[PATCH 06/18] ftrace: Cleanup regex_lock and ftrace_lock around hash updating

Steven Rostedt
2013-05-11T00:13:37Z

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From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>

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>
---
kernel/trace/ftrace.c | 59 +++++++++++++++++++++++++++----------------------
1 file changed, 32 insertions(+), 27 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 827f2fe..cacf085 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;
}