[PATCH 1/2] tracing: Miscellaneous fixes for trace_array ref counting

[PATCH 1/2] tracing: Miscellaneous fixes for trace_array ref counting

[Alexander Z Lam]

Some error paths did not handle ref counting properly, and some trace files need
ref counting.

Cc: Vaibhav Nagarnaik <vnagarnaik@google.com>
Cc: David Sharp <dhsharp@google.com>
Cc: Alexander Z Lam <lambchop468@gmail.com>
Signed-off-by: Alexander Z Lam <azl@google.com>
---
 kernel/trace/trace.c        | 34 +++++++++++++++++++++++-----------
 kernel/trace/trace_events.c | 21 +++++++++++++++++++--
 2 files changed, 42 insertions(+), 13 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 0cd500b..ca2743b 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3008,7 +3008,6 @@ static int tracing_release(struct inode *inode, struct file *file)
 
 	iter = m->private;
 	tr = iter->tr;
-	trace_array_put(tr);
 
 	mutex_lock(&trace_types_lock);
 
@@ -3023,6 +3022,9 @@ static int tracing_release(struct inode *inode, struct file *file)
 	if (!iter->snapshot)
 		/* reenable tracing if it was previously enabled */
 		tracing_start_tr(tr);
+
+	__trace_array_put(tr);
+
 	mutex_unlock(&trace_types_lock);
 
 	mutex_destroy(&iter->mutex);
@@ -3447,6 +3449,7 @@ tracing_trace_options_write(struct file *filp, const char __user *ubuf,
 static int tracing_trace_options_open(struct inode *inode, struct file *file)
 {
 	struct trace_array *tr = inode->i_private;
+	int ret;
 
 	if (tracing_disabled)
 		return -ENODEV;
@@ -3454,7 +3457,11 @@ static int tracing_trace_options_open(struct inode *inode, struct file *file)
 	if (trace_array_get(tr) < 0)
 		return -ENODEV;
 
-	return single_open(file, tracing_trace_options_show, inode->i_private);
+	ret = single_open(file, tracing_trace_options_show, inode->i_private);
+	if (ret < 0)
+		trace_array_put(tr);
+
+	return ret;
 }
 
 static const struct file_operations tracing_iter_fops = {
@@ -3958,7 +3965,7 @@ static int tracing_open_pipe(struct inode *inode, struct file *filp)
 	iter = kzalloc(sizeof(*iter), GFP_KERNEL);
 	if (!iter) {
 		ret = -ENOMEM;
-		goto out;
+		goto fail_iter;
 	}
 
 	/*
@@ -3968,13 +3975,13 @@ static int tracing_open_pipe(struct inode *inode, struct file *filp)
 	iter->trace = kmalloc(sizeof(*iter->trace), GFP_KERNEL);
 	if (!iter->trace) {
 		ret = -ENOMEM;
-		goto fail;
+		goto fail_trace;
 	}
 	*iter->trace = *tr->current_trace;
 
 	if (!alloc_cpumask_var(&iter->started, GFP_KERNEL)) {
 		ret = -ENOMEM;
-		goto fail;
+		goto fail_trace;
 	}
 
 	/* trace pipe does not show start of buffer */
@@ -4001,9 +4008,10 @@ out:
 	mutex_unlock(&trace_types_lock);
 	return ret;
 
-fail:
+fail_trace:
 	kfree(iter->trace);
 	kfree(iter);
+fail_iter:
 	__trace_array_put(tr);
 	mutex_unlock(&trace_types_lock);
 	return ret;
@@ -4705,12 +4713,15 @@ static int tracing_snapshot_open(struct inode *inode, struct file *file)
 	} else {
 		/* Writes still need the seq_file to hold the private data */
 		m = kzalloc(sizeof(*m), GFP_KERNEL);
-		if (!m)
-			return -ENOMEM;
+		if (!m) {
+			ret = -ENOMEM;
+			goto out;
+		}
 		iter = kzalloc(sizeof(*iter), GFP_KERNEL);
 		if (!iter) {
 			kfree(m);
-			return -ENOMEM;
+			ret = -ENOMEM;
+			goto out;
 		}
 		iter->tr = tr;
 		iter->trace_buffer = &tc->tr->max_buffer;
@@ -4718,7 +4729,7 @@ static int tracing_snapshot_open(struct inode *inode, struct file *file)
 		m->private = iter;
 		file->private_data = m;
 	}
-
+out:
 	if (ret < 0)
 		trace_array_put(tr);
 
