                }
-
                 failed = __ftrace_replace_code(rec, enable);
                 if (failed) {
                         rec->flags |= FTRACE_FL_FAILED;
@@ -1220,8 +1225,6 @@ static void ftrace_shutdown(int command)
 
 static void ftrace_startup_sysctl(void)
 {
-        int command = FTRACE_ENABLE_MCOUNT;
-
         if (unlikely(ftrace_disabled))
                 return;
 
@@ -1229,23 +1232,17 @@ static void ftrace_startup_sysctl(void)
         saved_ftrace_func = NULL;
         /* ftrace_start_up is true if we want ftrace running */
         if (ftrace_start_up)
-                command |= FTRACE_ENABLE_CALLS;
-
-        ftrace_run_update_code(command);
+                ftrace_run_update_code(FTRACE_ENABLE_CALLS);
 }
 
 static void ftrace_shutdown_sysctl(void)
 {
-        int command = FTRACE_DISABLE_MCOUNT;
-
         if (unlikely(ftrace_disabled))
                 return;
 
         /* ftrace_start_up is true if ftrace is running */
         if (ftrace_start_up)
-                command |= FTRACE_DISABLE_CALLS;
-
-        ftrace_run_update_code(command);
+                ftrace_run_update_code(FTRACE_DISABLE_CALLS);
 }
 
 static cycle_t          ftrace_update_time;
@@ -1362,24 +1359,29 @@ enum {
 #define FTRACE_BUFF_MAX (KSYM_SYMBOL_LEN+4) /* room for wildcards */
 
 struct ftrace_iterator {
-        struct ftrace_page      *pg;
-        int                     hidx;
-        int                     idx;
-        unsigned                flags;
-        struct trace_parser     parser;
+        loff_t                          pos;
+        loff_t                          func_pos;
+        struct ftrace_page              *pg;
+        struct dyn_ftrace               *func;
+        struct ftrace_func_probe        *probe;
+        struct trace_parser             parser;
+        int                             hidx;
+        int                             idx;
+        unsigned                        flags;
 };
 
 static void *
-t_hash_next(struct seq_file *m, void *v, loff_t *pos)
+t_hash_next(struct seq_file *m, loff_t *pos)
 {
         struct ftrace_iterator *iter = m->private;
-        struct hlist_node *hnd = v;
+        struct hlist_node *hnd = NULL;
         struct hlist_head *hhd;
 
-        WARN_ON(!(iter->flags & FTRACE_ITER_HASH));
-
         (*pos)++;
+        iter->pos = *pos;
 
+        if (iter->probe)
+                hnd = &iter->probe->node;
  retry:
         if (iter->hidx >= FTRACE_FUNC_HASHSIZE)
                 return NULL;
@@ -1402,7 +1404,12 @@ t_hash_next(struct seq_file *m, void *v, loff_t *pos)
                 }
         }
 
-        return hnd;
+        if (WARN_ON_ONCE(!hnd))
+                return NULL;
+
+        iter->probe = hlist_entry(hnd, struct ftrace_func_probe, node);
+
+        return iter;
 }
 
 static void *t_hash_start(struct seq_file *m, loff_t *pos)
@@ -1411,26 +1418,32 @@ static void *t_hash_start(struct seq_file *m, loff_t *pos)
         void *p = NULL;
         loff_t l;
 
-        if (!(iter->flags & FTRACE_ITER_HASH))
-                *pos = 0;
-
-        iter->flags |= FTRACE_ITER_HASH;
+        if (iter->func_pos > *pos)
+                return NULL;
 
         iter->hidx = 0;
-        for (l = 0; l <= *pos; ) {
-                p = t_hash_next(m, p, &l);
+        for (l = 0; l <= (*pos - iter->func_pos); ) {
+                p = t_hash_next(m, &l);
                 if (!p)
                         break;
         }
-        return p;
+        if (!p)
+                return NULL;
+
+        /* Only set this if we have an item */
+        iter->flags |= FTRACE_ITER_HASH;
+
+        return iter;
 }
 
