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Message-Id: <20191123181241.684687713@goodmis.org>
Date: Sat, 23 Nov 2019 13:12:04 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: linux-kernel@...r.kernel.org
Cc: Ingo Molnar <mingo@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Divya Indi <divya.indi@...cle.com>,
Aruna Ramakrishna <aruna.ramakrishna@...cle.com>
Subject: [for-next][PATCH 07/10] tracing: Adding new functions for kernel access to Ftrace instances
From: Divya Indi <divya.indi@...cle.com>
Adding 2 new functions -
1) struct trace_array *trace_array_get_by_name(const char *name);
Return pointer to a trace array with given name. If it does not exist,
create and return pointer to the new trace array.
2) int trace_array_set_clr_event(struct trace_array *tr,
const char *system ,const char *event, bool enable);
Enable/Disable events to this trace array.
Additionally,
- To handle reference counters, export trace_array_put()
- Due to introduction of the above 2 new functions, we no longer need to
export - ftrace_set_clr_event & trace_array_create APIs.
Link: http://lkml.kernel.org/r/1574276919-11119-2-git-send-email-divya.indi@oracle.com
Signed-off-by: Divya Indi <divya.indi@...cle.com>
Reviewed-by: Aruna Ramakrishna <aruna.ramakrishna@...cle.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
include/linux/trace.h | 3 +-
include/linux/trace_events.h | 3 +-
kernel/trace/trace.c | 96 ++++++++++++++++++++++++++++--------
kernel/trace/trace.h | 1 -
kernel/trace/trace_events.c | 27 +++++++++-
5 files changed, 106 insertions(+), 24 deletions(-)
diff --git a/include/linux/trace.h b/include/linux/trace.h
index 24fcf07812ae..7fd86d3c691f 100644
--- a/include/linux/trace.h
+++ b/include/linux/trace.h
@@ -29,7 +29,8 @@ struct trace_array;
void trace_printk_init_buffers(void);
int trace_array_printk(struct trace_array *tr, unsigned long ip,
const char *fmt, ...);
-struct trace_array *trace_array_create(const char *name);
+void trace_array_put(struct trace_array *tr);
+struct trace_array *trace_array_get_by_name(const char *name);
int trace_array_destroy(struct trace_array *tr);
#endif /* CONFIG_TRACING */
diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index 60a41b7069dd..4c6e15605766 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -555,7 +555,8 @@ extern int trace_event_get_offsets(struct trace_event_call *call);
int ftrace_set_clr_event(struct trace_array *tr, char *buf, int set);
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, bool enable);
/*
* The double __builtin_constant_p is because gcc will give us an error
* if we try to allocate the static variable to fmt if it is not a
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 42659ce6ac0c..02a23a6e5e00 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -301,12 +301,24 @@ static void __trace_array_put(struct trace_array *this_tr)
this_tr->ref--;
}
+/**
+ * trace_array_put - Decrement the reference counter for this trace array.
+ *
+ * NOTE: Use this when we no longer need the trace array returned by
+ * trace_array_get_by_name(). This ensures the trace array can be later
+ * destroyed.