@@ -5328,9 +5339,10 @@ tracing_stats_read(struct file *filp, char __user *ubuf,
 }
 
 static const struct file_operations tracing_stats_fops = {
-	.open		= tracing_open_generic,
+	.open		= tracing_open_generic_tc,
 	.read		= tracing_stats_read,
 	.llseek		= generic_file_llseek,
+	.release	= tracing_release_generic_tc,
 };
 
 #ifdef CONFIG_DYNAMIC_FTRACE
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 7d85429..7a75cb2 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1218,6 +1218,7 @@ show_header(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos)
 
 static int ftrace_event_avail_open(struct inode *inode, struct file *file);
 static int ftrace_event_set_open(struct inode *inode, struct file *file);
+static int ftrace_event_release(struct inode *inode, struct file *file);
 
 static const struct seq_operations show_event_seq_ops = {
 	.start = t_start,
@@ -1245,7 +1246,7 @@ static const struct file_operations ftrace_set_event_fops = {
 	.read = seq_read,
 	.write = ftrace_event_write,
 	.llseek = seq_lseek,
-	.release = seq_release,
+	.release = ftrace_event_release,
 };
 
 static const struct file_operations ftrace_enable_fops = {
@@ -1323,6 +1324,15 @@ ftrace_event_open(struct inode *inode, struct file *file,
 	return ret;
 }
 
+static int ftrace_event_release(struct inode *inode, struct file *file)
+{
+	struct trace_array *tr = inode->i_private;
+
+	trace_array_put(tr);
+
+	return seq_release(inode, file);
+}
+
 static int
 ftrace_event_avail_open(struct inode *inode, struct file *file)
 {
@@ -1336,12 +1346,19 @@ ftrace_event_set_open(struct inode *inode, struct file *file)
 {
 	const struct seq_operations *seq_ops = &show_set_event_seq_ops;
 	struct trace_array *tr = inode->i_private;
+	int ret;
+
+	if (trace_array_get(tr) < 0)
+		return -ENODEV;
 
 	if ((file->f_mode & FMODE_WRITE) &&
 	    (file->f_flags & O_TRUNC))
 		ftrace_clear_events(tr);
 
-	return ftrace_event_open(inode, file, seq_ops);
+	ret = ftrace_event_open(inode, file, seq_ops);
+	if (ret < 0)
+		trace_array_put(tr);
+	return ret;
 }
 
 static struct event_subsystem *
-- 
1.8.3

[PATCH 2/2] tracing: Fix error handling to ensure instances can always be removed

[Alexander Z Lam]

Remove debugfs directories for tracing instances during creation if an error
occurs causing the trace_array for that instance to not be added to
ftrace_trace_arrays. If the directory continues to exist after the error, it
cannot be removed because the respective trace_array is not in
ftrace_trace_arrays.

Cc: Vaibhav Nagarnaik <vnagarnaik@google.com>
Cc: David Sharp <dhsharp@google.com>
Cc: Alexander Z Lam <lambchop468@gmail.com>
Signed-off-by: Alexander Z Lam <azl@google.com>
---
 kernel/trace/trace.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index ca2743b..4ea9967 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -5985,8 +5985,10 @@ static int new_instance_create(const char *name)
 		goto out_free_tr;
 
 	ret = event_trace_add_tracer(tr->dir, tr);
-	if (ret)
+	if (ret) {
+		debugfs_remove_recursive(tr->dir);
 		goto out_free_tr;
+	}
 
 	init_tracer_debugfs(tr, tr->dir);
 
-- 
1.8.3

Re: [PATCH 1/2] tracing: Miscellaneous fixes for trace_array ref counting

[Steven Rostedt]

