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>

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 827f2fe7bc3fa55420d40570c27c1312d2d9f691..cacf0856191e1dd245096720cd9b37870f230fb2 100644 (file)
--- 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;
 }