Messages in this thread | | | Subject | Re: [PATCH v3 1/2] tracing: Add helper functions to simplify event_command callback handling | From | Tom Zanussi <> | Date | Tue, 30 Nov 2021 17:10:05 -0600 |
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Hi Steve,
On Tue, 2021-11-30 at 16:46 -0500, Steven Rostedt wrote: > On Tue, 23 Nov 2021 14:53:53 -0600 > Tom Zanussi <zanussi@kernel.org> wrote: > > > The event_command.func() callback is responsible for parsing and > > registering triggers. The existing command implementions for this > > callback duplicate a lot of the same code, so to clean up and > > consolidate those implementations, introduce a handful of helper > > functions for implementors to use. > > > > This also makes it easier for new commands to be implemented and > > allows them to focus more on the customizations they provide rather > > than obscuring and complicating it with boilerplate code. > > > > Signed-off-by: Tom Zanussi <zanussi@kernel.org> > > Thanks for the update Tom! > > > --- > > kernel/trace/trace.h | 23 +++ > > kernel/trace/trace_events_trigger.c | 286 > > ++++++++++++++++++++++++++++ > > 2 files changed, 309 insertions(+) > > > > diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h > > index 6b60ab9475ed..66cc32aca2e8 100644 > > --- a/kernel/trace/trace.h > > +++ b/kernel/trace/trace.h > > @@ -1594,6 +1594,29 @@ get_named_trigger_data(struct > > event_trigger_data *data); > > extern int register_event_command(struct event_command *cmd); > > extern int unregister_event_command(struct event_command *cmd); > > extern int register_trigger_hist_enable_disable_cmds(void); > > +extern bool event_trigger_check_remove(char *cmd); > > +extern bool event_trigger_empty_param(char *param); > > +extern int event_trigger_separate_filter(char **trigger, char > > **param, bool param_required); > > +extern struct event_trigger_data * > > +event_trigger_alloc(struct event_command *cmd_ops, > > + char *cmd, > > + char *param, > > + void *private_data); > > +extern int event_trigger_parse_num(char *trigger, > > + struct event_trigger_data > > *trigger_data); > > +extern int event_trigger_set_filter(struct event_command *cmd_ops, > > + struct trace_event_file *file, > > + char *param, > > + struct event_trigger_data > > *trigger_data); > > +extern void event_trigger_reset_filter(struct event_command > > *cmd_ops, > > + struct event_trigger_data > > *trigger_data); > > +extern int event_trigger_register(struct event_command *cmd_ops, > > + struct trace_event_file *file, > > + char *glob, > > + char *cmd, > > + char *trigger, > > + struct event_trigger_data > > *trigger_data, > > + int *n_registered); > > > > /** > > * struct event_trigger_ops - callbacks for trace event triggers > > diff --git a/kernel/trace/trace_events_trigger.c > > b/kernel/trace/trace_events_trigger.c > > index 3d5c07239a2a..a873f4e8be04 100644 > > --- a/kernel/trace/trace_events_trigger.c > > +++ b/kernel/trace/trace_events_trigger.c > > @@ -621,6 +621,292 @@ static void unregister_trigger(char *glob, > > struct event_trigger_ops *ops, > > data->ops->free(data->ops, data); > > } > > > > +/* > > + * Event trigger parsing helper functions. > > + * > > + * These functions help make it easier to write an event trigger > > + * parsing function i.e. the struct event_command.func() callback > > + * function responsible for parsing and registering a trigger > > command > > + * written to the 'trigger' file. > > + * > > + * There are a few different categories of event trigger covered > > by > > + * these helpers: > > + * > > + * - triggers that don't require a parameter e.g. traceon > > + * - triggers that do require a parameter e.g. enable_event and > > hist > > + * - triggers that though they may not require a param may > > support an > > + * optional 'n' param (n = number of times the trigger should > > fire) > > + * e.g.: traceon:5 or enable_event:sys:event:n > > + * - triggers that do not support an 'n' param e.g. hist > > + * > > + * These functions can be used or ignored as necessary - it all > > + * depends on the complexity of the trigger, and the granularity > > of > > + * the functions supported reflects the fact that some > > implementations > > + * may need to customize certain aspects of their implementations > > and > > + * won't need certain functions. For instance, the hist trigger > > + * implementation doesn't use event_trigger_separate_filter() > > because > > + * it has special requirements for handling the filter. > > + */ > > + > > +/** > > + * event_trigger_check_remove - check whether an event trigger > > specifies remove > > + * @glob: The trigger command string, with optional remove(!) > > operator > > + * > > + * The event trigger callback implementations pass in 'glob' as a > > + * parameter. This is the command name either with or without a > > + * remove(!) operator. This function simply parses the glob and > > + * determines whether the command corresponds to a trigger removal > > or > > + * a trigger addition. > > + * > > + * Return: true if this is a remove command, false otherwise > > + */ > > +bool event_trigger_check_remove(char *glob) > > const char *glob ?
Yep, will change.
