Commit 1a11126b authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Steven Rostedt
Browse files

tracing: Turn event/id->i_private into call->event.type 

event_id_read() is racy, ftrace_event_call can be already freed
by trace_remove_event_call() callers.

Change event_create_dir() to pass "data = call->event.type", this
is all event_id_read() needs. ftrace_event_id_fops no longer needs
tracing_open_generic().

We add the new helper, event_file_data(), to read ->i_private, it
will have more users.

Note: currently ACCESS_ONCE() and "id != 0" check are not needed,
but we are going to change event_remove/rmdir to clear ->i_private.

Link: http://lkml.kernel.org/r/20130726172532.GA3605@redhat.com



Reviewed-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 5ae90d8e

kernel/trace/trace_events.c

+13 −5
Original line number Diff line number Diff line
@@ -409,6 +409,11 @@ static void put_system(struct ftrace_subsystem_dir *dir) 
	mutex_unlock(&event_mutex);

}



static void *event_file_data(struct file *filp)

{

	return ACCESS_ONCE(file_inode(filp)->i_private);

}



/*

 * Open and update trace_array ref count.

 * Must have the current trace_array passed to it.
@@ -946,14 +951,18 @@ static int trace_format_open(struct inode *inode, struct file *file) 
static ssize_t

event_id_read(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos)

{

	struct ftrace_event_call *call = filp->private_data;

	int id = (long)event_file_data(filp);

	char buf[32];

	int len;



	if (*ppos)

		return 0;



	len = sprintf(buf, "%d\n", call->event.type);

	if (unlikely(!id))

		return -ENODEV;



	len = sprintf(buf, "%d\n", id);



	return simple_read_from_buffer(ubuf, cnt, ppos, buf, len);

}
@@ -1240,7 +1249,6 @@ static const struct file_operations ftrace_event_format_fops = { 
};



static const struct file_operations ftrace_event_id_fops = {

	.open = tracing_open_generic,

	.read = event_id_read,

	.llseek = default_llseek,

};
@@ -1488,8 +1496,8 @@ event_create_dir(struct dentry *parent, 


#ifdef CONFIG_PERF_EVENTS

	if (call->event.type && call->class->reg)

		trace_create_file("id", 0444, file->dir, call,

		 		  id);

		trace_create_file("id", 0444, file->dir,

				  (void *)(long)call->event.type, id);

#endif



	/*

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