Sorry for disturb you! maybe my question isn't a good question, but I do want to know what situation made dwarf callchain unwind process concurrently, can you guys give a example to elaborate on that. thank you very much!
On Mon, May 18, 2015 at 11:50 PM, Arnaldo Carvalho de Melo <a...@kernel.org> wrote: > From: Namhyung Kim <namhy...@kernel.org> > > The dso cache is accessed during dwarf callchain unwind and it might be > processed concurrently. Protect it under dso->lock. > > Note that it doesn't protect dso_cache__find(). I think it's safe to > access to the cache tree without the lock since we don't delete nodes. > > It it missed an existing node due to rotation, it'll find it during > dso_cache__insert() anyway. > > Signed-off-by: Namhyung Kim <namhy...@kernel.org> > Cc: Adrian Hunter <adrian.hun...@intel.com> > Cc: Andi Kleen <a...@firstfloor.org> > Cc: David Ahern <dsah...@gmail.com> > Cc: Frederic Weisbecker <fweis...@gmail.com> > Cc: Jiri Olsa <jo...@redhat.com> > Cc: Peter Zijlstra <a.p.zijls...@chello.nl> > Cc: Stephane Eranian <eran...@google.com> > Link: > http://lkml.kernel.org/r/1431909055-21442-27-git-send-email-namhy...@kernel.org > Signed-off-by: Arnaldo Carvalho de Melo <a...@redhat.com> > --- > tools/perf/util/dso.c | 34 +++++++++++++++++++++++++++------- > 1 file changed, 27 insertions(+), 7 deletions(-) > > diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c > index 482d6024ef13..666e1db44541 100644 > --- a/tools/perf/util/dso.c > +++ b/tools/perf/util/dso.c > @@ -495,10 +495,12 @@ bool dso__data_status_seen(struct dso *dso, enum > dso_data_status_seen by) > } > > static void > -dso_cache__free(struct rb_root *root) > +dso_cache__free(struct dso *dso) > { > + struct rb_root *root = &dso->data.cache; > struct rb_node *next = rb_first(root); > > + pthread_mutex_lock(&dso->lock); > while (next) { > struct dso_cache *cache; > > @@ -507,10 +509,12 @@ dso_cache__free(struct rb_root *root) > rb_erase(&cache->rb_node, root); > free(cache); > } > + pthread_mutex_unlock(&dso->lock); > } > > -static struct dso_cache *dso_cache__find(const struct rb_root *root, u64 > offset) > +static struct dso_cache *dso_cache__find(struct dso *dso, u64 offset) > { > + const struct rb_root *root = &dso->data.cache; > struct rb_node * const *p = &root->rb_node; > const struct rb_node *parent = NULL; > struct dso_cache *cache; > @@ -529,17 +533,20 @@ static struct dso_cache *dso_cache__find(const struct > rb_root *root, u64 offset) > else > return cache; > } > + > return NULL; > } > > -static void > -dso_cache__insert(struct rb_root *root, struct dso_cache *new) > +static struct dso_cache * > +dso_cache__insert(struct dso *dso, struct dso_cache *new) > { > + struct rb_root *root = &dso->data.cache; > struct rb_node **p = &root->rb_node; > struct rb_node *parent = NULL; > struct dso_cache *cache; > u64 offset = new->offset; > > + pthread_mutex_lock(&dso->lock); > while (*p != NULL) { > u64 end; > > @@ -551,10 +558,17 @@ dso_cache__insert(struct rb_root *root, struct > dso_cache *new) > p = &(*p)->rb_left; > else if (offset >= end) > p = &(*p)->rb_right; > + else > + goto out; > } > > rb_link_node(&new->rb_node, parent, p); > rb_insert_color(&new->rb_node, root); > + > + cache = NULL; > +out: > + pthread_mutex_unlock(&dso->lock); > + return cache; > } > > static ssize_t > @@ -572,6 +586,7 @@ static ssize_t > dso_cache__read(struct dso *dso, u64 offset, u8 *data, ssize_t size) > { > struct dso_cache *cache; > + struct dso_cache *old; > ssize_t ret; > > do { > @@ -591,7 +606,12 @@ dso_cache__read(struct dso *dso, u64 offset, u8 *data, > ssize_t size) > > cache->offset = cache_offset; > cache->size = ret; > - dso_cache__insert(&dso->data.cache, cache); > + old = dso_cache__insert(dso, cache); > + if (old) { > + /* we lose the race */ > + free(cache); > + cache = old; > + } > > ret = dso_cache__memcpy(cache, offset, data, size); > > @@ -608,7 +628,7 @@ static ssize_t dso_cache_read(struct dso *dso, u64 offset, > { > struct dso_cache *cache; > > - cache = dso_cache__find(&dso->data.cache, offset); > + cache = dso_cache__find(dso, offset); > if (cache) > return dso_cache__memcpy(cache, offset, data, size); > else > @@ -964,7 +984,7 @@ void dso__delete(struct dso *dso) > > dso__data_close(dso); > auxtrace_cache__free(dso->auxtrace_cache); > - dso_cache__free(&dso->data.cache); > + dso_cache__free(dso); > dso__free_a2l(dso); > zfree(&dso->symsrc_filename); > pthread_mutex_destroy(&dso->lock); > -- > 2.1.0 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- Best Regards Bryton.Lee
