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Re: [PATCH 4/5] perf tools: Propagate error info from tp_format

Started byArnaldo Carvalho de Melo <acme@kernel.org>
First post2015-09-09 23:00 +0200
Last post2015-09-15 04:40 +0200
Articles 9 — 4 participants

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  Re: [PATCH 4/5] perf tools: Propagate error info from tp_format Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-09 23:00 +0200
    Re: [PATCH 4/5] perf tools: Propagate error info from tp_format Jiri Olsa <jolsa@redhat.com> - 2015-09-10 10:30 +0200
      Re: [PATCH 4/5] perf tools: Propagate error info from tp_format Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-10 16:20 +0200
      Re: [PATCH 4/5] perf tools: Propagate error info from tp_format Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-14 23:00 +0200
        Re: [PATCH 4/5] perf tools: Propagate error info from tp_format Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-14 23:10 +0200
        Re: [PATCH 4/5] perf tools: Propagate error info from tp_format Raphaël Beamonte <raphael.beamonte@gmail.com> - 2015-09-14 23:10 +0200
          Re: [PATCH 4/5] perf tools: Propagate error info from tp_format Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com> - 2015-09-14 23:40 +0200
            Re: [PATCH 4/5] perf tools: Propagate error info from tp_format Raphaël Beamonte <raphael.beamonte@gmail.com> - 2015-09-15 00:10 +0200
              Re: [PATCH 4/5] perf tools: Propagate error info from tp_format Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com> - 2015-09-15 04:40 +0200

#1221707 — Re: [PATCH 4/5] perf tools: Propagate error info from tp_format

FromArnaldo Carvalho de Melo <acme@kernel.org>
Date2015-09-09 23:00 +0200
SubjectRe: [PATCH 4/5] perf tools: Propagate error info from tp_format
Message-ID<q6UDg-5Q3-9@gated-at.bofh.it>
Em Mon, Sep 07, 2015 at 10:38:06AM +0200, Jiri Olsa escreveu:
> Propagate error info from tp_format via ERR_PTR to get
> it all the way down to the parse-event.c tracepoint adding
> routines. Following functions now return pointer with
> encoded error:
>   - tp_format
>   - trace_event__tp_format
>   - perf_evsel__newtp_idx
>   - perf_evsel__newtp
> 
> This affects several other places in perf, that cannot use
> pointer check anymore, but must utilize the err.h interface,
> when getting error information from above functions list.

Right, so this is tricky and we must be careful, see below...
 
> Link: http://lkml.kernel.org/n/tip-bzdckgv1zfp2y8up9l7ojt7y@git.kernel.org
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
>  tools/perf/builtin-trace.c                  | 19 +++++++++++--------
>  tools/perf/tests/evsel-tp-sched.c           | 10 ++++++++--
>  tools/perf/tests/openat-syscall-all-cpus.c  |  3 ++-
>  tools/perf/tests/openat-syscall-tp-fields.c |  3 ++-
>  tools/perf/tests/openat-syscall.c           |  3 ++-
>  tools/perf/util/evlist.c                    |  3 ++-
>  tools/perf/util/evsel.c                     | 11 +++++++++--
>  tools/perf/util/evsel.h                     |  3 +++
>  tools/perf/util/parse-events.c              |  6 +++---
>  tools/perf/util/trace-event.c               | 13 +++++++++++--
>  10 files changed, 53 insertions(+), 21 deletions(-)
> 
> diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
> index 215653274102..93b80f12f35e 100644
> --- a/tools/perf/builtin-trace.c
> +++ b/tools/perf/builtin-trace.c
> @@ -38,6 +38,7 @@
>  #include <stdlib.h>
>  #include <sys/mman.h>
>  #include <linux/futex.h>
> +#include <linux/err.h>
>  
>  /* For older distros: */
>  #ifndef MAP_STACK
> @@ -245,13 +246,14 @@ static struct perf_evsel *perf_evsel__syscall_newtp(const char *direction, void
>  	struct perf_evsel *evsel = perf_evsel__newtp("raw_syscalls", direction);
>  
>  	/* older kernel (e.g., RHEL6) use syscalls:{enter,exit} */
> -	if (evsel == NULL)
> +	if (IS_ERR(evsel))
>  		evsel = perf_evsel__newtp("syscalls", direction);
>  
> -	if (evsel) {
> -		if (perf_evsel__init_syscall_tp(evsel, handler))
> -			goto out_delete;
> -	}
> +	if (IS_ERR(evsel))
> +		return NULL;
> +
> +	if (perf_evsel__init_syscall_tp(evsel, handler))
> +		goto out_delete;

This kind of stuff is ok, as evsel is a local variable and you kept the
interface for perf_evsel__syscall_newtp(), i.e. it returns NULL if a new
evsel can't be instantiated.

Ok, but that is a different interface than the one used by
perf_evsel__newtp(), that also instantiates a new evsel.

So when one thinks about "foo__new()" we now need to check which one of
the two interfaces it uses, if err.h or if the old NULL based failure
reporting one.

Double tricky if it is foo__new() and foo__new_variant(), as
perf_evsel__syscall_newtp() and perf_evsel__newtp(), i.e. both will
return a "struct perf_evsel" instance, but one using err.h, the other
use NULL.

Ok, you marked the ones using a comment, wonder if we couldn't use
'sparse' somehow here, is it used to check IS_ERR() usage in the kernel?