-static int t_hash_show(struct seq_file *m, void *v)
+static int
+t_hash_show(struct seq_file *m, struct ftrace_iterator *iter)
 {
         struct ftrace_func_probe *rec;
-        struct hlist_node *hnd = v;
 
-        rec = hlist_entry(hnd, struct ftrace_func_probe, node);
+        rec = iter->probe;
+        if (WARN_ON_ONCE(!rec))
+                return -EIO;
 
         if (rec->ops->print)
                 return rec->ops->print(m, rec->ip, rec->ops, rec->data);
@@ -1451,12 +1464,13 @@ t_next(struct seq_file *m, void *v, loff_t *pos)
         struct dyn_ftrace *rec = NULL;
 
         if (iter->flags & FTRACE_ITER_HASH)
-                return t_hash_next(m, v, pos);
+                return t_hash_next(m, pos);
 
         (*pos)++;
+        iter->pos = *pos;
 
         if (iter->flags & FTRACE_ITER_PRINTALL)
-                return NULL;
+                return t_hash_start(m, pos);
 
  retry:
         if (iter->idx >= iter->pg->index) {
@@ -1485,7 +1499,20 @@ t_next(struct seq_file *m, void *v, loff_t *pos)
                 }
         }
 
-        return rec;
+        if (!rec)
+                return t_hash_start(m, pos);
+
+        iter->func_pos = *pos;
+        iter->func = rec;
+
+        return iter;
+}
+
+static void reset_iter_read(struct ftrace_iterator *iter)
+{
+        iter->pos = 0;
+        iter->func_pos = 0;
+        iter->flags &= ~(FTRACE_ITER_PRINTALL & FTRACE_ITER_HASH);
 }
 
 static void *t_start(struct seq_file *m, loff_t *pos)
@@ -1496,6 +1523,12 @@ static void *t_start(struct seq_file *m, loff_t *pos)
 
         mutex_lock(&ftrace_lock);
         /*
+         * If an lseek was done, then reset and start from beginning.
+         */
+        if (*pos < iter->pos)
+                reset_iter_read(iter);
+
+        /*
          * For set_ftrace_filter reading, if we have the filter
          * off, we can short cut and just print out that all
          * functions are enabled.
@@ -1504,12 +1537,19 @@ static void *t_start(struct seq_file *m, loff_t *pos)
                 if (*pos > 0)
                         return t_hash_start(m, pos);
                 iter->flags |= FTRACE_ITER_PRINTALL;
+                /* reset in case of seek/pread */
+                iter->flags &= ~FTRACE_ITER_HASH;
                 return iter;
         }
 
         if (iter->flags & FTRACE_ITER_HASH)
                 return t_hash_start(m, pos);
 
+        /*
+         * Unfortunately, we need to restart at ftrace_pages_start
+         * every time we let go of the ftrace_mutex. This is because
+         * those pointers can change without the lock.
+         */
         iter->pg = ftrace_pages_start;
         iter->idx = 0;
         for (l = 0; l <= *pos; ) {
@@ -1518,10 +1558,14 @@ static void *t_start(struct seq_file *m, loff_t *pos)
                         break;
         }
 
-        if (!p && iter->flags & FTRACE_ITER_FILTER)
-                return t_hash_start(m, pos);
+        if (!p) {
+                if (iter->flags & FTRACE_ITER_FILTER)
+                        return t_hash_start(m, pos);
+
+                return NULL;
+        }
 
-        return p;
+        return iter;
 }
 
 static void t_stop(struct seq_file *m, void *p)
@@ -1532,16 +1576,18 @@ 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;
+        struct dyn_ftrace *rec;
 
         if (iter->flags & FTRACE_ITER_HASH)
-                return t_hash_show(m, v);
+                return t_hash_show(m, iter);
 
         if (iter->flags & FTRACE_ITER_PRINTALL) {
                 seq_printf(m, "#### all functions enabled ####\n");
                 return 0;
         }
 
+        rec = iter->func;
+
         if (!rec)
                 return 0;
 
@@ -1593,8 +1639,8 @@ ftrace_failures_open(struct inode *inode, struct file *file)
 
         ret = ftrace_avail_open(inode, file);
         if (!ret) {
-                m = (struct seq_file *)file->private_data;
-                iter = (struct ftrace_iterator *)m->private;
+                m = file->private_data;
+                iter = m->private;
                 iter->flags = FTRACE_ITER_FAILURES;
         }
 
