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Date: Wed, 12 Sep 2012 00:38:25 -0300
From: Ezequiel Garcia <elezegarcia@...il.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: linux-kernel@...r.kernel.org, Pekka Enberg <penberg@...nel.org>,
tim.bird@...sony.com, Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH v3] trace: Move trace event enable from fs_initcall to core_initcall
On Tue, Sep 11, 2012 at 9:34 PM, Steven Rostedt <rostedt@...dmis.org> wrote:
> On Sat, 2012-09-08 at 17:01 -0300, Ezequiel Garcia wrote:
>> This patch splits trace event initialization in two stages:
>> * ftrace enable
>> * sysfs event entry creation
>>
>> This allows to capture trace events from an earlier point
>> by using 'trace_event' kernel parameter and is important
>> to trace boot-up allocations.
>>
>> Note that, in order to enable events at core_initcall,
>> it's necessary to move init_ftrace_syscalls() from
>> core_initcall to early_initcall.
>
> Found another issue...
>
>>
>> Cc: Steven Rostedt <rostedt@...dmis.org>
>> Signed-off-by: Ezequiel Garcia <elezegarcia@...il.com>
>> ---
>> Changes from v1:
>> * Rework code as requested by Steven.
>>
>> Changes from v2:
>> * Move init_ftrace_syscalls() to early_initcall,
>> so syscalls self-test pass.
>>
>> kernel/trace/trace_events.c | 104 +++++++++++++++++++++++++++-------------
>> kernel/trace/trace_syscalls.c | 2 +-
>> 2 files changed, 71 insertions(+), 35 deletions(-)
>>
>> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
>> index 29111da..4eaf86e 100644
>> --- a/kernel/trace/trace_events.c
>> +++ b/kernel/trace/trace_events.c
>> @@ -1199,6 +1199,31 @@ event_create_dir(struct ftrace_event_call *call, struct dentry *d_events,
>> return 0;
>> }
>>
>> +static void event_remove(struct ftrace_event_call *call)
>> +{
>> + ftrace_event_enable_disable(call, 0);
>> + if (call->event.funcs)
>> + __unregister_ftrace_event(&call->event);
>> + list_del(&call->list);
>> +}
>> +
>> +static int event_init(struct ftrace_event_call *call)
>> +{
>> + int ret = 0;
>> +
>> + if (WARN_ON(!call->name))
>> + return -EINVAL;
>> +
>> + if (call->class->raw_init) {
>> + ret = call->class->raw_init(call);
>
> If raw_init() returns a failure, we skip this event.
>
>> + if (ret < 0 && ret != -ENOSYS)
>> + pr_warn("Could not initialize trace events/%s\n",
>> + call->name);
>> + }
>> +
>> + return ret;
>> +}
>> +
>> static int
>> __trace_add_event_call(struct ftrace_event_call *call, struct module *mod,
>> const struct file_operations *id,
>> @@ -1209,19 +1234,9 @@ __trace_add_event_call(struct ftrace_event_call *call, struct module *mod,
>> struct dentry *d_events;
>> int ret;
>>
>> - /* The linker may leave blanks */
>> - if (!call->name)
>> - return -EINVAL;
>> -
>> - if (call->class->raw_init) {
>> - ret = call->class->raw_init(call);
>> - if (ret < 0) {
>> - if (ret != -ENOSYS)
>> - pr_warning("Could not initialize trace events/%s\n",
>> - call->name);
>> - return ret;
>> - }
>> - }
>> + ret = event_init(call);
>> + if (ret < 0)
>> + return ret;
>>
>> d_events = event_trace_events_dir();
>> if (!d_events)
>> @@ -1272,13 +1287,10 @@ static void remove_subsystem_dir(const char *name)
>> */
>> static void __trace_remove_event_call(struct ftrace_event_call *call)
>> {
>> - ftrace_event_enable_disable(call, 0);
>> - if (call->event.funcs)
>> - __unregister_ftrace_event(&call->event);
>> - debugfs_remove_recursive(call->dir);
>> - list_del(&call->list);
>> + event_remove(call);
>> trace_destroy_fields(call);
>> destroy_preds(call);
>> + debugfs_remove_recursive(call->dir);
>> remove_subsystem_dir(call->class->system);
>> }
>>
>> @@ -1450,6 +1462,36 @@ static __init int setup_trace_event(char *str)
>> }
>> __setup("trace_event=", setup_trace_event);
>>
>> +static __init int event_trace_enable(void)
>> +{
>> + struct ftrace_event_call **iter, *call;
>> + char *buf = bootup_event_buf;
>> + char *token;
>> + int ret;
>> +
>> + for_each_event(iter, __start_ftrace_events, __stop_ftrace_events) {
>> +
>> + call = *iter;
>> + ret = event_init(call);
>> + if (!ret)
>> + list_add(&call->list, &ftrace_events);
>> + }
>> +
>> + while (true) {
>> + token = strsep(&buf, ",");
>> +
>> + if (!token)
>> + break;
>> + if (!*token)
>> + continue;
>> +
>> + ret = ftrace_set_clr_event(token, 1);
>> + if (ret)
>> + pr_warn("Failed to enable trace event: %s\n", token);
>> + }
>> + return 0;
>> +}
>> +
>> static __init int event_trace_init(void)
>> {
>> struct ftrace_event_call **call;
>> @@ -1457,8 +1499,6 @@ static __init int event_trace_init(void)
>> struct dentry *entry;
>> struct dentry *d_events;
>> int ret;
>> - char *buf = bootup_event_buf;
>> - char *token;
>>
>> d_tracer = tracing_init_dentry();
>> if (!d_tracer)
>> @@ -1497,24 +1537,19 @@ static __init int event_trace_init(void)
>> if (trace_define_common_fields())
>> pr_warning("tracing: Failed to allocate common fields");
>>
>> + /*
>> + * Early initialization already enabled ftrace event.
>> + * Now it's only necessary to create the event directory.
>> + */
>> for_each_event(call, __start_ftrace_events, __stop_ftrace_events) {
>> - __trace_add_event_call(*call, NULL, &ftrace_event_id_fops,
>
> Here, __trace_add_event_call() did the checks and did not create a
> directory on raw_init() failure. But now there's no check, and we are
> having events being created that should not be.
>
Mmmm... I see.
>> +
>> + ret = event_create_dir(*call, d_events,
>> + &ftrace_event_id_fops,
>> &ftrace_enable_fops,
>> &ftrace_event_filter_fops,
>> &ftrace_event_format_fops);
>
> I found this out when there was errors in trace-cmd reading format
> files. Looking into it, I found several syscalls that are not mapped to
> a syscall_nr being created.
>
> One solution would be to add another flag to the ftrace_event_call
> structure, that notes the event has failed to initialize. Or better yet,
> add a flag that just says that it was initialized. Then here we can skip
> those events that do not have that flag set.
>
Ok. I'll re-send.
Thanks!
Ezequiel.
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