Ah, but what about this in trace__event_handler() in builtin-trace.c?
 
        if (evsel->tp_format) {
                event_format__fprintf(evsel->tp_format, sample->cpu,
                                      sample->raw_data, sample->raw_size,
                                      trace->output);
        }


Don't we have to use IS_ERR() here? Ok, no, because if setting up
evsel->tp_format fails, then that evsel will be destroyed and
perf_evsel__newtp() will return ERR_PTR(), so it is ok not no use
ERR_PTR(evsel->tp_format) because it will only be != NULL when it was
successfully set up.

But then, in perf_evsel__newtp_idx if zalloc() fails we will not return
ERR_PTR(), but instead NULL, a-ha, this one seems to be a real bug, no?

/*
 * Returns pointer with encoded error via <linux/err.h> interface.
 */
struct perf_evsel *perf_evsel__newtp_idx(const char *sys, const char *name, int idx)
{
	struct perf_evsel *evsel = zalloc(perf_evsel__object.size);
	int err = -ENOMEM;

	if (evsel != NULL) {
		struct perf_event_attr attr = {
			.type	       = PERF_TYPE_TRACEPOINT,
			.sample_type   = (PERF_SAMPLE_RAW | PERF_SAMPLE_TIME |
					  PERF_SAMPLE_CPU | PERF_SAMPLE_PERIOD),
		};

		if (asprintf(&evsel->name, "%s:%s", sys, name) < 0)
			goto out_free;

		evsel->tp_format = trace_event__tp_format(sys, name);
		if (IS_ERR(evsel->tp_format)) {
			err = PTR_ERR(evsel->tp_format);
			goto out_free;
		}

		event_attr_init(&attr);
		attr.config = evsel->tp_format->id;
		attr.sample_period = 1;
		perf_evsel__init(evsel, &attr, idx);
	}

	return evsel;