@@ -1884,7 +1930,6 @@ function_trace_probe_call(unsigned long ip, unsigned long parent_ip)
         struct hlist_head *hhd;
         struct hlist_node *n;
         unsigned long key;
-        int resched;
 
         key = hash_long(ip, FTRACE_HASH_BITS);
 
@@ -1898,12 +1943,12 @@ function_trace_probe_call(unsigned long ip, unsigned long parent_ip)
          * period. This syncs the hash iteration and freeing of items
          * on the hash. rcu_read_lock is too dangerous here.
          */
-        resched = ftrace_preempt_disable();
+        preempt_disable_notrace();
         hlist_for_each_entry_rcu(entry, n, hhd, node) {
                 if (entry->ip == ip)
                         entry->ops->func(ip, parent_ip, &entry->data);
         }
-        ftrace_preempt_enable(resched);
+        preempt_enable_notrace();
 }
 
 static struct ftrace_ops trace_probe_ops __read_mostly =
@@ -2300,6 +2345,8 @@ __setup("ftrace_filter=", set_ftrace_filter);
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 static char ftrace_graph_buf[FTRACE_FILTER_SIZE] __initdata;
+static int ftrace_set_func(unsigned long *array, int *idx, char *buffer);
+
 static int __init set_graph_function(char *str)
 {
         strlcpy(ftrace_graph_buf, str, FTRACE_FILTER_SIZE);
@@ -2426,6 +2473,7 @@ static const struct file_operations ftrace_notrace_fops = {
 static DEFINE_MUTEX(graph_lock);
 
 int ftrace_graph_count;
+int ftrace_graph_filter_enabled;
 unsigned long ftrace_graph_funcs[FTRACE_GRAPH_MAX_FUNCS] __read_mostly;
 
 static void *
@@ -2448,7 +2496,7 @@ static void *g_start(struct seq_file *m, loff_t *pos)
         mutex_lock(&graph_lock);
 
         /* Nothing, tell g_show to print all functions are enabled */
-        if (!ftrace_graph_count && !*pos)
+        if (!ftrace_graph_filter_enabled && !*pos)
                 return (void *)1;
 
         return __g_next(m, pos);
@@ -2494,6 +2542,7 @@ ftrace_graph_open(struct inode *inode, struct file *file)
         mutex_lock(&graph_lock);
         if ((file->f_mode & FMODE_WRITE) &&
             (file->f_flags & O_TRUNC)) {
+                ftrace_graph_filter_enabled = 0;
                 ftrace_graph_count = 0;
                 memset(ftrace_graph_funcs, 0, sizeof(ftrace_graph_funcs));
         }
@@ -2519,7 +2568,7 @@ ftrace_set_func(unsigned long *array, int *idx, char *buffer)
         struct dyn_ftrace *rec;
         struct ftrace_page *pg;
         int search_len;
-        int found = 0;
+        int fail = 1;
         int type, not;
         char *search;
         bool exists;
@@ -2530,37 +2579,51 @@ ftrace_set_func(unsigned long *array, int *idx, char *buffer)
 
         /* decode regex */
         type = filter_parse_regex(buffer, strlen(buffer), &search, &not);
-        if (not)
-                return -EINVAL;
+        if (!not && *idx >= FTRACE_GRAPH_MAX_FUNCS)
+                return -EBUSY;
 
         search_len = strlen(search);
 
         mutex_lock(&ftrace_lock);
         do_for_each_ftrace_rec(pg, rec) {
 
-                if (*idx >= FTRACE_GRAPH_MAX_FUNCS)
-                        break;
-
                 if (rec->flags & (FTRACE_FL_FAILED | FTRACE_FL_FREE))
                         continue;
 
