Re: [PATCH v2 3/3] perf parse-events: Print all errors

[James Clark]

On 31/01/2024 13:49, Ian Rogers wrote:
> Prior to this patch the first and the last error encountered during
> parsing are printed. To see other errors verbose needs
> enabling. Unfortunately this can drop useful errors, in particular on
> terms. This patch changes the errors so that instead of the first and
> last all errors are recorded and printed, the underlying data
> structure is changed to a list.
> 
> Before:
> ```
> $ perf stat -e 'slots/edge=2/' true
> event syntax error: 'slots/edge=2/'
>                                 \___ Bad event or PMU
> 
> Unable to find PMU or event on a PMU of 'slots'
> 
> Initial error:
> event syntax error: 'slots/edge=2/'
>                      \___ Cannot find PMU `slots'. Missing kernel support?
> Run 'perf list' for a list of valid events
> 
>  Usage: perf stat [<options>] [<command>]
> 
>     -e, --event <event>   event selector. use 'perf list' to list available events
> ```
> 
> After:
> ```
> $ perf stat -e 'slots/edge=2/' true
> event syntax error: 'slots/edge=2/'
>                      \___ Bad event or PMU
> 
> Unable to find PMU or event on a PMU of 'slots'
> 
> event syntax error: 'slots/edge=2/'
>                                 \___ value too big for format (edge), maximum is 1
> 
> event syntax error: 'slots/edge=2/'
>                      \___ Cannot find PMU `slots'. Missing kernel support?
> Run 'perf list' for a list of valid events
> 
>  Usage: perf stat [<options>] [<command>]
> 
>     -e, --event <event>   event selector. use 'perf list' to list available events
> ```
> 
> Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>

Reviewed-by: James Clark <james.clark@xxxxxxx>

> ---
> Prompted by discussion:
> https://lore.kernel.org/linux-perf-users/9dd303cb-0455-d8ac-ce0c-f4a8320b787b@xxxxxxx/
> ---
>  tools/perf/arch/x86/tests/hybrid.c |  5 +-
>  tools/perf/tests/expand-cgroup.c   |  3 +-
>  tools/perf/tests/parse-events.c    |  9 ++-
>  tools/perf/util/parse-events.c     | 92 ++++++++++++++++++------------
>  tools/perf/util/parse-events.h     | 14 ++---
>  tools/perf/util/parse-events.y     |  2 -
>  6 files changed, 67 insertions(+), 58 deletions(-)
> 
> diff --git a/tools/perf/arch/x86/tests/hybrid.c b/tools/perf/arch/x86/tests/hybrid.c
> index 40f5d17fedab..e221ea104174 100644
> --- a/tools/perf/arch/x86/tests/hybrid.c
> +++ b/tools/perf/arch/x86/tests/hybrid.c
> @@ -259,11 +259,10 @@ static int test_event(const struct evlist_test *e)
>  	parse_events_error__init(&err);
>  	ret = parse_events(evlist, e->name, &err);
>  	if (ret) {
> -		pr_debug("failed to parse event '%s', err %d, str '%s'\n",
> -			 e->name, ret, err.str);
> +		pr_debug("failed to parse event '%s', err %d\n", e->name, ret);
>  		parse_events_error__print(&err, e->name);
>  		ret = TEST_FAIL;
> -		if (strstr(err.str, "can't access trace events"))
> +		if (parse_events_error__contains(&err, "can't access trace events"))
>  			ret = TEST_SKIP;
>  	} else {
>  		ret = e->check(evlist);
> diff --git a/tools/perf/tests/expand-cgroup.c b/tools/perf/tests/expand-cgroup.c
> index 9c1a1f18db75..31966ff856f8 100644
> --- a/tools/perf/tests/expand-cgroup.c
> +++ b/tools/perf/tests/expand-cgroup.c
> @@ -127,8 +127,7 @@ static int expand_group_events(void)
>  	parse_events_error__init(&err);
>  	ret = parse_events(evlist, event_str, &err);
>  	if (ret < 0) {