out_free:
	zfree(&evsel->name);
	free(evsel);
	return ERR_PTR(err);
}

>  
>  	return evsel;
>  
> @@ -1705,12 +1707,12 @@ static int trace__read_syscall_info(struct trace *trace, int id)
>  	snprintf(tp_name, sizeof(tp_name), "sys_enter_%s", sc->name);
>  	sc->tp_format = trace_event__tp_format("syscalls", tp_name);
>  
> -	if (sc->tp_format == NULL && sc->fmt && sc->fmt->alias) {
> +	if (IS_ERR(sc->tp_format) && sc->fmt && sc->fmt->alias) {
>  		snprintf(tp_name, sizeof(tp_name), "sys_enter_%s", sc->fmt->alias);
>  		sc->tp_format = trace_event__tp_format("syscalls", tp_name);
>  	}
>  
> -	if (sc->tp_format == NULL)
> +	if (IS_ERR(sc->tp_format))
>  		return -1;
>  
>  	sc->args = sc->tp_format->format.fields;
> @@ -2390,7 +2392,8 @@ static size_t trace__fprintf_thread_summary(struct trace *trace, FILE *fp);
>  static bool perf_evlist__add_vfs_getname(struct perf_evlist *evlist)
>  {
>  	struct perf_evsel *evsel = perf_evsel__newtp("probe", "vfs_getname");
> -	if (evsel == NULL)
> +
> +	if (IS_ERR(evsel))
>  		return false;
>  
>  	if (perf_evsel__field(evsel, "pathname") == NULL) {
> diff --git a/tools/perf/tests/evsel-tp-sched.c b/tools/perf/tests/evsel-tp-sched.c
> index 52162425c969..790e413d9a1f 100644
> --- a/tools/perf/tests/evsel-tp-sched.c
> +++ b/tools/perf/tests/evsel-tp-sched.c
> @@ -1,3 +1,4 @@
> +#include <linux/err.h>
>  #include <traceevent/event-parse.h>
>  #include "evsel.h"
>  #include "tests.h"
> @@ -36,8 +37,8 @@ int test__perf_evsel__tp_sched_test(void)
>  	struct perf_evsel *evsel = perf_evsel__newtp("sched", "sched_switch");
>  	int ret = 0;
>  
> -	if (evsel == NULL) {
> -		pr_debug("perf_evsel__new\n");
> +	if (IS_ERR(evsel)) {
> +		pr_debug("perf_evsel__newtp failed with %ld\n", PTR_ERR(evsel));
>  		return -1;
>  	}
>  
> @@ -66,6 +67,11 @@ int test__perf_evsel__tp_sched_test(void)
>  
>  	evsel = perf_evsel__newtp("sched", "sched_wakeup");
>  
> +	if (IS_ERR(evsel)) {
> +		pr_debug("perf_evsel__newtp failed with %ld\n", PTR_ERR(evsel));
> +		return -1;
> +	}
> +
>  	if (perf_evsel__test_field(evsel, "comm", 16, true))
>  		ret = -1;
>  
> diff --git a/tools/perf/tests/openat-syscall-all-cpus.c b/tools/perf/tests/openat-syscall-all-cpus.c
> index 495d8126b722..9e104a2e973d 100644
> --- a/tools/perf/tests/openat-syscall-all-cpus.c
> +++ b/tools/perf/tests/openat-syscall-all-cpus.c
> @@ -1,4 +1,5 @@
>  #include <api/fs/fs.h>
> +#include <linux/err.h>
>  #include "evsel.h"
>  #include "tests.h"
>  #include "thread_map.h"
> @@ -31,7 +32,7 @@ int test__openat_syscall_event_on_all_cpus(void)
>  	CPU_ZERO(&cpu_set);
>  
>  	evsel = perf_evsel__newtp("syscalls", "sys_enter_openat");
> -	if (evsel == NULL) {
> +	if (IS_ERR(evsel)) {
>  		tracing_path__strerror_open_tp(errno, errbuf, sizeof(errbuf), "syscalls", "sys_enter_openat");
>  		pr_err("%s\n", errbuf);
>  		goto out_thread_map_delete;
> diff --git a/tools/perf/tests/openat-syscall-tp-fields.c b/tools/perf/tests/openat-syscall-tp-fields.c
> index 01a19626c846..473d3869727e 100644
> --- a/tools/perf/tests/openat-syscall-tp-fields.c
> +++ b/tools/perf/tests/openat-syscall-tp-fields.c
> @@ -1,3 +1,4 @@
> +#include <linux/err.h>
>  #include "perf.h"
>  #include "evlist.h"
>  #include "evsel.h"
> @@ -30,7 +31,7 @@ int test__syscall_openat_tp_fields(void)
>  	}
>  
>  	evsel = perf_evsel__newtp("syscalls", "sys_enter_openat");
> -	if (evsel == NULL) {
> +	if (IS_ERR(evsel)) {
>  		pr_debug("%s: perf_evsel__newtp\n", __func__);
>  		goto out_delete_evlist;
>  	}
> diff --git a/tools/perf/tests/openat-syscall.c b/tools/perf/tests/openat-syscall.c
> index 08ac9d94a050..7b1db8306098 100644
> --- a/tools/perf/tests/openat-syscall.c
> +++ b/tools/perf/tests/openat-syscall.c
> @@ -1,4 +1,5 @@
>  #include <api/fs/tracing_path.h>
> +#include <linux/err.h>
>  #include "thread_map.h"
>  #include "evsel.h"
>  #include "debug.h"
> @@ -19,7 +20,7 @@ int test__openat_syscall_event(void)
>  	}
>  
>  	evsel = perf_evsel__newtp("syscalls", "sys_enter_openat");
> -	if (evsel == NULL) {
> +	if (IS_ERR(evsel)) {
>  		tracing_path__strerror_open_tp(errno, errbuf, sizeof(errbuf), "syscalls", "sys_enter_openat");
>  		pr_err("%s\n", errbuf);
>  		goto out_thread_map_delete;
> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> index d51a5200c8af..3cb2bf9bd4bd 100644
> --- a/tools/perf/util/evlist.c
> +++ b/tools/perf/util/evlist.c
> @@ -25,6 +25,7 @@
>  #include <linux/bitops.h>
>  #include <linux/hash.h>
>  #include <linux/log2.h>
> +#include <linux/err.h>
>  
>  static void perf_evlist__mmap_put(struct perf_evlist *evlist, int idx);
>  static void __perf_evlist__munmap(struct perf_evlist *evlist, int idx);
> @@ -265,7 +266,7 @@ int perf_evlist__add_newtp(struct perf_evlist *evlist,
>  {
>  	struct perf_evsel *evsel = perf_evsel__newtp(sys, name);
>  
> -	if (evsel == NULL)
> +	if (IS_ERR(evsel))
>  		return -1;
>  
>  	evsel->handler = handler;
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index 771ade4d5966..08c20ee4e27d 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -13,6 +13,7 @@
>  #include <traceevent/event-parse.h>
>  #include <linux/hw_breakpoint.h>
>  #include <linux/perf_event.h>
> +#include <linux/err.h>
>  #include <sys/resource.h>
>  #include "asm/bug.h"
>  #include "callchain.h"
> @@ -225,9 +226,13 @@ struct perf_evsel *perf_evsel__new_idx(struct perf_event_attr *attr, int idx)
>  	return evsel;
>  }
>  
> +/*
> + * Returns pointer with encoded error via <linux/err.h> interface.
> + */
>  struct perf_evsel *perf_evsel__newtp_idx(const char *sys, const char *name, int idx)
>  {
>  	struct perf_evsel *evsel = zalloc(perf_evsel__object.size);
> +	int err = -ENOMEM;
>  
>  	if (evsel != NULL) {
>  		struct perf_event_attr attr = {
> @@ -240,8 +245,10 @@ struct perf_evsel *perf_evsel__newtp_idx(const char *sys, const char *name, int
>  			goto out_free;
>  
>  		evsel->tp_format = trace_event__tp_format(sys, name);
> -		if (evsel->tp_format == NULL)
> +		if (IS_ERR(evsel->tp_format)) {
> +			err = PTR_ERR(evsel->tp_format);
>  			goto out_free;
> +		}
>  
>  		event_attr_init(&attr);
>  		attr.config = evsel->tp_format->id;
> @@ -254,7 +261,7 @@ struct perf_evsel *perf_evsel__newtp_idx(const char *sys, const char *name, int
>  out_free:
>  	zfree(&evsel->name);
>  	free(evsel);
> -	return NULL;
> +	return ERR_PTR(err);
>  }
>  
>  const char *perf_evsel__hw_names[PERF_COUNT_HW_MAX] = {
> diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
> index 298e6bbca200..b6e8ff876f17 100644
> --- a/tools/perf/util/evsel.h
> +++ b/tools/perf/util/evsel.h
> @@ -161,6 +161,9 @@ static inline struct perf_evsel *perf_evsel__new(struct perf_event_attr *attr)
>  
>  struct perf_evsel *perf_evsel__newtp_idx(const char *sys, const char *name, int idx);
>  
> +/*
> + * Returns pointer with encoded error via <linux/err.h> interface.
> + */
>  static inline struct perf_evsel *perf_evsel__newtp(const char *sys, const char *name)
>  {
>  	return perf_evsel__newtp_idx(sys, name, 0);
> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> index 1b284b8ad243..c47831c47220 100644
> --- a/tools/perf/util/parse-events.c
> +++ b/tools/perf/util/parse-events.c
> @@ -1,4 +1,5 @@
>  #include <linux/hw_breakpoint.h>
> +#include <linux/err.h>
>  #include "util.h"
>  #include "../perf.h"
>  #include "evlist.h"
> @@ -393,11 +394,10 @@ static int add_tracepoint(struct list_head *list, int *idx,
>  	struct perf_evsel *evsel;
>  
>  	evsel = perf_evsel__newtp_idx(sys_name, evt_name, (*idx)++);
> -	if (!evsel)
> -		return -ENOMEM;
> +	if (IS_ERR(evsel))
> +		return PTR_ERR(evsel);
>  
>  	list_add_tail(&evsel->node, list);
> -
>  	return 0;
>  }
>  
> diff --git a/tools/perf/util/trace-event.c b/tools/perf/util/trace-event.c
> index 2f4996ab313d..8e3a60e3e15f 100644
> --- a/tools/perf/util/trace-event.c
> +++ b/tools/perf/util/trace-event.c
> @@ -7,6 +7,7 @@
>  #include <sys/stat.h>
>  #include <fcntl.h>
>  #include <linux/kernel.h>
> +#include <linux/err.h>
>  #include <traceevent/event-parse.h>
>  #include <api/fs/tracing_path.h>
>  #include "trace-event.h"
> @@ -66,6 +67,9 @@ void trace_event__cleanup(struct trace_event *t)
>  	pevent_free(t->pevent);
>  }
>  
> +/*
> + * Returns pointer with encoded error via <linux/err.h> interface.
> + */
>  static struct event_format*
>  tp_format(const char *sys, const char *name)
>  {
> @@ -74,12 +78,14 @@ tp_format(const char *sys, const char *name)
>  	char path[PATH_MAX];
>  	size_t size;
>  	char *data;
> +	int err;
>  
>  	scnprintf(path, PATH_MAX, "%s/%s/%s/format",
>  		  tracing_events_path, sys, name);
>  
> -	if (filename__read_str(path, &data, &size))
> -		return NULL;
> +	err = filename__read_str(path, &data, &size);
> +	if (err)
> +		return ERR_PTR(err);
>  
>  	pevent_parse_format(pevent, &event, data, size, sys);
>  
> @@ -87,6 +93,9 @@ tp_format(const char *sys, const char *name)
>  	return event;
>  }
>  
> +/*
> + * Returns pointer with encoded error via <linux/err.h> interface.
> + */
>  struct event_format*
>  trace_event__tp_format(const char *sys, const char *name)
>  {
> -- 
> 2.4.3
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#1221998

