Messages in this thread Patch in this message | | | Date | Tue, 21 Apr 2015 12:36:57 +0200 | From | Daniel Wagner <> | Subject | Re: [PATCH v4 0/7] tracing: 'hist' triggers |
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Hi Tom,
On 04/21/2015 12:03 AM, Tom Zanussi wrote: > On Mon, 2015-04-20 at 14:52 +0200, Daniel Wagner wrote: >> On 04/10/2015 06:05 PM, Tom Zanussi wrote: >> So I am wondering if the path from ftrace_trigger_soft_disabled() >> to event_triggers_call() is supposed never to happen? The comment >> on ftrace_trigger_soft_disabled() indicate this might happen on >> normal operation: >> > > So I looked at this on the plane and you're right, this is a path that > should never be taken in this case, since the hist trigger does set the > post_trigger flag and should therefore TRIGGER_COND would be true and > that block should never be entered. > > However, the code that registers the trigger first enables the event, > then sets the cond flag, which would allow this to happen - a trigger > expecting data would be passed a NULL rec. > > Can you try the patch below and see if it fixes the problem? (untested > and I haven't even had a chance to compile-test it..)
Thanks for the explanation. With that and your patch I could get it working. There are a couple of calling places missing in your patch. With them it works nicely. Maybe moving update_cond_flag() inside trace_event_trigger_enable_disable() would be an option?
cheers, daniel
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 4d8f5df..221ab1f 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -1471,11 +1471,12 @@ static int hist_register_trigger(char *glob, struct event_trigger_ops *ops, list_add_rcu(&data->list, &file->triggers); ret++; + update_cond_flag(file); if (trace_event_trigger_enable_disable(file, 1) < 0) { list_del_rcu(&data->list); + update_cond_flag(file); ret--; } - update_cond_flag(file); out: return ret; } diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c index 8c8f2ee..e47a229 100644 --- a/kernel/trace/trace_events_trigger.c +++ b/kernel/trace/trace_events_trigger.c @@ -1264,6 +1264,7 @@ int event_enable_trigger_func(struct event_command *cmd_ops, goto out_free; } + update_cond_flag(file); ret = trace_event_enable_disable(event_enable_file, 1, 1); if (ret < 0) goto out_put; @@ -1286,6 +1287,7 @@ int event_enable_trigger_func(struct event_command *cmd_ops, out_disable: trace_event_enable_disable(event_enable_file, 0, 1); out_put: + update_cond_flag(file); module_put(event_enable_file->event_call->mod); out_free: if (cmd_ops->set_filter)
> Tom > > [PATCH] tracing: Update cond flag before enabling or disabling a trigger > > Before a trigger is enabled, the cond flag should be set beforehand, > otherwise an trigger that's expecting to process a trace record > (e.g. one with post_trigger set) could be invoked without one. > > Likewise a trigger's cond flag should be reset after it's disabled, > not before. > > Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com> > --- > kernel/trace/trace_events_trigger.c | 10 ++++++---- > 1 file changed, 6 insertions(+), 4 deletions(-) > > diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c > index 7105f15..108e46c 100644 > --- a/kernel/trace/trace_events_trigger.c > +++ b/kernel/trace/trace_events_trigger.c > @@ -546,11 +546,12 @@ static int register_trigger(char *glob, struct event_trigger_ops *ops, > list_add_rcu(&data->list, &file->triggers); > ret++; > > + update_cond_flag(file); > if (trace_event_trigger_enable_disable(file, 1) < 0) { > list_del_rcu(&data->list); > + update_cond_flag(file); > ret--; > } > - update_cond_flag(file); > out: > return ret; > } > @@ -578,8 +579,8 @@ void unregister_trigger(char *glob, struct event_trigger_ops *ops, > if (data->cmd_ops->trigger_type == test->cmd_ops->trigger_type) { > unregistered = true; > list_del_rcu(&data->list); > - update_cond_flag(file); > trace_event_trigger_enable_disable(file, 0); > + update_cond_flag(file); > break; > } > } > @@ -1324,11 +1325,12 @@ int event_enable_register_trigger(char *glob, > list_add_rcu(&data->list, &file->triggers); > ret++; > > + update_cond_flag(file); > if (trace_event_trigger_enable_disable(file, 1) < 0) { > list_del_rcu(&data->list); > + update_cond_flag(file); > ret--; > } > - update_cond_flag(file); > out: > return ret; > } > @@ -1351,8 +1353,8 @@ void event_enable_unregister_trigger(char *glob, > (enable_data->file == test_enable_data->file)) { > unregistered = true; > list_del_rcu(&data->list); > - update_cond_flag(file); > trace_event_trigger_enable_disable(file, 0); > + update_cond_flag(file); > break; > } > } >
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