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