FromJiri Olsa <jolsa@redhat.com>
Date2015-09-10 10:30 +0200
Message-ID<q75oZ-4nU-7@gated-at.bofh.it>
In reply to#1221707
On Wed, Sep 09, 2015 at 05:58:13PM -0300, Arnaldo Carvalho de Melo wrote:

SNIP

> This kind of stuff is ok, as evsel is a local variable and you kept the
> interface for perf_evsel__syscall_newtp(), i.e. it returns NULL if a new
> evsel can't be instantiated.
> 
> Ok, but that is a different interface than the one used by
> perf_evsel__newtp(), that also instantiates a new evsel.
> 
> So when one thinks about "foo__new()" we now need to check which one of
> the two interfaces it uses, if err.h or if the old NULL based failure
> reporting one.
> 
> Double tricky if it is foo__new() and foo__new_variant(), as
> perf_evsel__syscall_newtp() and perf_evsel__newtp(), i.e. both will
> return a "struct perf_evsel" instance, but one using err.h, the other
> use NULL.
> 
> Ok, you marked the ones using a comment, wonder if we couldn't use
> 'sparse' somehow here, is it used to check IS_ERR() usage in the kernel?

hum, not sure.. will check ;-)

at least we could mark related functions with __must_check
to force the return value check

> 
> Ah, but what about this in trace__event_handler() in builtin-trace.c?
>  
>         if (evsel->tp_format) {
>                 event_format__fprintf(evsel->tp_format, sample->cpu,
>                                       sample->raw_data, sample->raw_size,
>                                       trace->output);
>         }
> 
> 
> Don't we have to use IS_ERR() here? Ok, no, because if setting up
> evsel->tp_format fails, then that evsel will be destroyed and
> perf_evsel__newtp() will return ERR_PTR(), so it is ok not no use
> ERR_PTR(evsel->tp_format) because it will only be != NULL when it was
> successfully set up.
> 
> But then, in perf_evsel__newtp_idx if zalloc() fails we will not return
> ERR_PTR(), but instead NULL, a-ha, this one seems to be a real bug, no?

hate those allocations in declarations.. never do any good ;-)

yep, NULL is not an error, so it's real bug, attached patch should fix it

thanks,
jirka


---
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 08c20ee4e27d..162973bec713 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -256,7 +256,7 @@ struct perf_evsel *perf_evsel__newtp_idx(const char *sys, const char *name, int
 		perf_evsel__init(evsel, &attr, idx);
 	}
 
-	return evsel;
+	return evsel ?: ERR_PTR(err);
 
 out_free:
 	zfree(&evsel->name);
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#1222226