> -		pr_debug("failed to parse event '%s', err %d, str '%s'\n",
> -			 event_str, ret, err.str);
> +		pr_debug("failed to parse event '%s', err %d\n", event_str, ret);
>  		parse_events_error__print(&err, event_str);
>  		goto out;
>  	}
> diff --git a/tools/perf/tests/parse-events.c b/tools/perf/tests/parse-events.c
> index fbdf710d5eea..feb5727584d1 100644
> --- a/tools/perf/tests/parse-events.c
> +++ b/tools/perf/tests/parse-events.c
> @@ -2506,11 +2506,10 @@ static int test_event(const struct evlist_test *e)
>  	parse_events_error__init(&err);
>  	ret = parse_events(evlist, e->name, &err);
>  	if (ret) {
> -		pr_debug("failed to parse event '%s', err %d, str '%s'\n",
> -			 e->name, ret, err.str);
> +		pr_debug("failed to parse event '%s', err %d\n", e->name, ret);
>  		parse_events_error__print(&err, e->name);
>  		ret = TEST_FAIL;
> -		if (err.str && strstr(err.str, "can't access trace events"))
> +		if (parse_events_error__contains(&err, "can't access trace events"))
>  			ret = TEST_SKIP;
>  	} else {
>  		ret = e->check(evlist);
> @@ -2535,8 +2534,8 @@ static int test_event_fake_pmu(const char *str)
>  	ret = __parse_events(evlist, str, /*pmu_filter=*/NULL, &err,
>  			     &perf_pmu__fake, /*warn_if_reordered=*/true);
>  	if (ret) {
> -		pr_debug("failed to parse event '%s', err %d, str '%s'\n",
> -			 str, ret, err.str);
> +		pr_debug("failed to parse event '%s', err %d\n",
> +			 str, ret);
>  		parse_events_error__print(&err, str);
>  	}
>  
> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> index 66eabcea4242..6f8b0fa17689 100644
> --- a/tools/perf/util/parse-events.c
> +++ b/tools/perf/util/parse-events.c
> @@ -2181,50 +2181,53 @@ int parse_event(struct evlist *evlist, const char *str)
>  	return ret;
>  }
>  
> +struct parse_events_error_entry {
> +	/** @list: The list the error is part of. */
> +	struct list_head list;
> +	/** @idx: index in the parsed string */
> +	int   idx;
> +	/** @str: string to display at the index */
> +	char *str;
> +	/** @help: optional help string */
> +	char *help;
> +};
> +
>  void parse_events_error__init(struct parse_events_error *err)
>  {
> -	bzero(err, sizeof(*err));
> +	INIT_LIST_HEAD(&err->list);
>  }
>  
>  void parse_events_error__exit(struct parse_events_error *err)
>  {
> -	zfree(&err->str);
> -	zfree(&err->help);
> -	zfree(&err->first_str);
> -	zfree(&err->first_help);
> +	struct parse_events_error_entry *pos, *tmp;
> +
> +	list_for_each_entry_safe(pos, tmp, &err->list, list) {
> +		zfree(&pos->str);
> +		zfree(&pos->help);
> +		list_del_init(&pos->list);
> +		free(pos);
> +	}
>  }
>  
>  void parse_events_error__handle(struct parse_events_error *err, int idx,
>  				char *str, char *help)
>  {
> +	struct parse_events_error_entry *entry;
> +
>  	if (WARN(!str || !err, "WARNING: failed to provide error string or struct\n"))
>  		goto out_free;
> -	switch (err->num_errors) {
> -	case 0:
> -		err->idx = idx;
> -		err->str = str;
> -		err->help = help;
> -		break;
> -	case 1:
> -		err->first_idx = err->idx;
> -		err->idx = idx;
> -		err->first_str = err->str;
> -		err->str = str;
> -		err->first_help = err->help;
> -		err->help = help;
> -		break;
> -	default:
> -		pr_debug("Multiple errors dropping message: %s (%s)\n",
> -			err->str, err->help ?: "<no help>");
> -		free(err->str);
> -		err->str = str;
> -		free(err->help);
> -		err->help = help;
> -		break;
> +
> +	entry = zalloc(sizeof(*entry));
> +	if (!entry) {
