1 files changed, 70 insertions, 24 deletions

diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index be682b62fe58..d0871bc0aca5 100644
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c
@@ -10,6 +10,7 @@
 #include <linux/debugfs.h>
 #include <linux/ftrace.h>
 #include <linux/module.h>
+#include <linux/sysctl.h>
 #include <linux/init.h>
 #include <linux/fs.h>
 #include "trace.h"
@@ -31,6 +32,10 @@ static raw_spinlock_t max_stack_lock =
 
 static int stack_trace_disabled __read_mostly;
 static DEFINE_PER_CPU(int, trace_active);
+static DEFINE_MUTEX(stack_sysctl_mutex);
+
+int stack_tracer_enabled;
+static int last_stack_tracer_enabled;
 
 static inline void check_stack(void)
 {
@@ -48,7 +53,7 @@ static inline void check_stack(void)
         if (!object_is_on_stack(&this_size))
                 return;
 
-        raw_local_irq_save(flags);
+        local_irq_save(flags);
         __raw_spin_lock(&max_stack_lock);
 
         /* a race could have already updated it */
@@ -78,6 +83,7 @@ static inline void check_stack(void)
          * on a new max, so it is far from a fast path.
          */
         while (i < max_stack_trace.nr_entries) {
+                int found = 0;
 
                 stack_dump_index[i] = this_size;
                 p = start;
@@ -86,17 +92,19 @@ static inline void check_stack(void)
                         if (*p == stack_dump_trace[i]) {
                                 this_size = stack_dump_index[i++] =
                                         (top - p) * sizeof(unsigned long);
+                                found = 1;
                                 /* Start the search from here */
                                 start = p + 1;
                         }
                 }
 
-                i++;
+                if (!found)
+                        i++;
         }
 
  out:
         __raw_spin_unlock(&max_stack_lock);
-        raw_local_irq_restore(flags);
+        local_irq_restore(flags);
 }
 
 static void
@@ -107,8 +115,7 @@ stack_trace_call(unsigned long ip, unsigned long parent_ip)
         if (unlikely(!ftrace_enabled || stack_trace_disabled))
                 return;
 
-        resched = need_resched();
-        preempt_disable_notrace();
+        resched = ftrace_preempt_disable();
 
         cpu = raw_smp_processor_id();
         /* no atomic needed, we only modify this variable by this cpu */
@@ -120,10 +127,7 @@ stack_trace_call(unsigned long ip, unsigned long parent_ip)
  out:
         per_cpu(trace_active, cpu)--;
         /* prevent recursion in schedule */
-        if (resched)
-                preempt_enable_no_resched_notrace();
-        else
-                preempt_enable_notrace();
+        ftrace_preempt_enable(resched);
 }
 
 static struct ftrace_ops trace_ops __read_mostly =
@@ -166,16 +170,16 @@ stack_max_size_write(struct file *filp, const char __user *ubuf,
         if (ret < 0)
                 return ret;
 
-        raw_local_irq_save(flags);
+        local_irq_save(flags);
         __raw_spin_lock(&max_stack_lock);
         *ptr = val;
         __raw_spin_unlock(&max_stack_lock);
-        raw_local_irq_restore(flags);
+        local_irq_restore(flags);
 
         return count;
 }
 
-static struct file_operations stack_max_size_fops = {
+static const struct file_operations stack_max_size_fops = {
         .open           = tracing_open_generic,
         .read           = stack_max_size_read,
         .write          = stack_max_size_write,
@@ -184,11 +188,16 @@ static struct file_operations stack_max_size_fops = {
 static void *
 t_next(struct seq_file *m, void *v, loff_t *pos)
 {
-        long i = (long)m->private;
+        long i;
 
         (*pos)++;
 
-        i++;
+        if (v == SEQ_START_TOKEN)
+                i = 0;
+        else {
+                i = *(long *)v;
+                i++;
+        }
 
         if (i >= max_stack_trace.nr_entries ||
             stack_dump_trace[i] == ULONG_MAX)
@@ -201,12 +210,15 @@ t_next(struct seq_file *m, void *v, loff_t *pos)
 
 static void *t_start(struct seq_file *m, loff_t *pos)
 {
-        void *t = &m->private;
+        void *t = SEQ_START_TOKEN;
         loff_t l = 0;
 
         local_irq_disable();
         __raw_spin_lock(&max_stack_lock);
 
+        if (*pos == 0)
+                return SEQ_START_TOKEN;
+
         for (; t && l < *pos; t = t_next(m, t, &l))
                 ;
 
@@ -235,10 +247,10 @@ static int trace_lookup_stack(struct seq_file *m, long i)
 
 static int t_show(struct seq_file *m, void *v)
 {
-        long i = *(long *)v;
+        long i;
         int size;
 
-        if (i < 0) {
+        if (v == SEQ_START_TOKEN) {
                 seq_printf(m, "        Depth   Size      Location"
                            "    (%d entries)\n"
                            "        -----   ----      --------\n",
@@ -246,6 +258,8 @@ static int t_show(struct seq_file *m, void *v)
                 return 0;
         }
 
+        i = *(long *)v;
+
         if (i >= max_stack_trace.nr_entries ||
             stack_dump_trace[i] == ULONG_MAX)
                 return 0;
@@ -263,7 +277,7 @@ static int t_show(struct seq_file *m, void *v)
         return 0;
 }
 
-static struct seq_operations stack_trace_seq_ops = {
+static const struct seq_operations stack_trace_seq_ops = {
         .start          = t_start,
         .next           = t_next,
         .stop           = t_stop,
@@ -275,20 +289,51 @@ static int stack_trace_open(struct inode *inode, struct file *file)
         int ret;
 
         ret = seq_open(file, &stack_trace_seq_ops);
-        if (!ret) {
-                struct seq_file *m = file->private_data;
-                m->private = (void *)-1;
-        }
 
         return ret;
 }
 
-static struct file_operations stack_trace_fops = {
+static const struct file_operations stack_trace_fops = {
         .open           = stack_trace_open,
         .read           = seq_read,
         .llseek         = seq_lseek,
 };
 
+int
+stack_trace_sysctl(struct ctl_table *table, int write,
+                   struct file *file, void __user *buffer, size_t *lenp,
+                   loff_t *ppos)
+{
+        int ret;
+
+        mutex_lock(&stack_sysctl_mutex);
+
+        ret = proc_dointvec(table, write, file, buffer, lenp, ppos);
+
+        if (ret || !write ||
+            (last_stack_tracer_enabled == stack_tracer_enabled))
+                goto out;
+
+        last_stack_tracer_enabled = stack_tracer_enabled;
+
+        if (stack_tracer_enabled)
+                register_ftrace_function(&trace_ops);
+        else
+                unregister_ftrace_function(&trace_ops);
+
+ out:
+        mutex_unlock(&stack_sysctl_mutex);
+        return ret;
+}
+
+static __init int enable_stacktrace(char *str)
+{
+        stack_tracer_enabled = 1;
+        last_stack_tracer_enabled = 1;
+        return 1;
+}
+__setup("stacktrace", enable_stacktrace);
+
 static __init int stack_trace_init(void)
 {
         struct dentry *d_tracer;
@@ -306,7 +351,8 @@ static __init int stack_trace_init(void)
         if (!entry)
                 pr_warning("Could not create debugfs 'stack_trace' entry\n");
 
-        register_ftrace_function(&trace_ops);
+        if (stack_tracer_enabled)
+                register_ftrace_function(&trace_ops);
 
         return 0;
 }