Re: [PATCH v2] perf pmu: Make parser reentrant

[Ian Rogers]

On Wed, Apr 5, 2023 at 2:23 PM Jiri Olsa <olsajiri@xxxxxxxxx> wrote:
>
> On Tue, Apr 04, 2023 at 06:36:30AM -0700, Ian Rogers wrote:
> > By default bison uses global state for compatibility with yacc. Make
> > the parser reentrant so that it may be used in asynchronous and
> > multithreaded situations.
> >
> > Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
> > ---
> >  tools/perf/util/pmu.c | 24 ++++++++++++++++++------
> >  tools/perf/util/pmu.h |  2 +-
> >  tools/perf/util/pmu.l | 17 ++++++++++++-----
> >  tools/perf/util/pmu.y |  5 ++++-
> >  4 files changed, 35 insertions(+), 13 deletions(-)
> >
> > diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
> > index 78a407b42ad1..f603cdabf797 100644
> > --- a/tools/perf/util/pmu.c
> > +++ b/tools/perf/util/pmu.c
> > @@ -24,6 +24,8 @@
> >  #include "evsel.h"
> >  #include "pmu.h"
> >  #include "pmus.h"
> > +#include "pmu-bison.h"
> > +#include "pmu-flex.h"
> >  #include "parse-events.h"
> >  #include "print-events.h"
> >  #include "header.h"
> > @@ -57,9 +59,6 @@ struct perf_pmu_format {
> >       struct list_head list;
> >  };
> >
> > -int perf_pmu_parse(struct list_head *list, char *name);
> > -extern FILE *perf_pmu_in;
> > -
> >  static bool hybrid_scanned;
> >
> >  static struct perf_pmu *perf_pmu__find2(int dirfd, const char *name);
> > @@ -81,6 +80,8 @@ int perf_pmu__format_parse(int dirfd, struct list_head *head)
> >       while (!ret && (evt_ent = readdir(format_dir))) {
> >               char *name = evt_ent->d_name;
> >               int fd;
> > +             void *scanner;
> > +             FILE *file;
> >
> >               if (!strcmp(name, ".") || !strcmp(name, ".."))
> >                       continue;
> > @@ -91,9 +92,20 @@ int perf_pmu__format_parse(int dirfd, struct list_head *head)
> >               if (fd < 0)
> >                       break;
> >
> > -             perf_pmu_in = fdopen(fd, "r");
> > -             ret = perf_pmu_parse(head, name);
> > -             fclose(perf_pmu_in);
> > +             file = fdopen(fd, "r");
> > +             if (!file)
> > +                     break;
>
> hum, do we potentially leak fd in here?
>
> jirka

Agreed. Will fix in v3.

Thanks,
Ian

> > +
> > +             ret = perf_pmu_lex_init(&scanner);
> > +             if (ret) {
> > +                     fclose(file);
> > +                     break;
> > +             }
> > +
> > +             perf_pmu_set_in(file, scanner);
> > +             ret = perf_pmu_parse(head, name, scanner);
> > +             perf_pmu_lex_destroy(scanner);
> > +             fclose(file);
> >       }
> >
> >       closedir(format_dir);
> > diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
> > index 32c3a75bca0e..d53618c65c92 100644
> > --- a/tools/perf/util/pmu.h
> > +++ b/tools/perf/util/pmu.h
> > @@ -206,7 +206,7 @@ int perf_pmu__check_alias(struct perf_pmu *pmu, struct list_head *head_terms,
> >                         struct perf_pmu_info *info);
> >  struct list_head *perf_pmu__alias(struct perf_pmu *pmu,
> >                                 struct list_head *head_terms);
> > -void perf_pmu_error(struct list_head *list, char *name, char const *msg);
> > +void perf_pmu_error(struct list_head *list, char *name, void *scanner, char const *msg);
> >
> >  int perf_pmu__new_format(struct list_head *list, char *name,
> >                        int config, unsigned long *bits);
> > diff --git a/tools/perf/util/pmu.l b/tools/perf/util/pmu.l
> > index 58b4926cfaca..67b247be693b 100644
> > --- a/tools/perf/util/pmu.l
> > +++ b/tools/perf/util/pmu.l
> > @@ -1,4 +1,6 @@
> >  %option prefix="perf_pmu_"
> > +%option reentrant
> > +%option bison-bridge
> >
> >  %{
> >  #include <stdlib.h>
> > @@ -6,16 +8,21 @@
> >  #include "pmu.h"
> >  #include "pmu-bison.h"
> >
> > -static int value(int base)
> > +char *perf_pmu_get_text(yyscan_t yyscanner);
> > +YYSTYPE *perf_pmu_get_lval(yyscan_t yyscanner);
> > +
> > +static int value(yyscan_t scanner, int base)
> >  {
> > +     YYSTYPE *yylval = perf_pmu_get_lval(scanner);
> > +     char *text = perf_pmu_get_text(scanner);
> >       long num;
> >
> >       errno = 0;
> > -     num = strtoul(perf_pmu_text, NULL, base);
> > +     num = strtoul(text, NULL, base);
> >       if (errno)
> >               return PP_ERROR;
> >
> > -     perf_pmu_lval.num = num;
> > +     yylval->num = num;
> >       return PP_VALUE;
> >  }
> >
> > @@ -25,7 +32,7 @@ num_dec         [0-9]+
> >
> >  %%
> >
> > -{num_dec}    { return value(10); }
> > +{num_dec}    { return value(yyscanner, 10); }
> >  config               { return PP_CONFIG; }
> >  -            { return '-'; }
> >  :            { return ':'; }
> > @@ -35,7 +42,7 @@ config              { return PP_CONFIG; }
> >
> >  %%
> >
> > -int perf_pmu_wrap(void)
> > +int perf_pmu_wrap(void *scanner __maybe_unused)
> >  {
> >       return 1;
> >  }
> > diff --git a/tools/perf/util/pmu.y b/tools/perf/util/pmu.y
> > index e675d79a0274..dff4e892ac4d 100644
> > --- a/tools/perf/util/pmu.y
> > +++ b/tools/perf/util/pmu.y
> > @@ -1,6 +1,8 @@
> > -
> > +%define api.pure full
> >  %parse-param {struct list_head *format}
> >  %parse-param {char *name}
> > +%parse-param {void *scanner}
> > +%lex-param {void* scanner}
> >
> >  %{
> >
> > @@ -78,6 +80,7 @@ PP_VALUE
> >
> >  void perf_pmu_error(struct list_head *list __maybe_unused,
> >                   char *name __maybe_unused,
> > +                 void *scanner __maybe_unused,
> >                   char const *msg __maybe_unused)
> >  {
> >  }
> > --
> > 2.40.0.348.gf938b09366-goog
> >