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SubjectRe: [PATCH 2/2] tracing/filter: remove empty subsystem and it's directory
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On Thu, 2009-07-09 at 16:22 +0800, Xiao Guangrong wrote:
> Remove empty subsystem and it's directory when module unload.
>
> Before patch:
> # rmmod trace-events-sample.ko
> # ls sample
> enable filter
>
> After patch:
> # rmmod trace-events-sample.ko
> # ls sample
> ls: cannot access sample: No such file or directory
>
> Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>

Looks like it does the trick.

Acked-by: Tom Zanussi <tzanussi@gmail.com>

> ---
> kernel/trace/trace.h | 1 +
> kernel/trace/trace_events.c | 32 +++++++++++++++++++++++++++++++-
> 2 files changed, 32 insertions(+), 1 deletions(-)
>
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index 61b4e94..0e7de4b 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -780,6 +780,7 @@ struct event_subsystem {
> const char *name;
> struct dentry *entry;
> void *filter;
> + int nr_events;
> };
>
> struct filter_pred;
> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
> index fecac13..90cf936 100644
> --- a/kernel/trace/trace_events.c
> +++ b/kernel/trace/trace_events.c
> @@ -851,8 +851,10 @@ event_subsystem_dir(const char *name, struct dentry *d_events)
>
> /* First see if we did not already create this dir */
> list_for_each_entry(system, &event_subsystems, list) {
> - if (strcmp(system->name, name) == 0)
> + if (strcmp(system->name, name) == 0) {
> + system->nr_events++;
> return system->entry;
> + }
> }
>
> /* need to create new entry */
> @@ -871,6 +873,7 @@ event_subsystem_dir(const char *name, struct dentry *d_events)
> return d_events;
> }
>
> + system->nr_events = 1;
> system->name = kstrdup(name, GFP_KERNEL);
> if (!system->name) {
> debugfs_remove(system->entry);
> @@ -905,6 +908,32 @@ event_subsystem_dir(const char *name, struct dentry *d_events)
> return system->entry;
> }
>
> +static void remove_subsystem_dir(const char *name)
> +{
> + struct event_subsystem *system;
> +
> + if (strcmp(name, TRACE_SYSTEM) == 0)
> + return;
> +
> + list_for_each_entry(system, &event_subsystems, list) {
> + if (strcmp(system->name, name) == 0) {
> + if (!--system->nr_events) {
> + struct event_filter *filter = system->filter;
> +
> + debugfs_remove_recursive(system->entry);
> + list_del(&system->list);
> + if (filter) {
> + kfree(filter->filter_string);
> + kfree(filter);
> + }
> + kfree(system->name);
> + kfree(system);
> + }
> + break;
> + }
> + }
> +}
> +
> static int
> event_create_dir(struct ftrace_event_call *call, struct dentry *d_events,
> const struct file_operations *id,
> @@ -1079,6 +1108,7 @@ static void trace_module_remove_events(struct module *mod)
> list_del(&call->list);
> trace_destroy_fields(call);
> destroy_preds(call);
> + remove_subsystem_dir(call->system);
> }
> }
>



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