ftrace: Cleanup regex_lock and ftrace_lock around hash updating

Cleanup regex_lock and ftrace_lock locking points around
ftrace_ops hash update code.

The new rule is that regex_lock protects ops->*_hash
read-update-write code for each ftrace_ops. Usually,
hash update is done by following sequence.

1. allocate a new local hash and copy the original hash.
2. update the local hash.
3. move(actually, copy) back the local hash to ftrace_ops.
4. update ftrace entries if needed.
5. release the local hash.

This makes regex_lock protect #1-#4, and ftrace_lock
to protect #3, #4 and adding and removing ftrace_ops from the
ftrace_ops_list. The ftrace_lock protects #3 as well because
the move functions update the entries too.

Link: http://lkml.kernel.org/r/20130509054421.30398.83411.stgit@mhiramat-M0-7522

Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Tom Zanussi <tom.zanussi@intel.com>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 32 insertions, 27 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 827f2fe7bc3f..cacf0856191e 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2656,28 +2656,26 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag,
                 return -ENOMEM;
         }
 
+        iter->ops = ops;
+        iter->flags = flag;
+
+        mutex_lock(&ops->regex_lock);
+
         if (flag & FTRACE_ITER_NOTRACE)
                 hash = ops->notrace_hash;
         else
                 hash = ops->filter_hash;
 
-        iter->ops = ops;
-        iter->flags = flag;
-
         if (file->f_mode & FMODE_WRITE) {
-                mutex_lock(&ftrace_lock);
                 iter->hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, hash);
-                mutex_unlock(&ftrace_lock);
-
                 if (!iter->hash) {
                         trace_parser_put(&iter->parser);
                         kfree(iter);
-                        return -ENOMEM;
+                        ret = -ENOMEM;
+                        goto out_unlock;
                 }
         }
 
-        mutex_lock(&ops->regex_lock);
-
         if ((file->f_mode & FMODE_WRITE) &&
             (file->f_flags & O_TRUNC))
                 ftrace_filter_reset(iter->hash);
@@ -2697,6 +2695,8 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag,
                 }
         } else
                 file->private_data = iter;
+
+ out_unlock:
         mutex_unlock(&ops->regex_lock);
 
         return ret;
@@ -3012,7 +3012,7 @@ register_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
         if (WARN_ON(not))
                 return -EINVAL;
 
-        mutex_lock(&ftrace_lock);
+        mutex_lock(&trace_probe_ops.regex_lock);
 
         hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, *orig_hash);
         if (!hash) {
@@ -3070,14 +3070,16 @@ register_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
 
         } while_for_each_ftrace_rec();
 
+        mutex_lock(&ftrace_lock);
         ret = ftrace_hash_move(&trace_probe_ops, 1, orig_hash, hash);
         if (ret < 0)
                 count = ret;
 
         __enable_ftrace_function_probe();
+        mutex_unlock(&ftrace_lock);
 
  out_unlock:
-        mutex_unlock(&ftrace_lock);
+        mutex_unlock(&trace_probe_ops.regex_lock);
         free_ftrace_hash(hash);
 
         return count;
@@ -3117,7 +3119,7 @@ __unregister_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
                         return;
         }
 
-        mutex_lock(&ftrace_lock);
+        mutex_lock(&trace_probe_ops.regex_lock);
 
         hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, *orig_hash);
         if (!hash)
@@ -3155,6 +3157,7 @@ __unregister_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
                         list_add(&entry->free_list, &free_list);
                 }
         }
+        mutex_lock(&ftrace_lock);
         __disable_ftrace_function_probe();
         /*
          * Remove after the disable is called. Otherwise, if the last
@@ -3166,9 +3169,10 @@ __unregister_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
                 list_del(&entry->free_list);
                 ftrace_free_entry(entry);
         }
+        mutex_unlock(&ftrace_lock);
                 
  out_unlock:
-        mutex_unlock(&ftrace_lock);
+        mutex_unlock(&trace_probe_ops.regex_lock);
         free_ftrace_hash(hash);
 }
 
@@ -3284,11 +3288,10 @@ ftrace_regex_write(struct file *file, const char __user *ubuf,
         } else
                 iter = file->private_data;
 
-        mutex_lock(&iter->ops->regex_lock);
-
-        ret = -ENODEV;
         if (unlikely(ftrace_disabled))
-                goto out_unlock;
+                return -ENODEV;
+
+        /* iter->hash is a local copy, so we don't need regex_lock */
 
         parser = &iter->parser;
         read = trace_get_user(parser, ubuf, cnt, ppos);
@@ -3299,13 +3302,11 @@ ftrace_regex_write(struct file *file, const char __user *ubuf,
                                            parser->idx, enable);
                 trace_parser_clear(parser);
                 if (ret < 0)
-                        goto out_unlock;
+                        goto out;
         }
 
         ret = read;
-out_unlock:
-        mutex_unlock(&iter->ops->regex_lock);
-
+ out:
         return ret;
 }
 
@@ -3357,16 +3358,19 @@ ftrace_set_hash(struct ftrace_ops *ops, unsigned char *buf, int len,
         if (unlikely(ftrace_disabled))
                 return -ENODEV;
 
+        mutex_lock(&ops->regex_lock);
+
         if (enable)
                 orig_hash = &ops->filter_hash;
         else
                 orig_hash = &ops->notrace_hash;
 
         hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, *orig_hash);
-        if (!hash)
-                return -ENOMEM;
+        if (!hash) {
+                ret = -ENOMEM;
+                goto out_regex_unlock;
+        }
 
-        mutex_lock(&ops->regex_lock);
         if (reset)
                 ftrace_filter_reset(hash);
         if (buf && !ftrace_match_records(hash, buf, len)) {
@@ -3584,8 +3588,6 @@ int ftrace_regex_release(struct inode *inode, struct file *file)
         } else
                 iter = file->private_data;
 
-        mutex_lock(&iter->ops->regex_lock);
-
         parser = &iter->parser;
         if (trace_parser_loaded(parser)) {
                 parser->buffer[parser->idx] = 0;
@@ -3594,6 +3596,8 @@ int ftrace_regex_release(struct inode *inode, struct file *file)
 
         trace_parser_put(parser);
 
+        mutex_lock(&iter->ops->regex_lock);
+
         if (file->f_mode & FMODE_WRITE) {
                 filter_hash = !!(iter->flags & FTRACE_ITER_FILTER);
 
@@ -3611,10 +3615,11 @@ int ftrace_regex_release(struct inode *inode, struct file *file)
 
                 mutex_unlock(&ftrace_lock);
         }
+
+        mutex_unlock(&iter->ops->regex_lock);
         free_ftrace_hash(iter->hash);
         kfree(iter);
 
-        mutex_unlock(&iter->ops->regex_lock);
         return 0;
 }