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    Subject[PATCH 02/38] perf evlist: Send the errno in the signal when workload fails
    Date
    From: Arnaldo Carvalho de Melo <acme@redhat.com>

    When a tool uses perf_evlist__start_workload and the supplied workload
    fails (e.g.: its binary wasn't found), perror was being used to print
    the error reason.

    This is undesirable, as the caller may be a GUI, when it wants to have
    total control of the error reporting process.

    So move to using sigaction(SA_SIGINFO) + siginfo_t->sa_value->sival_int
    to communicate to the caller the errno and let it print it using the UI
    of its choosing.

    Cc: Adrian Hunter <adrian.hunter@intel.com>
    Cc: David Ahern <dsahern@gmail.com>
    Cc: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Jiri Olsa <jolsa@redhat.com>
    Cc: Mike Galbraith <efault@gmx.de>
    Cc: Namhyung Kim <namhyung@kernel.org>
    Cc: Paul Mackerras <paulus@samba.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Stephane Eranian <eranian@google.com>
    Link: http://lkml.kernel.org/n/tip-epgcv7kjq8ll2udqfken92pz@git.kernel.org
    Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
    ---
    tools/perf/builtin-record.c | 39 +++++++++++++++++++++++++++++++++++++--
    tools/perf/builtin-stat.c | 21 +++++++++++++++------
    tools/perf/util/evlist.c | 11 ++++++++---
    3 files changed, 60 insertions(+), 11 deletions(-)

    diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
    index 6ec0cbc2a5d5..f987d385c6f0 100644
    --- a/tools/perf/builtin-record.c
    +++ b/tools/perf/builtin-record.c
    @@ -341,6 +341,22 @@ static void record__init_features(struct record *rec)
    perf_header__clear_feat(&session->header, HEADER_BRANCH_STACK);
    }

    +static volatile int workload_exec_errno;
    +
    +/*
    + * perf_evlist__prepare_workload will send a SIGUSR1
    + * if the fork fails, since we asked by setting its
    + * want_signal to true.
    + */
    +static void workload_exec_failed_signal(int signo, siginfo_t *info,
    + void *ucontext __maybe_unused)
    +{
    + workload_exec_errno = info->si_value.sival_int;
    + done = 1;
    + signr = signo;
    + child_finished = 1;
    +}
    +
    static int __cmd_record(struct record *rec, int argc, const char **argv)
    {
    int err;
    @@ -359,7 +375,6 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
    on_exit(record__sig_exit, rec);
    signal(SIGCHLD, sig_handler);
    signal(SIGINT, sig_handler);
    - signal(SIGUSR1, sig_handler);
    signal(SIGTERM, sig_handler);

    session = perf_session__new(file, false, NULL);
    @@ -492,8 +507,20 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
    /*
    * Let the child rip
    */
    - if (forks)
    + if (forks) {
    + struct sigaction act = {
    + .sa_flags = SA_SIGINFO,
    + .sa_sigaction = workload_exec_failed_signal,
    + };
    + /*
    + * perf_evlist__prepare_workload will, after we call
    + * perf_evlist__start_Workload, send a SIGUSR1 if the exec call
    + * fails, that we will catch in workload_signal to flip
    + * workload_exec_errno.
    + */
    + sigaction(SIGUSR1, &act, NULL);
    perf_evlist__start_workload(evsel_list);
    + }

    for (;;) {
    int hits = rec->samples;
    @@ -521,6 +548,14 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
    }
    }

    + if (forks && workload_exec_errno) {
    + char msg[512];
    + const char *emsg = strerror_r(workload_exec_errno, msg, sizeof(msg));
    + pr_err("Workload failed: %s\n", emsg);
    + err = -1;
    + goto out_delete_session;
    + }
    +
    if (quiet || signr == SIGUSR1)
    return 0;

    diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
    index 1c76c7a66f78..9d0d52d55ee6 100644
    --- a/tools/perf/builtin-stat.c
    +++ b/tools/perf/builtin-stat.c
    @@ -58,6 +58,7 @@
    #include "util/thread.h"
    #include "util/thread_map.h"

    +#include <signal.h>
    #include <stdlib.h>
    #include <sys/prctl.h>
    #include <locale.h>
    @@ -509,16 +510,17 @@ static void handle_initial_delay(void)
    }
    }

    -static volatile bool workload_exec_failed;
    +static volatile int workload_exec_errno;

    /*
    * perf_evlist__prepare_workload will send a SIGUSR1
    * if the fork fails, since we asked by setting its
    * want_signal to true.
    */
    -static void workload_exec_failed_signal(int signo __maybe_unused)
    +static void workload_exec_failed_signal(int signo __maybe_unused, siginfo_t *info,
    + void *ucontext __maybe_unused)
    {
    - workload_exec_failed = true;
    + workload_exec_errno = info->si_value.sival_int;
    }

    static int __run_perf_stat(int argc, const char **argv)
    @@ -596,13 +598,17 @@ static int __run_perf_stat(int argc, const char **argv)
    clock_gettime(CLOCK_MONOTONIC, &ref_time);

    if (forks) {
    + struct sigaction act = {
    + .sa_flags = SA_SIGINFO,
    + .sa_sigaction = workload_exec_failed_signal,
    + };
    /*
    * perf_evlist__prepare_workload will, after we call
    * perf_evlist__start_Workload, send a SIGUSR1 if the exec call
    * fails, that we will catch in workload_signal to flip
    - * workload_exec_failed.
    + * workload_exec_errno.
    */
    - signal(SIGUSR1, workload_exec_failed_signal);
    + sigaction(SIGUSR1, &act, NULL);

    perf_evlist__start_workload(evsel_list);
    handle_initial_delay();
    @@ -615,8 +621,11 @@ static int __run_perf_stat(int argc, const char **argv)
    }
    wait(&status);

    - if (workload_exec_failed)
    + if (workload_exec_errno) {
    + const char *emsg = strerror_r(workload_exec_errno, msg, sizeof(msg));
    + pr_err("Workload failed: %s\n", emsg);
    return -1;
    + }

    if (WIFSIGNALED(status))
    psignal(WTERMSIG(status), argv[0]);
    diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
    index b08a7ecdcea1..4a30c87d24ec 100644
    --- a/tools/perf/util/evlist.c
    +++ b/tools/perf/util/evlist.c
    @@ -1073,9 +1073,14 @@ int perf_evlist__prepare_workload(struct perf_evlist *evlist, struct target *tar

    execvp(argv[0], (char **)argv);

    - perror(argv[0]);
    - if (want_signal)
    - kill(getppid(), SIGUSR1);
    + if (want_signal) {
    + union sigval val;
    +
    + val.sival_int = errno;
    + if (sigqueue(getppid(), SIGUSR1, val))
    + perror(argv[0]);
    + } else
    + perror(argv[0]);
    exit(-1);
    }

    --
    1.8.1.4


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