Hi Steven,
Thanks for taking the time to review. Please find my comments inline.
On 6/8/19 2:51 PM, Steven Rostedt wrote:
On Tue, 4 Jun 2019 17:42:05 -0700
Divya Indi <[email protected]> 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.
Signed-off-by: Divya Indi <[email protected]>
---
include/linux/trace_events.h | 3 +++
kernel/trace/trace.c | 11 +++++++++++
kernel/trace/trace_events.c | 22 ++++++++++++++++++++++
3 files changed, 36 insertions(+)
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..1d171fd 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -8465,6 +8465,17 @@ static int instance_rmdir(const char *name)
return ret;
}
+struct trace_array *trace_array_lookup(const char *name)
+{
+ struct trace_array *tr;
+ list_for_each_entry(tr, &ftrace_trace_arrays, list) {
Accessing the ftrace_trace_arrays requires taking the trace_types_lock.
It should also probably increment the ref counter too, and then
trace_array_put() needs to be called.
This prevents the trace array from being freed while something has
access to it.
-- Steve
Agree - Noted!
Also, adding a similar change for trace_array_create which also returns
a ptr to a newly created trace_array so will face the same issue.
Since trace_array_lookup and trace_array_create will be accompanied by a
trace_array_destroy once the use of the trace_array is done,
decrementing the reference ctr here.
Sending a v2 to address this.
Thanks,
Divya
+ if (tr->name && strcmp(tr->name, name) == 0)
+ return tr;
+ }
+ 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;
+
+ 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