+ *
+ */
void trace_array_put(struct trace_array *this_tr)
{
+ if (!this_tr)
+ return;
+
mutex_lock(&trace_types_lock);
__trace_array_put(this_tr);
mutex_unlock(&trace_types_lock);
}
+EXPORT_SYMBOL_GPL(trace_array_put);
int tracing_check_open_get_tr(struct trace_array *tr)
{
@@ -8437,24 +8449,15 @@ static void update_tracer_options(struct trace_array *tr)
mutex_unlock(&trace_types_lock);
}
-struct trace_array *trace_array_create(const char *name)
+static struct trace_array *trace_array_create(const char *name)
{
struct trace_array *tr;
int ret;
- mutex_lock(&event_mutex);
- mutex_lock(&trace_types_lock);
-
- ret = -EEXIST;
- list_for_each_entry(tr, &ftrace_trace_arrays, list) {
- if (tr->name && strcmp(tr->name, name) == 0)
- goto out_unlock;
- }
-
ret = -ENOMEM;
tr = kzalloc(sizeof(*tr), GFP_KERNEL);
if (!tr)
- goto out_unlock;
+ return ERR_PTR(ret);
tr->name = kstrdup(name, GFP_KERNEL);
if (!tr->name)
@@ -8499,8 +8502,8 @@ struct trace_array *trace_array_create(const char *name)
list_add(&tr->list, &ftrace_trace_arrays);
- mutex_unlock(&trace_types_lock);
- mutex_unlock(&event_mutex);
+ tr->ref++;
+
return tr;
@@ -8510,24 +8513,77 @@ struct trace_array *trace_array_create(const char *name)
kfree(tr->name);
kfree(tr);
- out_unlock:
- mutex_unlock(&trace_types_lock);
- mutex_unlock(&event_mutex);
-
return ERR_PTR(ret);
}
-EXPORT_SYMBOL_GPL(trace_array_create);
static int instance_mkdir(const char *name)
{
- return PTR_ERR_OR_ZERO(trace_array_create(name));
+ struct trace_array *tr;
+ int ret;
+
+ mutex_lock(&event_mutex);
+ mutex_lock(&trace_types_lock);
+
+ ret = -EEXIST;
+ list_for_each_entry(tr, &ftrace_trace_arrays, list) {
+ if (tr->name && strcmp(tr->name, name) == 0)
+ goto out_unlock;
+ }
+
+ tr = trace_array_create(name);
+
+ ret = PTR_ERR_OR_ZERO(tr);
+
+out_unlock:
+ mutex_unlock(&trace_types_lock);
+ mutex_unlock(&event_mutex);
+ return ret;
+}
+
+/**
+ * trace_array_get_by_name - Create/Lookup a trace array, given its name.
+ * @name: The name of the trace array to be looked up/created.
+ *
+ * Returns pointer to trace array with given name.
+ * NULL, if it cannot be created.
+ *
+ * NOTE: This function increments the reference counter associated with the
+ * trace array returned. This makes sure it cannot be freed while in use.
+ * Use trace_array_put() once the trace array is no longer needed.
+ *
+ */
+struct trace_array *trace_array_get_by_name(const char *name)
+{
+ struct trace_array *tr;
+
+ mutex_lock(&event_mutex);
+ mutex_lock(&trace_types_lock);
+
+ list_for_each_entry(tr, &ftrace_trace_arrays, list) {
+ if (tr->name && strcmp(tr->name, name) == 0)
+ goto out_unlock;
+ }
+
+ tr = trace_array_create(name);
+
+ if (IS_ERR(tr))
+ tr = NULL;
+out_unlock:
+ if (tr)
+ tr->ref++;
+
+ mutex_unlock(&trace_types_lock);
+ mutex_unlock(&event_mutex);
+ return tr;
}
+EXPORT_SYMBOL_GPL(trace_array_get_by_name);
static int __remove_instance(struct trace_array *tr)
{
int i;
- if (tr->ref || (tr->current_trace && tr->current_trace->ref))
+ /* Reference counter for a newly created trace array = 1. */
+ if (tr->ref > 1 || (tr->current_trace && tr->current_trace->ref))
return -EBUSY;
list_del(&tr->list);
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 2df8aed6a8f0..ca7fccafbcbb 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -345,7 +345,6 @@ extern struct list_head ftrace_trace_arrays;
extern struct mutex trace_types_lock;
extern int trace_array_get(struct trace_array *tr);
-extern void trace_array_put(struct trace_array *tr);
extern int tracing_check_open_get_tr(struct trace_array *tr);
extern int tracing_set_time_stamp_abs(struct trace_array *tr, bool abs);
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 2a3ac2365445..6b3a69e9aa6a 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -827,7 +827,6 @@ int ftrace_set_clr_event(struct trace_array *tr, char *buf, int set)
return ret;
}
-EXPORT_SYMBOL_GPL(ftrace_set_clr_event);
/**
* trace_set_clr_event - enable or disable an event
@@ -852,6 +851,32 @@ 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.
+ * @tr: concerned trace array.
+ * @system: system name to match (NULL for any system)
+ * @event: event name to match (NULL for all events, within system)
+ * @enable: true to enable, false to disable
+ *
+ * This is a way for other parts of the kernel to enable or disable
+ * event recording.
+ *
+ * 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, bool enable)
+{
+ int set;
+
+ if (!tr)
+ return -ENOENT;
+
+ set = (enable == true) ? 1 : 0;
+ 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
--
2.24.0
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