                 if (ftrace_match_record(rec, search, search_len, type)) {
-                        /* ensure it is not already in the array */
+                        /* if it is in the array */
                         exists = false;
-                        for (i = 0; i < *idx; i++)
+                        for (i = 0; i < *idx; i++) {
                                 if (array[i] == rec->ip) {
                                         exists = true;
                                         break;
                                 }
-                        if (!exists)
-                                array[(*idx)++] = rec->ip;
-                        found = 1;
+                        }
+
+                        if (!not) {
+                                fail = 0;
+                                if (!exists) {
+                                        array[(*idx)++] = rec->ip;
+                                        if (*idx >= FTRACE_GRAPH_MAX_FUNCS)
+                                                goto out;
+                                }
+                        } else {
+                                if (exists) {
+                                        array[i] = array[--(*idx)];
+                                        array[*idx] = 0;
+                                        fail = 0;
+                                }
+                        }
                 }
         } while_for_each_ftrace_rec();
-
+out:
         mutex_unlock(&ftrace_lock);
 
-        return found ? 0 : -EINVAL;
+        if (fail)
+                return -EINVAL;
+
+        ftrace_graph_filter_enabled = 1;
+        return 0;
 }
 
 static ssize_t
@@ -2570,16 +2633,11 @@ ftrace_graph_write(struct file *file, const char __user *ubuf,
         struct trace_parser parser;
         ssize_t read, ret;
 
-        if (!cnt || cnt < 0)
+        if (!cnt)
                 return 0;
 
         mutex_lock(&graph_lock);
 
-        if (ftrace_graph_count >= FTRACE_GRAPH_MAX_FUNCS) {
-                ret = -EBUSY;
-                goto out_unlock;
-        }
-
         if (trace_parser_get_init(&parser, FTRACE_BUFF_MAX)) {
                 ret = -ENOMEM;
                 goto out_unlock;
@@ -2612,6 +2670,7 @@ static const struct file_operations ftrace_graph_fops = {
         .read           = seq_read,
         .write          = ftrace_graph_write,
         .release        = ftrace_graph_release,
+        .llseek         = seq_lseek,
 };
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
 
@@ -3222,8 +3281,8 @@ free:
 }
 
 static void
-ftrace_graph_probe_sched_switch(struct rq *__rq, struct task_struct *prev,
-                                struct task_struct *next)
+ftrace_graph_probe_sched_switch(void *ignore,
+                        struct task_struct *prev, struct task_struct *next)
 {
         unsigned long long timestamp;
         int index;
@@ -3277,7 +3336,7 @@ static int start_graph_tracing(void)
         } while (ret == -EAGAIN);
 
         if (!ret) {
-                ret = register_trace_sched_switch(ftrace_graph_probe_sched_switch);
+                ret = register_trace_sched_switch(ftrace_graph_probe_sched_switch, NULL);
                 if (ret)
                         pr_info("ftrace_graph: Couldn't activate tracepoint"
                                 " probe to kernel_sched_switch\n");
@@ -3349,11 +3408,11 @@ void unregister_ftrace_graph(void)
                 goto out;
 
         ftrace_graph_active--;
-        unregister_trace_sched_switch(ftrace_graph_probe_sched_switch);
         ftrace_graph_return = (trace_func_graph_ret_t)ftrace_stub;
         ftrace_graph_entry = ftrace_graph_entry_stub;
         ftrace_shutdown(FTRACE_STOP_FUNC_RET);
         unregister_pm_notifier(&ftrace_suspend_notifier);
+        unregister_trace_sched_switch(ftrace_graph_probe_sched_switch, NULL);
 
  out:
         mutex_unlock(&ftrace_lock);
@@ -3364,6 +3423,7 @@ void ftrace_graph_init_task(struct task_struct *t)
 {
         /* Make sure we do not use the parent ret_stack */
         t->ret_stack = NULL;
+        t->curr_ret_stack = -1;
 
         if (ftrace_graph_active) {
                 struct ftrace_ret_stack *ret_stack;
@@ -3373,7 +3433,6 @@ void ftrace_graph_init_task(struct task_struct *t)
                                 GFP_KERNEL);
                 if (!ret_stack)
                         return;
-                t->curr_ret_stack = -1;
                 atomic_set(&t->tracing_graph_pause, 0);
                 atomic_set(&t->trace_overrun, 0);
                 t->ftrace_timestamp = 0;