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

From: Arnaldo Carvalho de Melo
Date: Wed Sep 09 2015 - 16:58:26 EST

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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@xxxxxxxxxxxxxx
> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> ---
> 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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Next message: Palmer Dabbelt: "Re: [PATCH] Remove #ifdef CONFIG_64BIT from all asm-generic/fcntl.h"
Previous message: Sergei Trofimovich: "[PATCH] net/mac80211/rate.c: fix wrong sizeof()"
Next in thread: Jiri Olsa: "Re: [PATCH 4/5] perf tools: Propagate error info from tp_format"
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