FromArnaldo Carvalho de Melo <acme@kernel.org>
Date2015-09-10 16:20 +0200
Message-ID<q7aRH-3Sb-11@gated-at.bofh.it>
In reply to#1221998
Em Thu, Sep 10, 2015 at 10:24:52AM +0200, Jiri Olsa escreveu:
> On Wed, Sep 09, 2015 at 05:58:13PM -0300, Arnaldo Carvalho de Melo wrote:
> 
> SNIP
> 
> > This kind of stuff is ok, as evsel is a local variable and you kept the
> > interface for perf_evsel__syscall_newtp(), i.e. it returns NULL if a new
> > evsel can't be instantiated.
> > 
> > Ok, but that is a different interface than the one used by
> > perf_evsel__newtp(), that also instantiates a new evsel.
> > 
> > So when one thinks about "foo__new()" we now need to check which one of
> > the two interfaces it uses, if err.h or if the old NULL based failure
> > reporting one.
> > 
> > Double tricky if it is foo__new() and foo__new_variant(), as
> > perf_evsel__syscall_newtp() and perf_evsel__newtp(), i.e. both will
> > return a "struct perf_evsel" instance, but one using err.h, the other
> > use NULL.
> > 
> > Ok, you marked the ones using a comment, wonder if we couldn't use
> > 'sparse' somehow here, is it used to check IS_ERR() usage in the kernel?
> 
> hum, not sure.. will check ;-)
> 
> at least we could mark related functions with __must_check
> to force the return value check

Right, that helps a bit, but not when the test _is already there_,
against NULL.

That is why I thought about sparse, if it was used in the kernel somehow
to check for this, guess either it would notice ERR_PTR using routines
and then auto-mark them for checking if they are being tested using
IS_ERR() or plain NULL, will check, later...

- Arnaldo
 
> > 
> > Ah, but what about this in trace__event_handler() in builtin-trace.c?
> >  
> >         if (evsel->tp_format) {
> >                 event_format__fprintf(evsel->tp_format, sample->cpu,
> >                                       sample->raw_data, sample->raw_size,
> >                                       trace->output);
> >         }
> > 
> > 
> > Don't we have to use IS_ERR() here? Ok, no, because if setting up
> > evsel->tp_format fails, then that evsel will be destroyed and
> > perf_evsel__newtp() will return ERR_PTR(), so it is ok not no use
> > ERR_PTR(evsel->tp_format) because it will only be != NULL when it was
> > successfully set up.
> > 
> > But then, in perf_evsel__newtp_idx if zalloc() fails we will not return
> > ERR_PTR(), but instead NULL, a-ha, this one seems to be a real bug, no?
> 
> hate those allocations in declarations.. never do any good ;-)
> 
> yep, NULL is not an error, so it's real bug, attached patch should fix it
> 
> thanks,
> jirka
> 
> 
> ---
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index 08c20ee4e27d..162973bec713 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -256,7 +256,7 @@ struct perf_evsel *perf_evsel__newtp_idx(const char *sys, const char *name, int
>  		perf_evsel__init(evsel, &attr, idx);
>  	}
>  
> -	return evsel;
> +	return evsel ?: ERR_PTR(err);
>  
>  out_free:
>  	zfree(&evsel->name);
--
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#1224449

FromArnaldo Carvalho de Melo <acme@kernel.org>
Date2015-09-14 23:00 +0200
Message-ID<q8J10-Ci-19@gated-at.bofh.it>
In reply to#1221998
Em Thu, Sep 10, 2015 at 10:24:52AM +0200, Jiri Olsa escreveu:
> On Wed, Sep 09, 2015 at 05:58:13PM -0300, Arnaldo Carvalho de Melo wrote:
> 
> SNIP
> 
> > This kind of stuff is ok, as evsel is a local variable and you kept the
> > interface for perf_evsel__syscall_newtp(), i.e. it returns NULL if a new
> > evsel can't be instantiated.
> > 
> > Ok, but that is a different interface than the one used by
> > perf_evsel__newtp(), that also instantiates a new evsel.
> > 
> > So when one thinks about "foo__new()" we now need to check which one of
> > the two interfaces it uses, if err.h or if the old NULL based failure
> > reporting one.
> > 
> > Double tricky if it is foo__new() and foo__new_variant(), as
> > perf_evsel__syscall_newtp() and perf_evsel__newtp(), i.e. both will
> > return a "struct perf_evsel" instance, but one using err.h, the other
> > use NULL.
> > 
> > Ok, you marked the ones using a comment, wonder if we couldn't use
> > 'sparse' somehow here, is it used to check IS_ERR() usage in the kernel?
> 
> hum, not sure.. will check ;-)
> 
> at least we could mark related functions with __must_check
> to force the return value check
> 
> > 
> > Ah, but what about this in trace__event_handler() in builtin-trace.c?
> >  
> >         if (evsel->tp_format) {
> >                 event_format__fprintf(evsel->tp_format, sample->cpu,
> >                                       sample->raw_data, sample->raw_size,
> >                                       trace->output);
> >         }
> > 
> > 
> > Don't we have to use IS_ERR() here? Ok, no, because if setting up
> > evsel->tp_format fails, then that evsel will be destroyed and
> > perf_evsel__newtp() will return ERR_PTR(), so it is ok not no use
> > ERR_PTR(evsel->tp_format) because it will only be != NULL when it was
> > successfully set up.
> > 
> > But then, in perf_evsel__newtp_idx if zalloc() fails we will not return
> > ERR_PTR(), but instead NULL, a-ha, this one seems to be a real bug, no?
> 
> hate those allocations in declarations.. never do any good ;-)
> 
> yep, NULL is not an error, so it's real bug, attached patch should fix it
> 
> thanks,
> jirka


Ok continuing, found two more problems in this patch, fixed as follows,
merging.

