malloc_trim: clean up idle arenas immediately

There's no need to worry about race conditions if operating on
idle arenas, so clean them up immediately rather than cleaning
them up after a pthread_create (which may never come).

We'll also inform active threads about the trim earlier so they
have more cycles to react to the lazy trim request.

1 files changed, 18 insertions, 11 deletions

diff --git a/mymalloc.h b/mymalloc.h
index e789cf3..4904b74 100644
--- a/mymalloc.h
+++ b/mymalloc.h
@@ -150,23 +150,30 @@ static void remote_free_finish(mstate ms)
 
 int malloc_trim(size_t pad)
 {
-        mstate ms = ms_tsd;
+        mstate m;
+        int ret = 0;
 
         CHECK(int, 0, pthread_mutex_lock(&global_mtx));
-        { /* be lazy for sibling threads, readers are not synchronized */
-                mstate m;
-                cds_list_for_each_entry(m, &arenas_unused, arena_node)
-                        uatomic_set(&m->trim_check, 0);
-                cds_list_for_each_entry(m, &arenas_active, arena_node)
-                        uatomic_set(&m->trim_check, 0);
+
+        /* be lazy for active sibling threads, readers are not synchronized */
+        cds_list_for_each_entry(m, &arenas_active, arena_node)
+                uatomic_set(&m->trim_check, 0);
+
+        /* nobody is using idle arenas, clean immediately */
+        cds_list_for_each_entry(m, &arenas_unused, arena_node) {
+                m->trim_check = 0;
+                remote_free_finish(m);
+                ret |= sys_trim(m, pad);
         }
+
         CHECK(int, 0, pthread_mutex_unlock(&global_mtx));
 
-        if (ms) { /* trim our own arena immediately */
-                remote_free_finish(ms);
-                return sys_trim(ms, pad);
+        m = ms_tsd;
+        if (m) { /* trim our own arena immediately */
+                remote_free_finish(m);
+                ret |= sys_trim(m, pad);
         }
-        return 0;
+        return ret;
 }
 
 static void remote_free_enqueue(mstate fm, void *mem)