> > > +{ > > + return (glob && glob[0] == '!') ? true : false; > > +} > > + > > +/** > > + * event_trigger_empty_param - check whether the param is empty > > + * @param: The trigger param string > > + * > > + * The event trigger callback implementations pass in 'param' as a > > + * parameter. This corresponds to the string following the > > command > > + * name minus the command name. This function can be called by a > > + * callback implementation for any command that requires a param; > > a > > + * callback that doesn't require a param can ignore it. > > + * > > + * Return: true if this is an empty param, false otherwise > > + */ > > +bool event_trigger_empty_param(char *param) > > const char *param ?
Same.
> > +{ > > + return !param; > > +} > > + > > +/** > > + * event_trigger_separate_filter - separate an event trigger from > > a filter > > + * @trigger: outparam, will be filled with a pointer to the > > trigger > > + * @param: The param string, will contain the filter after this is > > called > > + * @param_required: Specifies whether or not the param string is > > required > > + * > > Let's not make this more confusing then it has to be. Let's pass in > the > input parameter as a separate value. Because I'm totally confused by > what > is an input and what is an output. > > (char *param, char **trigger, char **filter, .. > > ? >
Yes, this probably makes more sense, to highlight what the results are.
> > > + * Given a param string of the form '[trigger] [if filter]', this > > + * function separates the filter from the trigger and returns the > > + * trigger in *trigger and the filter in *param. Either the > > *trigger > > + * or the *param may be set to NULL by this function - if not set > > to > > + * NULL, they will contain strings corresponding to the trigger > > and > > + * filter. > > + * > > + * There are two cases that need to be handled with respect to the > > + * passed-in param: either the param is required, or it is not > > + * required. If @param_required is set, and there's no param, it > > will > > + * return -EINVAL. If @param_required is not set and there's a > > param > > + * that starts with a number, that corresponds to the case of a > > + * trigger with :n (n = number of times the trigger should fire) > > and > > + * the parsing continues normally; otherwise the function just > > returns > > + * and assumes param just contains a filter and there's nothing > > else > > + * to do. > > I'm not sure how the number is parsed here. > > Really, getting rid of having two different ops that are attached to > each > other should be cleaned up first. At least change their internal > names. > > We have: struct event_command that has > > int (*func)(struct event_command > *cmd_ops, > struct trace_event_file *file, > char *glob, char *cmd, char > *params); > > And > > struct event_trigger_ops *(*get_trigger_ops)(char *cmd, char > *param); > > Where it returns event_tigger_ops that has: > > void (*func)(struct event_trigger_data > *data, > struct trace_buffer *buffer, > void *rec, > struct ring_buffer_event *rbe); > > So when I see: ops->func() I have no clue what func that is! > > Let's first rename one of them, and that way it is easier to know > what is > going on. There's a lot of magic here that is hard to follow. >
Yeah, definitely too many generic-sounding funcs() around that don't help at all in understanding what they actually do. Will think of better names.
> > + * > > + * Return: 0 on success, errno otherwise > > + */ > > +int event_trigger_separate_filter(char **trigger, char **param, > > bool param_required) > > +{ > > + int ret = 0; > > + > > + *trigger = NULL; > > + > > + if (!*param) { > > + if (param_required) > > + ret = -EINVAL; > > + goto out; > > + } > > + > > + /* the only legal optional param is :n */ > > + if (!param_required && *param && !isdigit(*param[0])) > > + goto out; > > How does *param[0] end up pointing to a number? If it was: > > trigger:n if filter > > ? >
Well, the param being passed around actually doesn't contain the trigger - it's what remains after the 'trigger:' has been removed. So in the case of trigger:n, param starts with 'n', so this works as usual.