- Arnaldo

diff --git a/tools/perf/tests/mmap-basic.c b/tools/perf/tests/mmap-basic.c
index 666b67a4df9d..4bb0c5d2059d 100644
--- a/tools/perf/tests/mmap-basic.c
+++ b/tools/perf/tests/mmap-basic.c
@@ -65,7 +65,7 @@ int test__basic_mmap(void)
 
 		snprintf(name, sizeof(name), "sys_enter_%s", syscall_names[i]);
 		evsels[i] = perf_evsel__newtp("syscalls", name);
-		if (evsels[i] == NULL) {
+		if (IS_ERR(evsels[i]) == NULL) {
 			pr_debug("perf_evsel__new\n");
 			goto out_delete_evlist;
 		}
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 08c20ee4e27d..6b5d1b509148 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -234,7 +234,9 @@ struct perf_evsel *perf_evsel__newtp_idx(const char *sys, const char *name, int
 	struct perf_evsel *evsel = zalloc(perf_evsel__object.size);
 	int err = -ENOMEM;
 
-	if (evsel != NULL) {
+	if (evsel == NULL) {
+		goto out_err;
+	} else {
 		struct perf_event_attr attr = {
 			.type	       = PERF_TYPE_TRACEPOINT,
 			.sample_type   = (PERF_SAMPLE_RAW | PERF_SAMPLE_TIME |
@@ -261,6 +263,7 @@ struct perf_evsel *perf_evsel__newtp_idx(const char *sys, const char *name, int
 out_free:
 	zfree(&evsel->name);
 	free(evsel);
+out_err:
 	return ERR_PTR(err);
 }
 
diff --git a/tools/perf/util/trace-event.c b/tools/perf/util/trace-event.c
index 8e3a60e3e15f..802bb868d446 100644
--- a/tools/perf/util/trace-event.c
+++ b/tools/perf/util/trace-event.c
@@ -100,7 +100,7 @@ struct event_format*
 trace_event__tp_format(const char *sys, const char *name)
 {
 	if (!tevent_initialized && trace_event__init2())
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	return tp_format(sys, name);
 }
--
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#1224452

FromArnaldo Carvalho de Melo <acme@kernel.org>
Date2015-09-14 23:10 +0200
Message-ID<q8JaF-12P-13@gated-at.bofh.it>
In reply to#1224449
Em Mon, Sep 14, 2015 at 05:53:03PM -0300, Arnaldo Carvalho de Melo escreveu:
> Ok continuing, found two more problems in this patch, fixed as follows,
> merging.
 
> - Arnaldo
 
> +++ b/tools/perf/tests/mmap-basic.c
> @@ -65,7 +65,7 @@ int test__basic_mmap(void)
>  
>  		snprintf(name, sizeof(name), "sys_enter_%s", syscall_names[i]);
>  		evsels[i] = perf_evsel__newtp("syscalls", name);
> -		if (evsels[i] == NULL) {
> +		if (IS_ERR(evsels[i]) == NULL) {

modulo the == NULL ;-)

>  			pr_debug("perf_evsel__new\n");
>  			goto out_delete_evlist;
>  		}
--
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#1224453

FromRaphaël Beamonte <raphael.beamonte@gmail.com>
Date2015-09-14 23:10 +0200
Message-ID<q8JaF-12P-15@gated-at.bofh.it>
In reply to#1224449
2015-09-14 16:53 GMT-04:00 Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>:
> Em Thu, Sep 10, 2015 at 10:24:52AM +0200, Jiri Olsa escreveu:
>> On Wed, Sep 09, 2015 at 05:58:13PM -0300, Arnaldo Carvalho de Melo wrote:
>>
>> SNIP
>>
>> > This kind of stuff is ok, as evsel is a local variable and you kept the
>> > interface for perf_evsel__syscall_newtp(), i.e. it returns NULL if a new
>> > evsel can't be instantiated.
>> >
>> > Ok, but that is a different interface than the one used by
>> > perf_evsel__newtp(), that also instantiates a new evsel.
>> >
>> > So when one thinks about "foo__new()" we now need to check which one of
>> > the two interfaces it uses, if err.h or if the old NULL based failure
>> > reporting one.
>> >
>> > Double tricky if it is foo__new() and foo__new_variant(), as
>> > perf_evsel__syscall_newtp() and perf_evsel__newtp(), i.e. both will
>> > return a "struct perf_evsel" instance, but one using err.h, the other
>> > use NULL.
>> >
>> > Ok, you marked the ones using a comment, wonder if we couldn't use
>> > 'sparse' somehow here, is it used to check IS_ERR() usage in the kernel?
>>
>> hum, not sure.. will check ;-)
>>
>> at least we could mark related functions with __must_check
>> to force the return value check
>>
>> >
>> > Ah, but what about this in trace__event_handler() in builtin-trace.c?
>> >
>> >         if (evsel->tp_format) {
>> >                 event_format__fprintf(evsel->tp_format, sample->cpu,
>> >                                       sample->raw_data, sample->raw_size,
>> >                                       trace->output);
>> >         }
>> >
>> >
>> > Don't we have to use IS_ERR() here? Ok, no, because if setting up
>> > evsel->tp_format fails, then that evsel will be destroyed and
>> > perf_evsel__newtp() will return ERR_PTR(), so it is ok not no use
>> > ERR_PTR(evsel->tp_format) because it will only be != NULL when it was
>> > successfully set up.
>> >
>> > But then, in perf_evsel__newtp_idx if zalloc() fails we will not return
>> > ERR_PTR(), but instead NULL, a-ha, this one seems to be a real bug, no?
>>
>> hate those allocations in declarations.. never do any good ;-)
>>
>> yep, NULL is not an error, so it's real bug, attached patch should fix it
>>
>> thanks,
>> jirka
>
>
> Ok continuing, found two more problems in this patch, fixed as follows,
> merging.
>
> - Arnaldo
>
> diff --git a/tools/perf/tests/mmap-basic.c b/tools/perf/tests/mmap-basic.c
> index 666b67a4df9d..4bb0c5d2059d 100644
> --- a/tools/perf/tests/mmap-basic.c
> +++ b/tools/perf/tests/mmap-basic.c
> @@ -65,7 +65,7 @@ int test__basic_mmap(void)
>
>                 snprintf(name, sizeof(name), "sys_enter_%s", syscall_names[i]);
>                 evsels[i] = perf_evsel__newtp("syscalls", name);
> -               if (evsels[i] == NULL) {
> +               if (IS_ERR(evsels[i]) == NULL) {
>                         pr_debug("perf_evsel__new\n");
>                         goto out_delete_evlist;
>                 }
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index 08c20ee4e27d..6b5d1b509148 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -234,7 +234,9 @@ struct perf_evsel *perf_evsel__newtp_idx(const char *sys, const char *name, int
>         struct perf_evsel *evsel = zalloc(perf_evsel__object.size);
>         int err = -ENOMEM;
>
> -       if (evsel != NULL) {
> +       if (evsel == NULL) {
> +               goto out_err;
> +       } else {

