Messages in this thread | | | Date | Mon, 17 Jun 2019 19:45:14 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH 3/3] tracing: Add 2 new funcs. for kernel access to Ftrace instances. |
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On Wed, 12 Jun 2019 09:34:19 -0700 Divya Indi <divya.indi@oracle.com> wrote:
> Adding 2 new functions - > 1) trace_array_lookup : Look up and return a trace array, given its > name. > 2) trace_array_set_clr_event : Enable/disable event recording to the > given trace array. > > Newly added functions trace_array_lookup and trace_array_create also > need to increment the reference counter associated with the trace array > they return. This is to ensure the trace array does not get freed > while in use by the newly introduced APIs. > The reference ctr is decremented in the trace_array_destroy. > > Signed-off-by: Divya Indi <divya.indi@oracle.com> > --- > include/linux/trace_events.h | 3 +++ > kernel/trace/trace.c | 30 +++++++++++++++++++++++++++++- > kernel/trace/trace_events.c | 22 ++++++++++++++++++++++ > 3 files changed, 54 insertions(+), 1 deletion(-) > > diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h > index d7b7d85..0cc99a8 100644 > --- a/include/linux/trace_events.h > +++ b/include/linux/trace_events.h > @@ -545,7 +545,10 @@ int trace_array_printk(struct trace_array *tr, unsigned long ip, > struct trace_array *trace_array_create(const char *name); > int trace_array_destroy(struct trace_array *tr); > int ftrace_set_clr_event(struct trace_array *tr, char *buf, int set); > +struct trace_array *trace_array_lookup(const char *name); > int trace_set_clr_event(const char *system, const char *event, int set); > +int trace_array_set_clr_event(struct trace_array *tr, const char *system, > + const char *event, int set); > > /* > * The double __builtin_constant_p is because gcc will give us an error > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index a60dc13..fb70ccc 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -8364,6 +8364,8 @@ struct trace_array *trace_array_create(const char *name) > > list_add(&tr->list, &ftrace_trace_arrays); > > + tr->ref++; > +
Needs a comment for why the ref is incremented.
> mutex_unlock(&trace_types_lock); > mutex_unlock(&event_mutex); > > @@ -8385,7 +8387,14 @@ struct trace_array *trace_array_create(const char *name) > > static int instance_mkdir(const char *name) > { > - return PTR_ERR_OR_ZERO(trace_array_create(name)); > + struct trace_array *tr; > + > + tr = trace_array_create(name); > + if (IS_ERR(tr)) > + return PTR_ERR(tr); > + trace_array_put(tr);
Need a comment to why we need to do a put here.
> + > + return 0; > } > > static int __remove_instance(struct trace_array *tr) > @@ -8434,6 +8443,7 @@ int trace_array_destroy(struct trace_array *tr) > mutex_lock(&event_mutex); > mutex_lock(&trace_types_lock); > > + tr->ref--; > ret = __remove_instance(tr); > > mutex_unlock(&trace_types_lock); > @@ -8465,6 +8475,24 @@ static int instance_rmdir(const char *name) > return ret; > } >
Need a kerneldoc heading here, that also states that if a trace_array is returned, it requires a call to trace_array_put().
> +struct trace_array *trace_array_lookup(const char *name) > +{ > + struct trace_array *tr; > + > + mutex_lock(&trace_types_lock); > + > + list_for_each_entry(tr, &ftrace_trace_arrays, list) { > + if (tr->name && strcmp(tr->name, name) == 0) { > + tr->ref++; > + mutex_unlock(&trace_types_lock); > + return tr; > + } > + } > + mutex_unlock(&trace_types_lock); > + return NULL; > +} > +EXPORT_SYMBOL_GPL(trace_array_lookup); > + > static __init void create_trace_instances(struct dentry *d_tracer) > { > trace_instance_dir = tracefs_create_instance_dir("instances", d_tracer, > diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c > index 445b059..c126d2c 100644 > --- a/kernel/trace/trace_events.c > +++ b/kernel/trace/trace_events.c > @@ -859,6 +859,28 @@ int trace_set_clr_event(const char *system, const char *event, int set) > } > EXPORT_SYMBOL_GPL(trace_set_clr_event); > > +/** > + * trace_array_set_clr_event - enable or disable an event for a trace array > + * @system: system name to match (NULL for any system) > + * @event: event name to match (NULL for all events, within system) > + * @set: 1 to enable, 0 to disable > + * > + * This is a way for other parts of the kernel to enable or disable > + * event recording to instances. > + * > + * Returns 0 on success, -EINVAL if the parameters do not match any > + * registered events. > + */ > +int trace_array_set_clr_event(struct trace_array *tr, const char *system, > + const char *event, int set) > +{ > + if (!tr) > + return -ENODEV;
If we have this, should we get rid of the external use of ftrace_set_clr_event()?
-- Steve
> + > + return __ftrace_set_clr_event(tr, NULL, system, event, set); > +} > +EXPORT_SYMBOL_GPL(trace_array_set_clr_event); > + > /* 128 should be much more than enough */ > #define EVENT_BUF_SIZE 127 >
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