Messages in this thread | | | Subject | Re: [PATCH v4 3/4] tracing: Add helper functions to simplify event_command.parse() callback handling | From | Tom Zanussi <> | Date | Mon, 13 Dec 2021 14:21:19 -0600 |
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Hi Masami,
On Mon, 2021-12-13 at 22:46 +0900, Masami Hiramatsu wrote: > Hi Tom, > > On Fri, 10 Dec 2021 15:16:24 -0600 > Tom Zanussi <zanussi@kernel.org> wrote: > > > +/* > > + * Event trigger parsing helper functions. > > + * > > + * These functions help make it easier to write an event trigger > > + * parsing function i.e. the struct event_command.parse() callback > > + * function responsible for parsing and registering a trigger > > command > > + * written to the 'trigger' file. > > + * > > + * A trigger command (or just 'trigger' for short) takes the form: > > + * [trigger] [if filter] > > + * > > + * The struct event_command.parse() callback (and other struct > > + * event_command functions) refer to several components of a > > trigger > > + * command. Those same components are referenced by the event > > trigger > > + * parsing helper functions defined below. These components are: > > + * > > + * cmd - the trigger command name > > + * glob - the trigger command name optionally prefaced with > > '!' > > + * param - text remaining after the command is stripped of cmd > > and ':' > > + * filter - the optional filter text following (and including) > > 'if' > > + * > > + * To illustrate the use of these componenents, here are some > > concrete > > + * examples. For the following triggers: > > + * > > + * echo 'traceon:5 if pid == 0' > trigger > > + * - 'traceon' is both cmd and glob > > + * - '5 if pid == 0' is the param > > + * - 'if pid == 0' is the filter > > I would like to know why both 'param' and 'filter' has "if pid == 0". > I thought that part is (generic) filter and not a parameter. > > If I missed any discussion on this point, sorry about that.
No discussion about this in particular, but from Steve's review I did change 'param' to 'param_and_filter' in the code. So I guess I should change these to strip the filter from the param when describing them, and then it's obvious that param_and_filter refers to the combination. I'll change that in the next version.
> > > + * > > + * echo 'enable_event:sys:event:n' > trigger > > + * - 'enable_event' is both cmd and glob > > + * - 'sys:event:n' is the param > > + * - there is no filter > > + * > > + * echo 'hist:keys=pid if prio > 50' > trigger > > + * - 'hist' is both cmd and glob > > + * - 'keys=pid if prio > 50' is the param > > + * - 'if prio > 50' is the filter > > + * > > + * echo '!enable_event:sys:event:n' > trigger > > + * - 'enable_event' the cmd > > + * - '!enable_event' is the glob > > + * - 'sys:event:n' is the param > > + * - there is no filter > > + * > > + * echo 'traceoff' > trigger > > + * - 'traceoff' is both cmd and glob > > + * - there is no param > > + * - there is no filter > > + * > > + * 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(const char *glob) > > +{ > > + 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(const char *param) > > +{ > > + return !param; > > +} > > + > > +/** > > + * event_trigger_separate_filter - separate an event trigger from > > a filter > > + * @param: The param string containing trigger and possibly filter > > + * @trigger: outparam, will be filled with a pointer to the > > trigger > > + * @filter: outparam, will be filled with a pointer to the filter > > + * @param_required: Specifies whether or not the param string is > > required > > + * > > + * 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 *filter. Either the > > *trigger > > + * or the *filter 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. > > + * > > + * Return: 0 on success, errno otherwise > > + */ > > +int event_trigger_separate_filter(char *param_and_filter, char > > **param, > > + char **filter, bool param_required) > > +{ > > + int ret = 0; > > + > > + *param = *filter = NULL; > > + > > + if (!param_and_filter) { > > + if (param_required) > > + ret = -EINVAL; > > + goto out; > > + } > > + > > + /* > > + * Here we check for an optional param. The only legal > > + * optional param is :n, and if that's the case, continue > > + * below. Otherwise we assume what's left is a filter and > > + * return it as the filter string for the caller to deal with. > > + */ > > + if (!param_required && param_and_filter && > > !isdigit(param_and_filter[0])) { > > + *filter = param_and_filter; > > + goto out; > > + } > > + > > + /* > > + * Separate the param from the filter (param [if filter]). > > + * Here we have either an optional :n param or a required > > + * param and an optional filter. > > + */ > > + *param = strsep(¶m_and_filter, " \t"); > > + if (!*param) { > > + ret = -EINVAL; > > This seems not happen because this means "!param_and_filter" and > that is already checked at the entry of this function.
Yes, I think you're correct. I can just remove that check.
> > > + goto out; > > + } > > + > > + /* > > + * Here we have a filter, though it may be empty. > > + */ > > + if (param_and_filter) { > > + *filter = skip_spaces(param_and_filter); > > + if (!**filter) > > + *filter = 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 > > Does this mean trigger parameter?
Yes, I'll change this to 'param'.
> > > + * @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; > > +} > > Does this work with '!enable_event:sys:event:n' case? > (we need to find the last parameter.)
Yes, because :n isn't used in that case. Since you can't have multiple 'enable_event:sys:event:n' where sys:event are the same, whether using :n or not, it suffices for delete to use only sys:event and ignore :n.
Thanks,
Tom
> > Thank you, > >
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