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

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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: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Oleg Nesterov 2013-07-26 19:25:32 +02:00 committed by Steven Rostedt
parent 5ae90d8e46
commit 1a11126bcb
1 changed files with 13 additions and 5 deletions
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18
kernel/trace/trace_events.c
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@ -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
/*