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SubjectRe: [PATCH 2/2] tracing: Fix rcu handling of event_trigger_data filter field
On Sat, Dec 21, 2013 at 10:08:01PM -0500, Steven Rostedt wrote:
> From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>
>
> The filter field of the event_trigger_data structure is protected under
> RCU sched locks. It was not annotated as such, and after doing so,
> sparse pointed out several locations that required fix ups.
>
> Reported-by: kbuild test robot <fengguang.wu@intel.com>
> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

Looks good to me!

Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

> ---
> kernel/trace/trace.h | 2 +-
> kernel/trace/trace_events_trigger.c | 8 +++++---
> 2 files changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index 0380cab..02b592f 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -1057,7 +1057,7 @@ struct event_trigger_data {
> int ref;
> struct event_trigger_ops *ops;
> struct event_command *cmd_ops;
> - struct event_filter *filter;
> + struct event_filter __rcu *filter;
> char *filter_str;
> void *private_data;
> struct list_head list;
> diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
> index 12ac8a5..f6dd115 100644
> --- a/kernel/trace/trace_events_trigger.c
> +++ b/kernel/trace/trace_events_trigger.c
> @@ -67,6 +67,7 @@ event_triggers_call(struct ftrace_event_file *file, void *rec)
> {
> struct event_trigger_data *data;
> enum event_trigger_type tt = ETT_NONE;
> + struct event_filter *filter;
>
> if (list_empty(&file->triggers))
> return tt;
> @@ -76,7 +77,8 @@ event_triggers_call(struct ftrace_event_file *file, void *rec)
> data->ops->func(data);
> continue;
> }
> - if (data->filter && !filter_match_preds(data->filter, rec))
> + filter = rcu_dereference(data->filter);
> + if (filter && !filter_match_preds(filter, rec))
> continue;
> if (data->cmd_ops->post_trigger) {
> tt |= data->cmd_ops->trigger_type;
> @@ -703,7 +705,7 @@ static int set_trigger_filter(char *filter_str,
> if (ret)
> goto out;
> assign:
> - tmp = data->filter;
> + tmp = rcu_access_pointer(data->filter);
>
> rcu_assign_pointer(data->filter, filter);
>
> @@ -719,7 +721,7 @@ static int set_trigger_filter(char *filter_str,
> if (filter_str) {
> data->filter_str = kstrdup(filter_str, GFP_KERNEL);
> if (!data->filter_str) {
> - free_event_filter(data->filter);
> + free_event_filter(rcu_access_pointer(data->filter));
> data->filter = NULL;
> ret = -ENOMEM;
> }
> --
> 1.8.4.3
>
>



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