On Wed, 2013-07-10 at 17:34 -0700, Alexander Z Lam wrote:
> Some error paths did not handle ref counting properly, and some trace files need
> ref counting.
> 
> Cc: Vaibhav Nagarnaik <vnagarnaik@google.com>
> Cc: David Sharp <dhsharp@google.com>
> Cc: Alexander Z Lam <lambchop468@gmail.com>
> Signed-off-by: Alexander Z Lam <azl@google.com>
> ---
>  kernel/trace/trace.c        | 34 +++++++++++++++++++++++-----------
>  kernel/trace/trace_events.c | 21 +++++++++++++++++++--
>  2 files changed, 42 insertions(+), 13 deletions(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 0cd500b..ca2743b 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -3008,7 +3008,6 @@ static int tracing_release(struct inode *inode, struct file *file)
>  
>  	iter = m->private;
>  	tr = iter->tr;
> -	trace_array_put(tr);
>  
>  	mutex_lock(&trace_types_lock);
>  
> @@ -3023,6 +3022,9 @@ static int tracing_release(struct inode *inode, struct file *file)
>  	if (!iter->snapshot)
>  		/* reenable tracing if it was previously enabled */
>  		tracing_start_tr(tr);
> +
> +	__trace_array_put(tr);
> +
>  	mutex_unlock(&trace_types_lock);
>  
>  	mutex_destroy(&iter->mutex);
> @@ -3447,6 +3449,7 @@ tracing_trace_options_write(struct file *filp, const char __user *ubuf,
>  static int tracing_trace_options_open(struct inode *inode, struct file *file)
>  {
>  	struct trace_array *tr = inode->i_private;
> +	int ret;
>  
>  	if (tracing_disabled)
>  		return -ENODEV;
> @@ -3454,7 +3457,11 @@ static int tracing_trace_options_open(struct inode *inode, struct file *file)
>  	if (trace_array_get(tr) < 0)
>  		return -ENODEV;
>  
> -	return single_open(file, tracing_trace_options_show, inode->i_private);
> +	ret = single_open(file, tracing_trace_options_show, inode->i_private);
> +	if (ret < 0)
> +		trace_array_put(tr);
> +
> +	return ret;
>  }
>  
>  static const struct file_operations tracing_iter_fops = {
> @@ -3958,7 +3965,7 @@ static int tracing_open_pipe(struct inode *inode, struct file *filp)
>  	iter = kzalloc(sizeof(*iter), GFP_KERNEL);
>  	if (!iter) {
>  		ret = -ENOMEM;
> -		goto out;
> +		goto fail_iter;

It would be cleaner to not add the extra label, and just do a
trace_array_put() in the if statement.


>  	}
>  
>  	/*
> @@ -3968,13 +3975,13 @@ static int tracing_open_pipe(struct inode *inode, struct file *filp)
>  	iter->trace = kmalloc(sizeof(*iter->trace), GFP_KERNEL);
>  	if (!iter->trace) {
>  		ret = -ENOMEM;
> -		goto fail;
> +		goto fail_trace;
>  	}
>  	*iter->trace = *tr->current_trace;
>  
>  	if (!alloc_cpumask_var(&iter->started, GFP_KERNEL)) {
>  		ret = -ENOMEM;
> -		goto fail;
> +		goto fail_trace;
>  	}
>  
>  	/* trace pipe does not show start of buffer */
> @@ -4001,9 +4008,10 @@ out:
>  	mutex_unlock(&trace_types_lock);
>  	return ret;
>  
> -fail:
> +fail_trace:
>  	kfree(iter->trace);
>  	kfree(iter);
> +fail_iter:
>  	__trace_array_put(tr);
>  	mutex_unlock(&trace_types_lock);
>  	return ret;
> @@ -4705,12 +4713,15 @@ static int tracing_snapshot_open(struct inode *inode, struct file *file)
>  	} else {
>  		/* Writes still need the seq_file to hold the private data */
>  		m = kzalloc(sizeof(*m), GFP_KERNEL);
> -		if (!m)
> -			return -ENOMEM;
> +		if (!m) {
> +			ret = -ENOMEM;
> +			goto out;
> +		}

Instead of adding the complex if statement, do this:


	int ret = -ENOMEM;

	[..]

	if (!m)
		goto out;

And then after the if statements:

	ret = 0;

>  		iter = kzalloc(sizeof(*iter), GFP_KERNEL);
>  		if (!iter) {
>  			kfree(m);
> -			return -ENOMEM;
> +			ret = -ENOMEM;
> +			goto out;
>  		}
>  		iter->tr = tr;
>  		iter->trace_buffer = &tc->tr->max_buffer;
> @@ -4718,7 +4729,7 @@ static int tracing_snapshot_open(struct inode *inode, struct file *file)
>  		m->private = iter;
>  		file->private_data = m;
>  	}
> -
> +out:
>  	if (ret < 0)
>  		trace_array_put(tr);
>  

The rest looks good. Although, we may be rewriting all this code because
there still exists some races. See the email threads between Oleg and
Masami.