Is the else really necessary after a goto?

>                 struct perf_event_attr attr = {
>                         .type          = PERF_TYPE_TRACEPOINT,
>                         .sample_type   = (PERF_SAMPLE_RAW | PERF_SAMPLE_TIME |
> @@ -261,6 +263,7 @@ struct perf_evsel *perf_evsel__newtp_idx(const char *sys, const char *name, int
>  out_free:
>         zfree(&evsel->name);
>         free(evsel);
> +out_err:
>         return ERR_PTR(err);
>  }
>
> diff --git a/tools/perf/util/trace-event.c b/tools/perf/util/trace-event.c
> index 8e3a60e3e15f..802bb868d446 100644
> --- a/tools/perf/util/trace-event.c
> +++ b/tools/perf/util/trace-event.c
> @@ -100,7 +100,7 @@ struct event_format*
>  trace_event__tp_format(const char *sys, const char *name)
>  {
>         if (!tevent_initialized && trace_event__init2())
> -               return NULL;
> +               return ERR_PTR(-ENOMEM);
>
>         return tp_format(sys, name);
>  }
--
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#1224470

FromArnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
Date2015-09-14 23:40 +0200
Message-ID<q8JDI-1AN-1@gated-at.bofh.it>
In reply to#1224453
Em Mon, Sep 14, 2015 at 04:59:41PM -0400, Raphaël Beamonte escreveu:
> 2015-09-14 16:53 GMT-04:00 Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>:
> > +++ b/tools/perf/util/evsel.c
> > @@ -234,7 +234,9 @@ struct perf_evsel *perf_evsel__newtp_idx(const char *sys, const char *name, int
> >         struct perf_evsel *evsel = zalloc(perf_evsel__object.size);
> >         int err = -ENOMEM;
> >
> > -       if (evsel != NULL) {
> > +       if (evsel == NULL) {
> > +               goto out_err;
> > +       } else {
> 
> Is the else really necessary after a goto?

Not really, we can remove it and all would be equivalent (the code
with/without should be the same), its just that I wanted to avoid
touching the identation to reduce patch size and since we need o open a
brace to declare that attr variable...

- Arnaldo
 
> >                 struct perf_event_attr attr = {
> >                         .type          = PERF_TYPE_TRACEPOINT,
> >                         .sample_type   = (PERF_SAMPLE_RAW | PERF_SAMPLE_TIME |
> > @@ -261,6 +263,7 @@ struct perf_evsel *perf_evsel__newtp_idx(const char *sys, const char *name, int
> >  out_free:
> >         zfree(&evsel->name);
> >         free(evsel);
> > +out_err:
> >         return ERR_PTR(err);
> >  }
> >
> > diff --git a/tools/perf/util/trace-event.c b/tools/perf/util/trace-event.c
> > index 8e3a60e3e15f..802bb868d446 100644
> > --- a/tools/perf/util/trace-event.c
> > +++ b/tools/perf/util/trace-event.c
> > @@ -100,7 +100,7 @@ struct event_format*
> >  trace_event__tp_format(const char *sys, const char *name)
> >  {
> >         if (!tevent_initialized && trace_event__init2())
> > -               return NULL;
> > +               return ERR_PTR(-ENOMEM);
> >
> >         return tp_format(sys, name);
> >  }
--
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#1224493

