As per Linux Kernel documentation guidelines
(https://docs.kernel.org/doc-guide/kernel-doc.html),
<<Every function that is exported to loadable modules using
EXPORT_SYMBOL or EXPORT_SYMBOL_GPL should have a kernel-doc
comment>>; hence this patch adds detailed kernel-doc headers
documentation for trace_array_set_clr_event, trace_set_clr_event
and the main functions in the respective call-trees that support
their functionalities.
For each of the documented functions, as part of the extensive
description, a set of "Function's expectations" are described in
a way that facilitate:
1) evaluating the current code and any proposed modification
to behave as described;
2) writing kernel tests to verify the code to behave as described.
Signed-off-by: Gabriele Paoloni <gpaol...@redhat.com>
---
Re-sending as no feedbacks have been received.
---
kernel/trace/trace_events.c | 125 +++++++++++++++++++++++++++++++-----
1 file changed, 109 insertions(+), 16 deletions(-)
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 120531268abf..4bd1f6e73ef1 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -763,6 +763,54 @@ void trace_event_enable_tgid_record(bool enable)
} while_for_each_event_file();
}
+/*
+ * __ftrace_event_enable_disable - enable or disable a trace event
+ * @file: trace event file associated with the event.
+ * @enable: 0 or 1 respectively to disable/enable the event (any other value is
+ * invalid).
+ * @soft_disable: 1 or 0 respectively to mark if the enable parameter IS or
+ * IS NOT a soft enable/disable.
+ *
+ * Function's expectations:
+ * - If soft_disable is 1 a reference counter associated with the trace
+ * event shall be increased or decreased according to the enable parameter
+ * being 1 (enable) or 0 (disable) respectively.
+ * If the reference counter is > 0 before the increase or after the decrease,
+ * no other actions shall be taken.
+ *
+ * - if soft_disable is 1 and the trace event reference counter is 0 before
+ * the increase or after the decrease, an enable value set to 0 or 1 shall set
+ * or clear the soft mode flag respectively; this is characterized by disabling
+ * or enabling the use of trace_buffered_event respectively.
+ *
+ * - If soft_disable is 1 and enable is 0 and the reference counter reaches
+ * zero and if the soft disabled flag is set (i.e. if the event was previously
+ * enabled with soft_disable = 1), tracing for the trace point event shall be
+ * disabled and the soft disabled flag shall be cleared.
+ *
+ * - If soft_disable is 0 and enable is 0, tracing for the trace point event
+ * shall be disabled only if the soft mode flag is clear (i.e. event previously
+ * enabled with soft_disable = 0). Additionally the soft disabled flag shall be
+ * set or cleared according to the soft mode flag being set or clear
+ * respectively.
+ *
+ * - If enable is 1, tracing for the trace point event shall be enabled (if
+ * previously disabled); in addition if soft_disable is 1 and the reference
+ * counter is 0 before the increase, the soft disabled flag shall be set.
+ *
+ * - When enabling or disabling tracing for the trace point event
+ * the flags associated with comms and tgids shall be checked and, if set,
+ * respectively tracing of comms and tgdis at sched_switch shall be
+ * enabled/disabled.
+ *
+ * Returns 0 on success, or any error returned by the event register or
+ * unregister callbacks.
+ *
+ * NOTE: in order to invoke this code in a thread-safe way, event_mutex shall
+ * be locked before calling it.
+ * NOTE: the validity of the input pointer file shall be checked by the caller
+ *
+ */
static int __ftrace_event_enable_disable(struct trace_event_file *file,
int enable, int soft_disable)
{
@@ -1296,7 +1344,37 @@ static void remove_event_file_dir(struct
trace_event_file *file)
}
/*
- * __ftrace_set_clr_event(NULL, NULL, NULL, set) will set/unset all events.
+ * __ftrace_set_clr_event_nolock - enable or disable an event within a system
+ * (thread-unsafe).
+ * @tr: target trace_array containing the events list (shall be a non-NULL
+ * valid pointer).
+ * @match: target system or event name (NULL for any).
+ * @sub: target system name (NULL for any).
+ * @event: target event name (NULL for any).
+ * @set: 1 to enable, 0 to disable (any other value is invalid).
+ * @mod: target module name (NULL for any).
+ *
+ * Function's expectations:
+ * - If mod is set, the mod name shall be sanitized by replacing all '-' with
+ * '_' to match the modules' naming convention used in the Kernel.
+ * - From the events' list in the input tr, the ensemble of events to be
enabled
+ * or disabled shall be selected according to the input match, sub, event and
+ * mod parameters. Each of these parameters, if set, shall restrict the
events
+ * ensemble to those with a matching parameter's name.
+ * - For each of the selected events the IGNORE_ENABLE flag shall be checked,
+ * and, if not set, ftrace_event_enable_disable shall be invoked passing the
+ * input set parameter to either enable or disable the event.
+ *
+ * Returns 0 on success, -EINVAL if the parameters do not match any registered
+ * events, -ENOMEM if memory allocation fails for the module pointer or the
+ * error condition returned by the first call to ftrace_event_enable_disable
+ * that returned an error.
+ *
+ * NOTE: in order to invoke this code in a thread-safe way, event_mutex shall
+ * be locked before calling it.
+ * NOTE: the validity of the input pointer tr shall be checked by the caller.
+ * NOTE: __ftrace_set_clr_event_nolock(NULL, NULL, NULL, set, NULL) will
+ * set/unset all events.
*/
static int
__ftrace_set_clr_event_nolock(struct trace_array *tr, const char *match,
@@ -1439,16 +1517,24 @@ int ftrace_set_clr_event(struct trace_array *tr, char
*buf, int set)
}
/**
- * trace_set_clr_event - enable or disable an event
- * @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
+ * trace_set_clr_event - enable or disable an event within a system.
+ * @system: system name (NULL for any system).
+ * @event: event name (NULL for all events, within system).
+ * @set: 1 to enable, 0 to disable (any other value is invalid).
*
* 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.
+ * Function's expectations:
+ * - This function shall retrieve the pointer of the global trace array (global
+ * tracer) and pass it, along the rest of input parameters, to
+ * __ftrace_set_clr_event_nolock.
+ * - This function shall properly lock/unlock the global event_mutex
+ * before/after invoking ftrace_set_clr_event_nolock.
+ *
+ * Returns 0 on success, -ENODEV if the global tracer cannot be retrieved,
+ * -EINVAL if the parameters do not match any registered events, any other
+ * error condition returned by __ftrace_set_clr_event_nolock.
*/
int trace_set_clr_event(const char *system, const char *event, int set)
{
@@ -1462,17 +1548,24 @@ 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
+ * trace_array_set_clr_event - enable or disable an event within a system for
+ * a trace array.
+ * @tr: input trace array.
+ * @system: system name (NULL for any system).
+ * @event: event name (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.
+ * This is a way for other parts of the kernel to enable or disable event
+ * recording.
+ *
+ * Function's expectations:
+ * - This function shall properly lock/unlock the global event_mutex
+ * before/after invoking ftrace_set_clr_event_nolock passing along the same
+ * input parameters.
*
- * Returns 0 on success, -EINVAL if the parameters do not match any
- * registered events.
+ * Returns 0 on success, -ENOENT if the input tr is NULL, -EINVAL if the
+ * parameters do not match any registered events, any other error condition
+ * returned by __ftrace_set_clr_event_nolock.
*/
int trace_array_set_clr_event(struct trace_array *tr, const char *system,
const char *event, bool enable)
--
2.48.1