> +		pr_err("Failed to allocate memory for event parsing error: %s (%s)\n",
> +			str, help ?: "<no help>");
> +		goto out_free;
>  	}
> -	err->num_errors++;
> +	entry->idx = idx;
> +	entry->str = str;
> +	entry->help = help;
> +	list_add(&entry->list, &err->list);
>  	return;
> -
>  out_free:
>  	free(str);
>  	free(help);
> @@ -2294,19 +2297,34 @@ static void __parse_events_error__print(int err_idx, const char *err_str,
>  	}
>  }
>  
> -void parse_events_error__print(struct parse_events_error *err,
> +void parse_events_error__print(const struct parse_events_error *err,
>  			       const char *event)
>  {
> -	if (!err->num_errors)
> -		return;
> +	struct parse_events_error_entry *pos;
> +	bool first = true;
> +
> +	list_for_each_entry(pos, &err->list, list) {
> +		if (!first)
> +			fputs("\n", stderr);
> +		__parse_events_error__print(pos->idx, pos->str, pos->help, event);
> +		first = false;
> +	}
> +}
>  
> -	__parse_events_error__print(err->idx, err->str, err->help, event);
> +/*
> + * In the list of errors err, do any of the error strings (str) contain the
> + * given needle string?
> + */
> +bool parse_events_error__contains(const struct parse_events_error *err,
> +				  const char *needle)
> +{
> +	struct parse_events_error_entry *pos;
>  
> -	if (err->num_errors > 1) {
> -		fputs("\nInitial error:\n", stderr);
> -		__parse_events_error__print(err->first_idx, err->first_str,
> -					err->first_help, event);
> +	list_for_each_entry(pos, &err->list, list) {
> +		if (strstr(pos->str, needle) != NULL)
> +			return true;
>  	}
> +	return false;
>  }
>  
>  #undef MAX_WIDTH
> diff --git a/tools/perf/util/parse-events.h b/tools/perf/util/parse-events.h
> index 63c0a36a4bf1..809359e8544e 100644
> --- a/tools/perf/util/parse-events.h
> +++ b/tools/perf/util/parse-events.h
> @@ -130,13 +130,8 @@ struct parse_events_term {
>  };
>  
>  struct parse_events_error {
> -	int   num_errors;       /* number of errors encountered */
> -	int   idx;	/* index in the parsed string */
> -	char *str;      /* string to display at the index */
> -	char *help;	/* optional help string */
> -	int   first_idx;/* as above, but for the first encountered error */
> -	char *first_str;
> -	char *first_help;
> +	/** @list: The head of a list of errors. */
> +	struct list_head list;
>  };
>  
>  /* A wrapper around a list of terms for the sake of better type safety. */
> @@ -247,9 +242,10 @@ void parse_events_error__init(struct parse_events_error *err);
>  void parse_events_error__exit(struct parse_events_error *err);
>  void parse_events_error__handle(struct parse_events_error *err, int idx,
>  				char *str, char *help);
> -void parse_events_error__print(struct parse_events_error *err,
> +void parse_events_error__print(const struct parse_events_error *err,
>  			       const char *event);
> -
> +bool parse_events_error__contains(const struct parse_events_error *err,
> +				  const char *needle);
>  #ifdef HAVE_LIBELF_SUPPORT
>  /*
>   * If the probe point starts with '%',
> diff --git a/tools/perf/util/parse-events.y b/tools/perf/util/parse-events.y
> index de098caf0c1c..d70f5d84af92 100644
> --- a/tools/perf/util/parse-events.y
> +++ b/tools/perf/util/parse-events.y
> @@ -536,8 +536,6 @@ tracepoint_name opt_event_config
>  	list = alloc_list();
>  	if (!list)
>  		YYNOMEM;
> -	if (error)
> -		error->idx = @1.first_column;
>  
>  	err = parse_events_add_tracepoint(list, &parse_state->idx, $1.sys, $1.event,
>  					error, $2, &@1);