FromRaphaël Beamonte <raphael.beamonte@gmail.com>
Date2015-09-15 00:10 +0200
Message-ID<q8K6K-2nU-17@gated-at.bofh.it>
In reply to#1224470
2015-09-14 17:36 GMT-04:00 Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>:
> Em Mon, Sep 14, 2015 at 04:59:41PM -0400, Raphaël Beamonte escreveu:
>> 2015-09-14 16:53 GMT-04:00 Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>:
>> > +++ b/tools/perf/util/evsel.c
>> > @@ -234,7 +234,9 @@ struct perf_evsel *perf_evsel__newtp_idx(const char *sys, const char *name, int
>> >         struct perf_evsel *evsel = zalloc(perf_evsel__object.size);
>> >         int err = -ENOMEM;
>> >
>> > -       if (evsel != NULL) {
>> > +       if (evsel == NULL) {
>> > +               goto out_err;
>> > +       } else {
>>
>> Is the else really necessary after a goto?
>
> Not really, we can remove it and all would be equivalent (the code
> with/without should be the same), its just that I wanted to avoid
> touching the identation to reduce patch size and since we need o open a
> brace to declare that attr variable...
>
> - Arnaldo

Ok. Though, given the content of that function, we could probably
declare attr in the first lines of the function and assign it its
value after the if. But I understand the patch size argument! :o)
On another subject, but on the same lines, shouldn't we use if
(!evsel) instead of if (evsel == NULL)? (kernel code style if I'm not
mistaken) Or is there something that prevents from using it here?

>> >                 struct perf_event_attr attr = {
>> >                         .type          = PERF_TYPE_TRACEPOINT,
>> >                         .sample_type   = (PERF_SAMPLE_RAW | PERF_SAMPLE_TIME |
>> > @@ -261,6 +263,7 @@ struct perf_evsel *perf_evsel__newtp_idx(const char *sys, const char *name, int
>> >  out_free:
>> >         zfree(&evsel->name);
>> >         free(evsel);
>> > +out_err:
>> >         return ERR_PTR(err);
>> >  }
>> >
>> > diff --git a/tools/perf/util/trace-event.c b/tools/perf/util/trace-event.c
>> > index 8e3a60e3e15f..802bb868d446 100644
>> > --- a/tools/perf/util/trace-event.c
>> > +++ b/tools/perf/util/trace-event.c
>> > @@ -100,7 +100,7 @@ struct event_format*
>> >  trace_event__tp_format(const char *sys, const char *name)
>> >  {
>> >         if (!tevent_initialized && trace_event__init2())
>> > -               return NULL;
>> > +               return ERR_PTR(-ENOMEM);
>> >
>> >         return tp_format(sys, name);
>> >  }
--
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#1224602

FromArnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
Date2015-09-15 04:40 +0200
Message-ID<q8Ok2-8ll-1@gated-at.bofh.it>
In reply to#1224493
Em Mon, Sep 14, 2015 at 06:05:38PM -0400, Raphaël Beamonte escreveu:
> 2015-09-14 17:36 GMT-04:00 Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>:
> > Em Mon, Sep 14, 2015 at 04:59:41PM -0400, Raphaël Beamonte escreveu:
> >> 2015-09-14 16:53 GMT-04:00 Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>:
> >> > +++ b/tools/perf/util/evsel.c
> >> > @@ -234,7 +234,9 @@ struct perf_evsel *perf_evsel__newtp_idx(const char *sys, const char *name, int
> >> >         struct perf_evsel *evsel = zalloc(perf_evsel__object.size);
> >> >         int err = -ENOMEM;
> >> >
> >> > -       if (evsel != NULL) {
> >> > +       if (evsel == NULL) {
> >> > +               goto out_err;
> >> > +       } else {
> >>
> >> Is the else really necessary after a goto?
> >
> > Not really, we can remove it and all would be equivalent (the code
> > with/without should be the same), its just that I wanted to avoid
> > touching the identation to reduce patch size and since we need o open a
> > brace to declare that attr variable...
> 
> Ok. Though, given the content of that function, we could probably
> declare attr in the first lines of the function and assign it its
> value after the if. But I understand the patch size argument! :o)

Yeah, in other times I would have cleaned it all up, having that else is
ugly, but review time is more expensive, I think, so we need to reduce
its cost.

Cleaning it up makes it easier to read, but we get the info about when
that particular code was written buried a bit below the reindentation
cset.

Would be nice to have a 'git blame' that would just unwind things like
that :-)

> On another subject, but on the same lines, shouldn't we use if
> (!evsel) instead of if (evsel == NULL)? (kernel code style if I'm not
> mistaken) Or is there something that prevents from using it here?

I'd say both are ok. (evsel) is shorter than (evsel != NULL), but the
later is more expressive, at a glance you know it is a pointer, etc.

- Arnaldo
 
> >> >                 struct perf_event_attr attr = {
> >> >                         .type          = PERF_TYPE_TRACEPOINT,
> >> >                         .sample_type   = (PERF_SAMPLE_RAW | PERF_SAMPLE_TIME |
> >> > @@ -261,6 +263,7 @@ struct perf_evsel *perf_evsel__newtp_idx(const char *sys, const char *name, int
> >> >  out_free:
> >> >         zfree(&evsel->name);
> >> >         free(evsel);
> >> > +out_err:
> >> >         return ERR_PTR(err);
> >> >  }
> >> >
> >> > diff --git a/tools/perf/util/trace-event.c b/tools/perf/util/trace-event.c
> >> > index 8e3a60e3e15f..802bb868d446 100644
> >> > --- a/tools/perf/util/trace-event.c
> >> > +++ b/tools/perf/util/trace-event.c
> >> > @@ -100,7 +100,7 @@ struct event_format*
> >> >  trace_event__tp_format(const char *sys, const char *name)
> >> >  {
> >> >         if (!tevent_initialized && trace_event__init2())
> >> > -               return NULL;
> >> > +               return ERR_PTR(-ENOMEM);
> >> >
> >> >         return tp_format(sys, name);
> >> >  }
--
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