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    SubjectRe: [PATCH 27/42] perf tools: Protect dso symbol loading using a mutex
    Em Thu, Jan 29, 2015 at 05:07:08PM +0900, Namhyung Kim escreveu:
    > When multi-thread support for perf report is enabled, it's possible to
    > access a dso concurrently. Add a new pthread_mutex to protect it from
    > concurrent dso__load().
    >
    > Signed-off-by: Namhyung Kim <namhyung@kernel.org>
    > ---
    > tools/perf/util/dso.c | 2 ++
    > tools/perf/util/dso.h | 1 +
    > tools/perf/util/symbol.c | 34 ++++++++++++++++++++++++----------
    > 3 files changed, 27 insertions(+), 10 deletions(-)
    >
    > diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
    > index 45be944d450a..3da75816b8f8 100644
    > --- a/tools/perf/util/dso.c
    > +++ b/tools/perf/util/dso.c
    > @@ -888,6 +888,7 @@ struct dso *dso__new(const char *name)
    > RB_CLEAR_NODE(&dso->rb_node);
    > INIT_LIST_HEAD(&dso->node);
    > INIT_LIST_HEAD(&dso->data.open_entry);
    > + pthread_mutex_init(&dso->lock, NULL);
    > }
    >
    > return dso;
    > @@ -917,6 +918,7 @@ void dso__delete(struct dso *dso)
    > dso_cache__free(&dso->data.cache);
    > dso__free_a2l(dso);
    > zfree(&dso->symsrc_filename);
    > + pthread_mutex_destroy(&dso->lock);
    > free(dso);
    > }
    >
    > diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
    > index 3782c82c6e44..ac753594a469 100644
    > --- a/tools/perf/util/dso.h
    > +++ b/tools/perf/util/dso.h
    > @@ -102,6 +102,7 @@ struct dsos {
    > };
    >
    > struct dso {
    > + pthread_mutex_t lock;
    > struct list_head node;
    > struct rb_node rb_node; /* rbtree node sorted by long name */
    > struct rb_root symbols[MAP__NR_TYPES];
    > diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
    > index a69066865a55..714e20c99354 100644
    > --- a/tools/perf/util/symbol.c
    > +++ b/tools/perf/util/symbol.c
    > @@ -1357,12 +1357,22 @@ int dso__load(struct dso *dso, struct map *map, symbol_filter_t filter)
    > struct symsrc *syms_ss = NULL, *runtime_ss = NULL;
    > bool kmod;
    >
    > - dso__set_loaded(dso, map->type);
    > + pthread_mutex_lock(&dso->lock);
    > +
    > + /* check again under the dso->lock */

    Again? Where was it first checked? Perhaps we should lock there, so that
    we don't have to do two checks, one unlocked, the other locked?

    > + if (dso__loaded(dso, map->type)) {
    > + ret = 1;
    > + goto out;
    > + }
    > +

    - Arnaldo


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