> The event_trigger_parse_num() is called after this. > > > + > > + /* separate the trigger from the filter (trigger [if filter]) > > */ > > + *trigger = strsep(param, " \t"); > > + if (!*trigger) { > > + ret = -EINVAL; > > + goto out; > > + } > > + > > + if (*param) { > > + *param = skip_spaces(*param); > > + if (!**param) > > + *param = NULL; > > + } > > +out: > > + return ret; > > +} > > + > > +/** > > + * event_trigger_alloc - allocate and init event_trigger_data for > > a trigger > > + * @cmd_ops: The event_command operations for the trigger > > + * @cmd: The cmd string > > + * @param: The param string > > + * @private_data: User data to associate with the event trigger > > + * > > + * Allocate an event_trigger_data instance and initialize it. The > > + * @cmd_ops are used along with the @cmd and @param to get the > > + * trigger_ops to assign to the event_trigger_data. @private_data > > can > > + * also be passed in and associated with the event_trigger_data. > > + * > > + * Use event_trigger_free() to free an event_trigger_data object. > > + * > > + * Return: The trigger_data object success, NULL otherwise > > + */ > > +struct event_trigger_data *event_trigger_alloc(struct > > event_command *cmd_ops, > > + char *cmd, > > + char *param, > > + void *private_data) > > +{ > > + struct event_trigger_data *trigger_data; > > + struct event_trigger_ops *trigger_ops; > > + > > + trigger_ops = cmd_ops->get_trigger_ops(cmd, param); > > + > > + trigger_data = kzalloc(sizeof(*trigger_data), GFP_KERNEL); > > + if (!trigger_data) > > + return NULL; > > + > > + trigger_data->count = -1; > > + trigger_data->ops = trigger_ops; > > + trigger_data->cmd_ops = cmd_ops; > > + trigger_data->private_data = private_data; > > + > > + INIT_LIST_HEAD(&trigger_data->list); > > + INIT_LIST_HEAD(&trigger_data->named_list); > > + RCU_INIT_POINTER(trigger_data->filter, NULL); > > + > > + return trigger_data; > > +} > > + > > +/** > > + * event_trigger_parse_num - parse and return the number param for > > a trigger > > + * @trigger: The trigger string > > + * @trigger_data: The trigger_data for the trigger > > + * > > + * Parse the :n (n = number of times the trigger should fire) > > param > > + * and set the count variable in the trigger_data to the parsed > > count. > > + * > > + * Return: 0 on success, errno otherwise > > + */ > > +int event_trigger_parse_num(char *trigger, > > + struct event_trigger_data *trigger_data) > > +{ > > + char *number; > > + int ret = 0; > > + > > + if (trigger) { > > + number = strsep(&trigger, ":"); > > + > > + if (!strlen(number)) > > + return -EINVAL; > > + > > + /* > > + * We use the callback data field (which is a pointer) > > + * as our counter. > > + */ > > + ret = kstrtoul(number, 0, &trigger_data->count); > > + } > > + > > + return ret; > > +} > > + > > +/** > > + * event_trigger_set_filter - set an event trigger's filter > > + * @cmd_ops: The event_command operations for the trigger > > + * @file: The event file for the trigger's event > > + * @param: The string containing the filter > > + * @trigger_data: The trigger_data for the trigger > > + * > > + * Set the filter for the trigger. If the filter is NULL, just > > return > > + * without error. > > + * > > + * Return: 0 on success, errno otherwise > > + */ > > +int event_trigger_set_filter(struct event_command *cmd_ops, > > + struct trace_event_file *file, > > + char *param, > > + struct event_trigger_data *trigger_data) > > +{ > > + if (param && cmd_ops->set_filter) > > + return cmd_ops->set_filter(param, trigger_data, file); > > + > > + return 0; > > +} > > + > > +/** > > + * event_trigger_reset_filter - reset an event trigger's filter > > + * @cmd_ops: The event_command operations for the trigger > > + * @trigger_data: The trigger_data for the trigger > > + * > > + * Reset the filter for the trigger to no filter. > > + */ > > +void event_trigger_reset_filter(struct event_command *cmd_ops, > > + struct event_trigger_data > > *trigger_data) > > +{ > > + if (cmd_ops->set_filter) > > + cmd_ops->set_filter(NULL, trigger_data, NULL); > > +} > > + > > +/** > > + * event_trigger_register - register an event trigger > > + * @cmd_ops: The event_command operations for the trigger > > + * @file: The event file for the trigger's event > > + * @glob: The trigger command string, with optional remove(!) > > operator > > + * @cmd: The cmd string > > + * @param: The param string > > + * @trigger_data: The trigger_data for the trigger > > + * @n_registered: optional outparam, the number of triggers > > registered > > + * > > + * Register and event trigger. The @cmd_ops are used along with > > the > > "Register an event trigger"
Doh! Yeah, thanks for picking that up.
I'll create a new version with all these changes, thanks for your suggestions!
Tom
> > -- Steve > > > + * @cmd and @param to get the trigger_ops to pass to the > > + * cmd_ops->reg() function which actually does the registration. > > The > > + * cmd_ops->reg() function returns the number of triggers > > registered, > > + * which is assigned to n_registered, if n_registered is non-NULL. > > + * > > + * Return: 0 on success, errno otherwise > > + */ > > +int event_trigger_register(struct event_command *cmd_ops, > > + struct trace_event_file *file, > > + char *glob, > > + char *cmd, > > + char *param, > > + struct event_trigger_data *trigger_data, > > + int *n_registered) > > +{ > > + struct event_trigger_ops *trigger_ops; > > + int ret; > > + > > + if (n_registered) > > + *n_registered = 0; > > + > > + trigger_ops = cmd_ops->get_trigger_ops(cmd, param); > > + > > + ret = cmd_ops->reg(glob, trigger_ops, trigger_data, file); > > + /* > > + * The above returns on success the # of functions enabled, > > + * but if it didn't find any functions it returns zero. > > + * Consider no functions a failure too. > > + */ > > + if (!ret) { > > + cmd_ops->unreg(glob, trigger_ops, trigger_data, file); > > + ret = -ENOENT; > > + } else if (ret > 0) { > > + if (n_registered) > > + *n_registered = ret; > > + /* Just return zero, not the number of enabled > > functions */ > > + ret = 0; > > + } > > + > > + return ret; > > +} > > + > > +/* > > + * End event trigger parsing helper functions. > > + */ > > + > > /** > > * event_trigger_callback - Generic event_command @func > > implementation > > * @cmd_ops: The command ops, used for trigger registration > >
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