-- Steve


> @@ -5328,9 +5339,10 @@ tracing_stats_read(struct file *filp, char __user *ubuf,
>  }
>  
>  static const struct file_operations tracing_stats_fops = {
> -	.open		= tracing_open_generic,
> +	.open		= tracing_open_generic_tc,
>  	.read		= tracing_stats_read,
>  	.llseek		= generic_file_llseek,
> +	.release	= tracing_release_generic_tc,
>  };
>  
>  #ifdef CONFIG_DYNAMIC_FTRACE
> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
> index 7d85429..7a75cb2 100644
> --- a/kernel/trace/trace_events.c
> +++ b/kernel/trace/trace_events.c
> @@ -1218,6 +1218,7 @@ show_header(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos)
>  
>  static int ftrace_event_avail_open(struct inode *inode, struct file *file);
>  static int ftrace_event_set_open(struct inode *inode, struct file *file);
> +static int ftrace_event_release(struct inode *inode, struct file *file);
>  
>  static const struct seq_operations show_event_seq_ops = {
>  	.start = t_start,
> @@ -1245,7 +1246,7 @@ static const struct file_operations ftrace_set_event_fops = {
>  	.read = seq_read,
>  	.write = ftrace_event_write,
>  	.llseek = seq_lseek,
> -	.release = seq_release,
> +	.release = ftrace_event_release,
>  };
>  
>  static const struct file_operations ftrace_enable_fops = {
> @@ -1323,6 +1324,15 @@ ftrace_event_open(struct inode *inode, struct file *file,
>  	return ret;
>  }
>  
> +static int ftrace_event_release(struct inode *inode, struct file *file)
> +{
> +	struct trace_array *tr = inode->i_private;
> +
> +	trace_array_put(tr);
> +
> +	return seq_release(inode, file);
> +}
> +
>  static int
>  ftrace_event_avail_open(struct inode *inode, struct file *file)
>  {
> @@ -1336,12 +1346,19 @@ ftrace_event_set_open(struct inode *inode, struct file *file)
>  {
>  	const struct seq_operations *seq_ops = &show_set_event_seq_ops;
>  	struct trace_array *tr = inode->i_private;
> +	int ret;
> +
> +	if (trace_array_get(tr) < 0)
> +		return -ENODEV;
>  
>  	if ((file->f_mode & FMODE_WRITE) &&
>  	    (file->f_flags & O_TRUNC))
>  		ftrace_clear_events(tr);
>  
> -	return ftrace_event_open(inode, file, seq_ops);
> +	ret = ftrace_event_open(inode, file, seq_ops);
> +	if (ret < 0)
> +		trace_array_put(tr);
> +	return ret;
>  }
>  
>  static struct event_subsystem *

Re: [PATCH 2/2] tracing: Fix error handling to ensure instances can always be removed

[Steven Rostedt]

On Wed, 2013-07-10 at 17:34 -0700, Alexander Z Lam wrote:
> Remove debugfs directories for tracing instances during creation if an error
> occurs causing the trace_array for that instance to not be added to
> ftrace_trace_arrays. If the directory continues to exist after the error, it
> cannot be removed because the respective trace_array is not in
> ftrace_trace_arrays.

This patch is fine, I'll put it in now.

Thanks,

-- Steve

> 
> Cc: Vaibhav Nagarnaik <vnagarnaik@google.com>
> Cc: David Sharp <dhsharp@google.com>
> Cc: Alexander Z Lam <lambchop468@gmail.com>
> Signed-off-by: Alexander Z Lam <azl@google.com>
> ---
>  kernel/trace/trace.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index ca2743b..4ea9967 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -5985,8 +5985,10 @@ static int new_instance_create(const char *name)
>  		goto out_free_tr;
>  
>  	ret = event_trace_add_tracer(tr->dir, tr);
> -	if (ret)
> +	if (ret) {
> +		debugfs_remove_recursive(tr->dir);
>  		goto out_free_tr;
> +	}
>  
>  	init_tracer_debugfs(tr, tr->dir);
>