tracing: add annotation to what type of stack trace is recorded

[safe/jmp/linux-2.6] / kernel / trace / trace_stack.c

diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index 06a1611..2d7aebd 100644 (file)
--- 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)
 {
@@ -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;
@@ -86,12 +92,14 @@ 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:
@@ -171,7 +179,7 @@ stack_max_size_write(struct file *filp, const char __user *ubuf,
        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,
@@ -237,16 +245,31 @@ static int trace_lookup_stack(struct seq_file *m, long i)
 #endif
 }
 
+static void print_disabled(struct seq_file *m)
+{
+       seq_puts(m, "#\n"
+                "#  Stack tracer disabled\n"
+                "#\n"
+                "# To enable the stack tracer, either add 'stacktrace' to the\n"
+                "# kernel command line\n"
+                "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n"
+                "#\n");
+}
+
 static int t_show(struct seq_file *m, void *v)
 {
        long i;
        int size;
 
        if (v == SEQ_START_TOKEN) {
-               seq_printf(m, "        Depth   Size      Location"
+               seq_printf(m, "        Depth    Size   Location"
                           "    (%d entries)\n"
-                          "        -----   ----      --------\n",
-                          max_stack_trace.nr_entries);
+                          "        -----    ----   --------\n",
+                          max_stack_trace.nr_entries - 1);
+
+               if (!stack_tracer_enabled && !max_stack_size)
+                       print_disabled(m);
+
                return 0;
        }
 
@@ -269,7 +292,7 @@ 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,
@@ -285,30 +308,61 @@ static int stack_trace_open(struct inode *inode, struct file *file)
        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;
-       struct dentry *entry;
 
        d_tracer = tracing_init_dentry();
 
-       entry = debugfs_create_file("stack_max_size", 0644, d_tracer,
-                                   &max_stack_size, &stack_max_size_fops);
-       if (!entry)
-               pr_warning("Could not create debugfs 'stack_max_size' entry\n");
+       trace_create_file("stack_max_size", 0644, d_tracer,
+                       &max_stack_size, &stack_max_size_fops);
 
-       entry = debugfs_create_file("stack_trace", 0444, d_tracer,
-                                   NULL, &stack_trace_fops);
-       if (!entry)
-               pr_warning("Could not create debugfs 'stack_trace' entry\n");
+       trace_create_file("stack_trace", 0444, d_tracer,
+                       NULL, &stack_trace_fops);
 
-       register_ftrace_function(&trace_ops);
+       if (stack_tracer_enabled)
+               register_ftrace_function(&trace_ops);
 
        return 0;
 }